Investigation Of Influenza A H1n1 Epidemiology Biology Essay

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Due to the recent patterns of its spread amongst humans, Influenza H1N1 commonly called swine flu, raised concerns of organizations like the World Health Organization (WHO) and has resulted in investigating into the controls and vaccinations that can be used to prevent and reduce morbidity rates that are a result of the spread of swine flu. In this paper will review the epidemiology of swine flu an also discuss whether or not vaccinations are the best prevention strategies for this disease in light of the many control measures that are available to the population like facemasks, N95 respirators, hygiene, etc. The paper will also highlight how the improvements in the surveillance and control measures have influenced the management of this pandemic.


Influenza is an acute respiratory disease caused by influenza viruses, known to be one of the most common cause of infectious disease in humans (Zimmer and Burke, 2009) and responsible for serious respiratory illness and deaths over the past 100 years (Khanna et al., 2009).

Because of its ability to constantly adapt through antigenic drifts and shifts respectively, influenza viruses often result in epidemics (e.g. seasonal influenza caused by influenza B viruses) or pandemics (e.g. swine flu caused by Influenza A/H1N1 virus) (WHO, 2009).

Influenza pandemics occur when a new strain of influenza A virus, that has never circulated in humans before, appears and to which the population has very little or no immunity against it (WHO 2009). Therefore, it causes serious illness and spreads easily from person to person as most people are susceptible.

Since mid March/April 2009, a new influenza A/H1N1 virus has been identified first in Mexico and the USA and then has spread rapidly across the globe (Fraser et al., 2009). On June 11, 2009, by the time the World Health Organization (WHO) had declared swine flu as pandemic, 74 countries and territories had confirmed laboratory infections. As of 28 February 2010, more than 213 countries reported laboratory confirmed cases of pandemic influenza H1N1 2009, including at least 16455 deaths worldwide (WHO, 2009).

Last century, 3 flu pandemics (1918, 1957 and 1968) took place with millions of deaths all around the world as a consequence (Kiely et al., 2009). Influenza pandemics are events that occur from time to time and are for that reason a permanent threat to humans. Even though this new influenza A/H1N1 virus has been proved to be relatively mild, because all viruses can mutate and become more potent, to stop the spread of the virus is a public health priority (Bronze and Wolf, 2010).

To understand how influenza H1N1 is transmitted and why it is causing illness and deaths in humans, it is important to review its aetiology and investigate its epidemiology. This will allow a better understanding of the disease, take action against the pandemic and deal with the transmission and control of influenza H1N1.

Also, as preparedness is crucial in order to respond to future influenza outbreaks, it is essential to critically evaluate the different control measures (facemasks, school closure and mass gatherings, hygiene and education) developed against this pandemic and its evolution to the release of the vaccine.

Background history

Swine flu is a highly contagious respiratory disease caused by influenza A viruses, which usually occur in pigs. Direct transmission to humans is rare; however, the swine influenza virus can be transmitted to humans via contact with infected pigs as they are candidate for genetic reassortment (between avian, swine and humans flu viruses) and/or contaminated environments (CDC, H1N1 flu).

In 1918, the first influenza A/H1N1 pandemic associated with a virus of swine flu origin, implicated as a human pathogen, reported about 500 millions of cases worldwide and approximately 20 to 50 million deaths (WHO, 2009).

At the time of Spanish influenza (1918 pandemic), scientist did not have an idea of what was causing the disease, there were no vaccines nor any treatments such as antivirals against the virus and the intensive care facilities were very restricted. The cause of human influenza and its links to avian and swine influenza was not understood. It was only in 1930 that the virus has been isolated from swine and humans.

1918 influenza pandemic was more lethal than seasonal flu and the mortality rate was also unusually high in young strong healthy people.

The 1918 pandemic was not the only isolated event of the 20th century, the 1957 pandemic (Asian flu H2N2) with 2 millions of deaths and the 1968 pandemic (Hong Kong H3N2) with 1 million of deaths (Zimmer and Burke, 2009). Because influenza pandemics introduced the emergence of a completely new strain of influenza A virus, the population is left with no immunity and the virus spread very quickly. Therefore, influenza outbreaks should not be taken lightly as it can kill millions and mitigating its effect is a public health priority (Fraser et al., 2009).

Current H1N1 pandemic

On June 11, 2009, due the spread of the virus and not to the severity of the disease, the WHO declared that a new influenza A/H1N1 pandemic was underway with more than 70 countries reporting cases of new influenza A (H1N1) infection and outbreaks of influenza H1N1 in multiple parts of the world. The virus is transmitted easily from person to person via droplets and small particles produced when infected people cough or sneeze or by touching infected surfaces (Vaque Rafart et al., 2009).

Swine flu is relatively mild. Usually most infected people recover within one to two weeks without requiring intensive medical treatment. Swine flu is characterized by flu like symptoms with sudden onset of high fever, aching muscles, headache, severe malaise, fatigue and sometimes diarrhoea and vomiting. However, in the very young, the elderly, pregnant women and those with other serious medical conditions, infection can lead to severe complications of the underlying condition, pneumonia and/or even death. Treatment with antivirals such are Tamiflu and Relenza which act as neuraminidase inhibitors, is available but most people are encouraged to stay at home for a week and until 24hours after the symptoms have resolved (NHS, conditions on pandemic flu).

Influenza H1N1 morbidity is high but mortality rates are low 1%-4% (GAR, 2009). However protect the susceptible in our population is still a necessity.

Control measures

It is common knowledge that vaccination is the best way to fight against infectious diseases. However, at the time the pandemic was declared, no vaccine was yet available. Therefore in order to reduce the impact of swine flu pandemic, reinforce healthcare and public health measures and education was essential in order to delay the spread of infection. Some examples of these are:

Use of facemask and N95 respirators in the Healthcare/hospital setting

In the healthcare, where hygiene and precaution are part of their daily actions (special clothes, protective glasses, gloves etc.) as workers are exposed to patients with serious chronic conditions, it is important that they could protect themselves and patients who are at higher risk of complications from people infected with the H1N1 virus and avoid further contamination (Hajjar et al., 2009).

The use of facemask is useful in protecting the individual's respiratory system from large particles and large droplets however it won't be always able to filter and block the smaller particles in the air because it is a loosely covering of the face. These smaller particles are mainly air droplets and include germs that can be transferred from coughs or sneezes or different medical processes. An N95 respirator on the other hand has a very close-fit to the face and can block smaller particles as well. Furthermore it also helps filter whatever smaller particles the individual could inhale form the surrounding air. However, for the N95 respirator to function properly, it has to be a perfect close-fitting to the face as any gaps will allow air particles to pass through unfiltered (U.S. Department of Health and Human Services, 2009).

Public health measures

The outbreak of the swine flu pandemic in some countries (e.g. Australia) resulted in the initiation and maintenance of shut downs of school and strict quarantining in order to restrict and contain the pandemic spread. However, school closure is socially disruptive as it obliged carers to take time off work and children's education stopped. Hence, children are at the same risk of getting infected outside their schools as the pandemic is widespread, so that arguments for its effectiveness have not been proved. Total school closure is not necessary but class closure might be considered (WER, 2009). Furthermore, many of the sports and entertainment events were postponed or cancelled (e.g. Mexico in May 2009). This line of action was thought necessary as the percentages of the swine flu cases was expected to increase due to the winter season being near. But social distancing and restrictions on mass gatherings had not been instituted by the WHO as people could also be very easily infected in closed areas (public transport etc.) as well if care wasn't taken (WER, 2009).

Public education

Instead Governments guidