Target Groups Of H1n1 A Influenza Biology Essay


People who had underlying medical conditions such as asthma, pulmonary diseases, HIV, or immunosuppressant are most at risk due to the number of side effects that was seen after they had acquired swine influenza. Pregnant women also had high complication but if they are treated beforehand then they are safe. Elderly were found to have antibodies to give them some immunity to swine influenza and children were less likely to get swine flu unless they were in contact with people with underlying condition or people with swine flu.


People with underlying conditions are most at risk of H1N1 influenza infections because of underlying medical conditions they were more vulnerable to catch the influenza and get further complications.


Influenza virus is a common human pathogen that has caused serious respiratory illness and death over the past century. It has the potential to cause widespread pandemics. A pandemic occurs when a new type of influenza strain appears in the human population and then spreads easily from person to person.1 Swine influenza has come into the attention with its current occurrence in humans. It has affected a large number of countries globally, indicating that it is capable of causing large scale pandemic destruction. Reports of the widespread transmission of the swine flu (H1N1) virus in humans in Mexico, the United States and elsewhere have out the health authorities to high alert. 2 Swine flu virus, a respiratory virus initially known to cause infection in pigs, belongs to the Orthomyxoviridae family of viruses that include influenza A, influenza B, influenza C and thogotoviruses. 3 Swine flu virus generally circulates throughout the year but the disease mostly occurs during the late fall and early winter season. It has a major economic impact on the swine industry in the United States as it causes high mortality and morbidity in pigs, resulting in financial losses. 4 The most commonly circulating strains of swine flu viruses isolated from pigs in the United States are H1N1, H1N2,H3N2 and H3N1, which belongs to influenza A subtype. 5

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Influenza A viruses are a genus of the family Orthomyxoviridae. They are RNA viruses with a segmented genome that is comprised of eight negative-sence, single stranded RNA segments.6 These eight segments encode eleven proteins. The polumerase complex incluseds the PB2, PB1 and PA proteins as well as the nucleoprotein (NP). There are two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA). Matrix protein 1 (M1) is the structural protein of virus particle while matrix protein 2 (M2) forms an envelope- spanning proton channel. The genome also encodes two non-structural proteins (NS1 and NS2) as well as an alternate reading Frame protein from PB1 known as PB1- F2. 6

The swine flu virus was first implicated as a human pathogen in 1918 when pigs and humans were infected simultaneously. 7 The pandemic virus was transmitted from humans to pigs, and branched off into two lineages; human and porcine, which exist even today. The classical swine influenza lineage has evolved continuously since 1918, while the human lineage has caused many episodes of pandemics and endemics of influenza from 1918 to 1956. 8 The hyman line apparently disappeared entirely around 1957 only to reappear in 1977, and has circulated endemically in humans recently 9 (table 1). The influenza virus was established as a cause of disease in pigs in 1930. 10

In 1970, transmission of the influenza H1N1 virus was reported in the swine population of Asia. 11 A new variant of the H1N1 virus appeared in 1976, which caused the deaths to many US army soldiers, and was found to be A/New Jersey/1976/H1N1. 12 Studies showed that the new strain was closely related to the 1918 pandemic strain. In 1988, appearance of a new triple reassortant swine flu virus H1N1 in Wisconsin killed many persons.13 In 1994; reasserted avian- human H1N2 influenza was isolated for the first time from the UK. 14 Further, between 1997 and 2002, the emergence of new strains (H3N2 and H4N6) was reported as a cause of influenza among pigs in North America 15. Between 1958 and 2005, 37 cases of swine influenza were reported among civilians, out of whom 6 people died and 16 had a history of exposure to pigs 16 (table 1). Since then only 12 cases of human infection with swine influenza virus have been documented.

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On 17 April 2009, CDC reported for the first time that a new strain of swine flu virus had infected two children in California, United States. 17 The recent H1N1 virus strain has been found to be closely related to the swine flu virus but with a genetic composition that is quite different from the earlier known isolates. 18 After that, 5 more cases with the same strain were reported from the United States. At the same time, the public health agency of Canada confirmed 18 cases of respiratory illness in Mexico, with 12 of them being genetically identical to the Californian virus. 19

Following the outbreak, on 2 May 2009, it was observed that there was a clear link of previous swine flu infections in the United States and Mexico. 20

Figure 1.1 Genetic reassortment in influenza virus. 21

As shown in figure 1.1 that reassortment of avian and human influenza virus genes could occur in several ways. One possibility is the direct introduction of an avian virus into humans. The other possibility is that a reassortant is generated in birds after the introduction of a human virus and then transmitted to humans. Alternatively, other species of animals susceptible to both human and avian viruses might serve as intermediate hosts. Pigs are attractive candidates for this role. They can harbour human as well as avian influenza viruses and the nucleoprotein gene of some swine viruses can complement the avian NP gene containing temperature sensitive mutations, whereas that of human viruses cannot. Pigs are involved more frequently in interspecies transmission of influenza A viruses than are other animals.

Genetic analysis suggested that a reassortment event was responsible for the appearance of the novel H1N1 strain of swine influenza originating from two strains, from swine in North America and Eurasia.22 As of 13 April 2009, Mexican authorities had reported around 2000 cases of respiratory illness mainly affecting healthy young adults. The most recent updates given by WHO confirm a total of 2,67,105 reported cases of swine influenza affecting 175 countries, with a total of 2,692 deaths. 23

Aims and objectives:

The main aim of this project is to investigate and analyse what population group is most at risk of developing H1N1 swine influenza compared to other population risk groups.

The following will be addressed in order to determine the risk group most vulnerable to swine influenza:


What is H1N1 swine influenza and what are the different types of viruses

Where does swine influenza originate from and what is its prevalence

What are the signs and symptoms of swine influenza and how is it diagnosed

What are the treatments and preventative methods used for swine influenza

Pregnant women and effects of swine influenza.

Children and the effects of swine influenza

Elderly people and the effects of swine influenza

Patients with other complications affected by swine influenza

The adverse effects of the treatments available

How many patients have been effected in each population group.

Methods & statistical tests.

Secondary data using research papers that have been published regarding this topic had been assessed and the selective information regarding swine flu and the people who are at most risks had been acquired. The information has been utilized to determine the adverse effects of swine flu on certain classes of people.

The data has been collected mainly from published British and American medical journals from internet. They have been analysed to see the compatibility and quality of data with relation to the topic. Online electrical journals will be used from Pub med, EBSCO online and, NHS website and NHS Evidence website.

The published date and time of the journals will be the criteria and the recent journals will be given more preference and journals older than 15 years will not be considered. Only those journals has been used which have been cited more than 10 times the key word used were "H1N1 influenza, swine flu, H1N1 elderly, H1N1 pregnant women, H1N1 children". Only those journals were included which shows the details results and were accessible fully from PubMed. Only the human studies has been included no data has been used from animal. Only the journals which were in English language has been included and the data which is directly related to the topic has only been included as well. The data which is not in English has not been included and those journals which have got limited data were not included and also those which were not for authentic sources are also not included.

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Books are also resourceful for this study as in providing background information on influenza virus and its types, how it affects the body and the general symptoms of swine flu and its adverse effects on people with certain conditions. University library, City Central Library and Bury Town Library will be where many of the published data has been retrieved. The university library catalogue has been used to search for relevant information regarding the topic.

The data that has collected includes people who are at most risk of swine influenza. Data retrieved also includes the causes and symptoms of swine influenza along with prevention measures and treatments.


The question of who is most at risk of H1N1 swine influenza has been addressed here in a comprehensive manner. The population groups of swine flu have been studied to find that all population groups are at risk. But the extent to how much risk they are at has been described below as according to null hypothesis no certain group is at high risk of complications of swine influenza.

There were a good number of papers detailing the potential risk that pregnant women have in terms of complications with swine influenza. The evidence varied however a good amount of quality papers gave valuable information regarding the pregnant women in danger of getting swine flu.

Jamieson et al conducted a study based on 34 women ranging from age 15 to 42 years, in the USA who had got potential symptoms of swine flu. 22 (65%) women were in the first or second trimester of pregnancy and nine (26%) were in the third trimester. Jamieson found that 94% of the pregnant women had influenza-like symptoms such as fever, cough and/or sore throat whereas the symptom onset ranged from April 14 to May 6. (Table 1) Other symptoms were also assessed to find whether the women had acquired swine flu. 24 (Appendix 1)

Table 1:

The number of women with the symptoms.


Number of Women



Sore throat




Table2 : Data are number (%), unless otherwise indicated. *Pregnant women compared with non-pregnant women of reproductive age. †Includes men, non-pregnant women, and children of all ages. ‡Pregnant women compared with all non-pregnant people. p=0·05 for pregnant women compared with non-pregnant women of reproductive age. p=0·05 for pregnant women compared with non-pregnant women of reproductive age; p=0·0005 for pregnant women compared with non-pregnant people. ||Information about myalgias not consistently collected for non-pregnant people because it was only ascertained in an "other, specify" field.

Another study conducted by Jimenez et al in Brazil where the mortality rates for pregnant women were high. The study based on 57 pregnant women who were hospitalised for severe H1N1 influenza. They were aged between 15-41 years, among them 5 (8.8%) were in their first, 22 (38.6%) in second and 30 (52.6%) were in their third trimester of pregnancy. Jimenez el al found that around 13 (22.8%) has comorbidities which includes 3 (23.08%) had asthma, 2 (15.39%) had diabetes mellitus, 2 (15.39%) had HIV, 1 (7.69%) had a cardiovascular disease, and 3(23.08%) had other conditions. Out of 57 patients most of them gave birth at hospitals, the new born babies who were admitted in to the ICU were the ones who were premature none of the new born shows any evidence of swine flu and were healthy. 25

According to Yates et al from NHS foundation trust Newcastle upon Tyne. 90 pregnant women with ILI (Influenza Like Illness) were studied in the research according to the research 55 of them were prescribed antiviral drugs and in 42 (76%) cases this was within 2 days of symptom onset. The comparison had been conducted between pregnant and 1329 uninfected pregnant women who had been offered vaccination; pre-existing asthma was the main maternal factor which is considered as ILI presentation. Other diseases such as obesity and smoking during pregnancy were the major reason for hospital admission with H1N1 infection. According to the study it had been identified that pregnant women in third trimester of pregnancy have been considered at high risk of developing influenza associated pneumonia and cardiorespiratory complications. 26

Study period from 7 September 2009 to 29 January 2010 by the cut-off date of 8 March 2010. These sentinel practices had a combined list size of 216,193 women, including 45,647 who were aged 15-45 and 2431 (1.1%) who were recorded as pregnant as of 1 December 2009. These practices reported 26 consultations involving ILI in pregnant women over the 21 study weeks, giving a mean weekly consultation rate of 51/100,000 amongst pregnant women. As a proportion of all pregnant women, 1.1% (95% CI 0.7% to 1.6%) were reported to have presented with suspected influenza at some point during the study period .26

Launy et al tested 1995 children for novel influenza A (H1N1). The median age was 4.9 (range 0.1- 18 years). 622 were positive where 222 children were hospitalized; 11 were excluded from the analysis because their hospital admission was not directly related to influenza. Data from 202 children were included in the analysis (Figure 1). 27

clinical features of padiatric.JPG

Among these children 59% had underlying medical conditions clinical findings at admission were fever (98%), cough (88%), congestion/rhinorrhea (58%), gastrointestinal symptoms (47%), oxygen saturation below 95%(33%), sore throat (20%), and neurological symptoms (9%). 22 (11%) children were admitted to intensive care unit, and 14 patients needed respiratory support. 27

A nosocomial influenza infection was diagnosed in the other nine patients

(two in the first wave and seven in the second wave); these patients were analysed separately. 27

Among these children, 60 (50%) had respiratory involvement, with asthma being the most frequent (n = 46, 38%). Among children without respiratory conditions, immunosuppression (n = 14, 12%) and sickle cell disease (n = 11, 9%) were the most frequent underlying medical conditions. Encephalopathy (n = 12) was most often associated with chronic respiratory conditions (recurrent aspiration (n = 4) or asthma (n = 4)). The median delay between the first symptoms and initial medical evaluation was 1.5 (range 0-10) days. Thirty-five (28%) children hospitalized during the second wave had received the adjuvanted monovalent vaccine against H1N1. The median delay between vaccination and the occurrence of the first symptoms was 3 (range 2 to 18) days. Three children developed influenza 10 days or more after the vaccination, two of them were immunosuppressed. 27

According to Dayanand el al study a total of 307 children in 2009 with H1N1 influenza infection were hospitalised among them 80 (26%) were admitted to the ICU. The median age of the ICU patients was 6.7 years and of floor patients was 5.7 years. The children who were admitted in ICU were aged between 4-5 years and the largest no of children admitted to the floor was less than 2 years old. 28

203 (65%) children had underlying medical conditions which includes asthma (26%), neurological disorders (24%), and obesity (19%) were the most common. 30 (38%) children were admitted in to ICU who had neurological condition. 44 children (20%) admitted to floor had also had underlying neurological condition.28

Seema Jain et al obtain data of people who were admitted. On admission, 50 of 246 patients who were tested (20%) had leukopenia, 87 of 238 (37%) had anaemia, and 33 of 234 (14%) had thrombocytopenia a (Table 3). 29

Three of 182 patients had positive blood cultures: a 78-year-old man with Escherichia coli urosepsis, a 55-year-old woman with Streptococcus pneumoniae and group A streptococcus infection and a lung-tissue specimen that was positive for S. pneumoniae (as identified by immunohist chemical and molecular assays performed at the CDC), and a 17-year-old boy with pneumonia who had blood and endotracheal-aspirate cultures that were positive for methicillin-resistant Staphylococcus aureus. Bacterial infections that were identified from sources aside from blood samples included group A streptococcus, which was identified by means of immunohistochemical and molecular assays performed at the CDC, in a pleural-biopsy specimen from a 23-month-old boy with pleural empyema, and S. pneumoniae in two patients: a 57-year-old woman with pneumonia who had a positive urinary antigen test and a 58-year-old woman with pneumonia who had a positive culture obtained from bronchoalveolar-lavage fluid. 29

Of the 249 patients who underwent chest radiography on admission, 100 (40%) had findings that were consistent with pneumonia; the median age of these patients was 27 years (range, 1 month to 86 years), and 66% had an underlying medical condition. Radiographic findings included bilateral infiltrates (in 66 patients), an infiltrate limited to one lobe (in 26), and multilobar infiltrates limited to one lung (in 6); data were not available for 2 patients. 29

Shlomai et al tested 179 patients who were admitted to hospitals in Tel Aviv for the presence of S-OIV (swine-originated influenza virus. Treatment with oseltamivir was initiated in almost all patients, but only 65 of the 179 (36%) were ultimately found to be positive for pandemic (H1N1) 2009 infection. 30

As shown in Table 1, H1N1 virus-positive patients tended to be younger with significantly less comorbidity, as compared to negative patients. In addition, typical signs and symptoms of flu-like illness such as fever, cough and myalgia were significantly more common among H1N1-positive patients [Table 1]. However, no significant difference in major laboratory values, except for a slight rise in the level of creatine kinase was detected between the virus-positive and negative patients [Table 1]. 30

Multivariable logistic regression identified two variables as important independent predictors of H1N1 positivity: age younger than 65 (odds ratio 12.5, P < 0.0001) and the presence of cough (OR 5.9, P < 0.0001). The model had an area under the ROC curve of 0.81, suggesting a very good prediction.

Interestingly, the mean time from admission to the first sampling for the presence of pandemic (H1N1) 2009 virus was significantly shorter among the virus-positive patients, reflecting the much higher percentage of patients among the positive patients for whom a H1N1 virus sample was taken on admission: 77% in the virus-positive group versus 57% in the negative group. 30

Bandaranayake et al collected 1687 serum samples and individual risk factor data between November 2009 and March 2010, three months after the end of the 2009 H1N1 wave in New Zealand. Participants were randomly selected from general practices countrywide and a written informed consent was obtained from all participants. The immunity levels were measured in the participants and the results from these samples showed the immunity acquired during the first wave from April to September 2009 as well as any pre-existing immunity. This was done by measuring neutralising antibodies to 2009 H1N1 using pre-pandemic (baseline) and post-pandemic serum samples. The risk factors for 2009 H1N1 were also analysed by using information collected from questionnaires which were given to the participants which included the participant's demographics, history of influenza-like illness (ILI) and other acute illnesses along with vaccination history and living conditions .31

A 5ml blood sample also collected and transported to WHO National Influenza Centre (NIC) at Institute of Environmental Science and Research (ESR) for haemmagglutination inhibition testing. The antibody level was measured as the titre of heamagglutination inhibition A total of 1147 participants were used to detect antibodies against 2009 H1N1. 31


Jamieson DJ et al study which was carried out on 57 pregnant women who were hospitalised with H1N1 virus in Brazil, 14% were admitted to the ICU and there were no maternal deaths associated. According to Louie JK et al and Lim ML et al study the hospital admission for pregnant women ranges from 22% to 25%. Louie JK et al also reported in their study that only hospitalised pregnant women reported 22% of ICU admission and a mortality rate of 8%. The main differences between the study conducted by Louie Jk et al and Lim ML et al and the study by Jimenez et al were the rates or patients who received antiviral treatment and the rates of patients whose antiviral treatment was promptly initiated. Thus according to Jimenez et al study the results seemed to be mainly related to prompt administration of antiviral drugs to the patients who received clinical diagnosis of influenza A H1N1. 24

Jamieson DJ et al and Louie JK et al found that it is during the third trimester of pregnancy when swine influenza virus can be attained; however in the study the severity of the influenza was not related to advanced pregnancy. On the other hand there were only a small number of patients in the first trimester in the study which limited the observation and comparison between trimesters. Louie JK et al also compared the pregnant and non-pregnant women who had H1V1 and Jimenez et al compared the pregnant women with H1V1 infection with or without comorbidities. Using the logistic regression it can be seen by Jimenez et al that there was no increase in the rates of ICU admissions even while controlling for pregnancy duration at the time of infection. The only reason which Louie JK found was the age difference i.e. the pregnant women are on average younger than non-pregnant women and those who had comorbidities were not severe. Also during the other pandemics of influenza, previously healthy young people have been severely affected by the 2009 H1N1 influenza. 24

The short coming of Jamieson et al study is that some patients included without laboratory confirmation of diseases. Only 27 patients 47.37% could obtain RT-PCR testing's, among 27 only 19 70.37% of the patients who were tested by RT-PCR for H1N1 influenza were positive. 24

The finding shows that the pregnant women can be in serious complications but the chances of mortality are very less according to Jamieson et al the influenza viruses can cause serious illness in healthy pregnant women, the empirical antiviral treatment should be promptly started not only for those who were in the third trimester has been considered at most risks of H1N1 influenza complication but those who are in the first trimester of and had no comorbidities should also be promptly tested and treated, Jamieson et al suggested that the mortality will be greatly reduced if parental care is provided in time and all pregnant women are informed about the importance of vaccination .24

Jamieson et al and Dodds et al found that the prevalence in pregnancy7% is higher than the normal public 1% and in past pregnant women were at risks on influenza associated morbidity and mortality. 24

However, Libster R et al, Neuzil et al and Lister P et al conducted a study on children of less than 2 years of age which had been considered at high risk for hospitalisation with seasonal and H1N1 influenza infection and also they were considered to be at high risk of admission at the hospitals 32 but according to Daynanad et al study they contradicted these findings and according to them the older hospitalised children with H1N1 influenza were at high risks of requiring ICU treatment than the children less than 2 years old. 28 According to Dayanand el al the age group 4-5 years were found to be at high risks of severe 2009 infection and the median age was 6 years which as compared to 2008-2009 influenza seasons where the median patient ages was 1.8 years which is highly significant. 28

Dayanand et al stressed that the main reason for the peak age difference in disease severity of H1N1 are not clear. The only possibility that could explain this would be that the younger children don't have robust immune response to H1N1 influenza so therefore they don't develop severe pulmonary disease which may be immune mediate. This could result that the 2009 H1N1 virus elicits different robust immune response than seasonal influenza. However in the past it was considered that younger children were targeted for early treatment . The study conducted by Dayanand rejected the hypothesis because 85% children aged 2 and less than 2 year old received oseltamivir within 24 hours of admission and there were no significant differences between the times of onset of illness to admission between these groups. Alternatively when the Denver public school opened after holidays after 6 weeks of reopening the epidemic peak resulted in larger number of school children infected some of whom developed severe infection .28

According to Amir Shlomai et al who carried out a study of hospitalised patients during 2 month period with flu- like syndrome based on demographic, clinical and laboratory results found that among hospitalized patients suspected of having H1N1 infection, those found to be positive for the virus tend to be younger and have significantly fewer comorbidities as compared to those who are negative. 29 Secondly, Amir Shlomai et al found that the typical symptoms and signs of influenza, including fever, cough and myalgia, are more common among pandemic (H1N1) 2009 virus-positive patients. Thus, supported by a multivariable logistic regression analysis of data, Amir Shlomai et al conclude that younger age and the presence of cough on presentation are two parameters that may predict H1N1 positivity among hospitalized patients with a flu-like illness. 30

Itoh Yet, Shinya K, et al, Perez-Padilla R et al, Jain S, Louie JK et al and Michaelis M et al found that this observation joins a growing body of evidence indicating that the novel pandemic (H1N1) 2009 virus tends to cause complications in relatively young people who were traditionally thought to be at a low risk for flu-related complications. 33

Ikonen N et al suggests that the younger age of the severely infected patients may be due to the presence of cross-reacting protective antibodies found in older individuals who have been exposed to the Spanish flu virus. These antibodies cross-react with the present pandemic (H1N1) 2009 virus, providing the elderly population a relative protection from the present epidemic .34

However Dayanand et al found that the main cause of admission to ICU were the underlying neurological disorders , on the other hand half of those who had underlying neurological disorder didn't have any associated neuromuscular or pulmonary disorders such as asthma, chronic aspiration or recurrent pneumonia. These results proved that this group needs an urgent attention and need to be targeted for immunization, prophylaxis and early diagnosis tests and prompt treatment as they had underlying disease. 28 This was also seen by Hancock K, et al Cate TR et al and Dol R et al who conducted a study based on children with underlying diseases. They found that children are more likely to be exposed in schools so the youngsters have more susceptibility to the virus as compared to 60 year old or more, hence young febrile are more likely to be diagnosed as older people with influenza mostly don't have fever. 31

It can also be seen from the study that 2009 H1N1 A hospitalised children and older age with underlying medical condition were significantly at high risks of complications and admission to ICU. These observations identify that increases emphasis on diagnosis, prevention and new treatment should be done in future for H1N1 infections. 31

According to Seema Jain et al study of patients from USA who were admitted in hospitals with H1N1 influenza infection in 2009 during the first two months of pandemic. The pandemic caused severe illness such as pneumonia and ARDS which resulted in ICU admissions. Seema Jain et al found that underlying conditions were among 272 patients according to Thompson WW et al study it was noted that during the seasonal influenza most of the hospitalised admission were among persons 65 years or older and those under the age of 5 years. Seema Jain et al study found that nearly half of the patients who were hospitalised were under the age of 18 years and more than one third of the patients were aged 18 - 49 years old and 5% were aged 65 year or older. 29

Seema et al carried out a study on patients who had a high prevalence of underlying medical conditions 73%. Seema Jain et al found that 82 % of the patients were considered to be high risk of influenza related complications on the bases of age which is between less than 5 year old to up to 65 year old or more or the presence of underlying medical condition . 29 According to Schrag sj et al, Keren R et al and Ampofo K et al the proportion of children 60% who had underlying conditions was higher than those children 31 - 43%who had been reported and hospitalised with season influenza . Walsh EE et al , Neuzil KM et al and McGeer A et al the data published by CDC 44-84% of adults admitted to hospitals with seasonal influenza had underlying conditions which according to Seema Jain et al study 84% hospitalised adult patients had underlying medical conditions. 29

According to Hancock K, et al Cate TR et al and Dol R et al asthma and COPD (chronic obstructive pulmonary disease) were the most common underlying medical conditions found in patients and only few of the patients had neurocognitive and neuromuscular disorders on the other hand Hancock K, et al Cate TR et al and Dol R et al found that children were disproportionately affected by these underlying condition and were at higher risks of severe influenza related illnesses. 31

Seema Jain et al were only able to collect height and weights of only 70% of patients out of them 45% were obese or morbidly obese. Seema Jain et al study found that most of these patients 81% had underlying conditions which is associated with influenza related complications. Ogden et al found that the number of people who were obese in US 27% adult population is similar to the one studied by Seema Jain et al 26%. Seema Jain et al study found that the obesity has not been linked to influenza related complications and further investigation is warranted. 29

Finelli L et al found that there were few bacterial coinfections detected although the bacterial diagnostics tests were not performed in all patients, most of the patients were given antibiotics at the time of culture collection. According to FInelli L et al the data collected from paediatric mortality associated with influenza in the USA have shown an increase in the rate of bacterial coinfection which is between 6 to 24% in 2004-2005 and 2006 - 2007 subsequently. Most of these infections are caused by methicillin- resistant S.aures, although these trends were not clear in 2009 H1N1 influenza.

According to Seema Jain et al, only 73% patients with radiographic evidence of pneumonia received antiviral drugs, whereas 97% received antibiotics. Seema Jain et al study suggests that the use of antiviral drugs is beneficial especially when it has been administered early, since the patients who died or admitted to ICU were less likely to have received such therapy within 48 hours after the onset of symptoms. Despite there were limited data available to Seema Jain et al regarding the clinical effectiveness and treatment of antiviral drugs, the treatment should have been initiated to people who were either hospitalised with H1N1 infections, even if the therapy is initiated more than 48 hours after the onset of symptoms, especially with patients with underlying medical conditions such as pneumonia and those with risk of complications such as pregnant women. 29

Seema Jain et al study had limitations such as the patients evaluated represented 25% of total hospitalisations in 2009 H1N1 infection which had been reported to CDC during the surveillance time which ended in June 9,2009, who represented the most of the states that had substantial influenza outbreaks. Most of the participants were volunteered and therefore subject to bias. All diagnostic testing were clinically driven to excellent standard and the data collection forms were all standardised but not all information was collected from patients. 29

Szyper-Kravitz M et al and Tumpey TM et al found that a significant number of infected patients were prone to severe complications and respiratory failure that necessitated an urgent transfer to the intensive care unit. These patients were distinctive for the presence of increased inflammatory markers. This observation may correlate with immune system over-reaction to the viral infection, leading to the so-called cytokine storm, which triggers inflammation and lung damage that can lead to multiple organ failure and death. 35

Monto AS et al found that in contrast to the typical seasonal flu that tends to complications in older and debilitated patients the severely ill H1N1-infected patients were neither older nor previously sicker than the H1N1-infected patients with a milder clinical course. 35

Jain S, et al, Kumar A et al and Louie JK et al study in contrast to above suggesting a severe clinical course in patients with at least one significant comorbidity, the patients with a severe clinical course in Amir Shlomai et al study had no more comorbidities than patients with a non-severe clinical course. However, the three cases of deaths had significant comorbidities (one patient after bone marrow transplantation, one with metastatic colon cancer and one with a history of alcohol abuse and intravenous drug use) that apparently led to the fatal outcome. 35

Bandaranayake el al carried out a study based on 1687 serum samples where serum samples were collected from random patients from General Practices and separated by age and ethnicity which had been obtained between November 2009 to March 2010. The study involved both the community and healthcare workers which consisted of cross sectional design and questionnaire assessing demographics and potential risk factors. 31

The data has been obtained from 1147 76% participants out of 1156. Nine participants didn't respond to questionnaire and thus had been excluded from analysis. 31

The samples were collected from all humans and then treated with receptor destroying enzyme (Vibrio Cholera Neuraminidase) and to inactivate the nonspecific inhibitors of viral haemagglutination the guinea pig erythrocytes had been used. The antibody level was calculated as the titre of Heamagglutination inhibition. 31

Bandaranayake el al found that susceptibility to influenza virus infection is inversely related to the initial titre of serum HI antibody. Hobson D et al Potter CW et al de Jong JC et al Potter CW et al found that the HI antibody titre of 1:40 are correlated with 50% reduction of the risk of contracting disease or influenza infection. The HI titre of 1:40 has been used by Bandaranayake el al and has been used as threshold of seroprotection as well as seropositivity. The proportion of individuals with HI titres of 1:40 against 2009 H1N1 in the serosurvey is referred to as seroprevalenve. 31

Rao Scott Chi - square test which was the modified form of Pearson chi- square test had been used to test the significance of the estimate i.e. p = 0.05. 31

The hypothesis tested for this analysis was to identify the age group or ethnicity were the factors for the likelihood of 2009 H1N1 immunity. The finalised model included variables such as age group, ethnic gropu,sex, vaccination history, chronic illness, reported damp housing, with 2009 H1N1 seroprotective result as the main outcome. 31

The comparison had been done for the proportion of HI titre of 1:40 of individual and between the baseline serosurvey samples of different age groups. According to age and ethnicity standardisation of the national population, almost 18.3% New Zealanders were infected with 2009 H1N1.Lopez L et al and Baker MG et al found that the population cumulative incidence estimates 781,867 cases that were substantially higher than the case estimated from various clinical surveillance data. 31

This can also be seen by a study carried out by Hancock et al who analysed stored-serum samples from trials of seasonal trivalent inactivated vaccines predating the 2009 pandemic and revealed the presence of cross-reactive antibodies to 2009 H1N1 in adults and very little response in children antibody responses to the 2009 pandemic H1N1 influenza virus showing that the elderly are less at risk of swine flu than the children. 31

On the other hand the people who were not vaccinated those who were vaccinated respond with higher HI titres when infected with pandemic virus because they had been primed with seasonal influenza vaccination. Secondly, the individuals who had seasonal influenza vaccination may have had an increased risk of contracting H1N1 as compared to those who were not vaccinated. This would result in higher titre HI levels as compared to those who were not vaccinated. 31


Many studies have been carried out based on different groups with swine flu. However from the research carried it could be seen that there was not enough data or research carried out which was based on all target groups. Therefore this study is based upon all target groups such as children, the elderly, pregnant women and patients with underlying medical conditions in order to compare and find which target group is most at risk.

The aim of the study was to find which target group among the four were at high risk of attaining swine influenza and getting complications. This has been done by determining the influenza-like symptoms shown in patients after they had caught swine influenza, the number of symptoms shown and the severity at which they had evolved and how quickly they affected the rest of the target population along with the outcomes of all the groups after getting the swine influenza

It can be seen that the elderly over 65 years are less at risks of swine influenza due to possible earlier antibodies and immunity (think of better way of saying dis bit). There was very less no of pregnant women who actually died due to swine influenza and however studies shows that if precautions are taken in time and they were treated in time then there are less chances of pregnant women to get in to complications due to swine influenza infection however the people with underlying medical conditions shows constant complications of swine influenza infections which makes them more at risk of swine influenza.

It was revealed that patients with underlying conditions are at most risk of swine influenza because it is not the swine influenza that actually is responsible of complexities in this group it was the underlying conditions which triggers the infections and causes more severe destructions compared to all other groups.

The data which I found out was very limited as x, more research need to be done and people need to be informed in more details about the actual facts of swine influenza and those who were considered at high risks should be identified and diagnosed at early stages so that proper treatment can be given in time.

So from the results and discussion it was concluded that the people who had underlying medical conditions irrespective of age, sex or ethnicity they are vulnerable to increased risks of having complications or getting the influenza H1N1 infections , but as for hypothesis no body is at risk of getting in to extreme conditions after getting the swine flu as from the data it has been seen that the no of people who actually died of swine influenza as compared to total no of people who were infected were very less so it has been proved and the aim has been achieved that there are people who can get in to complications especially those with underlying conditions but null hypothesis has also been proved that nobody is at high risk of getting in to complications.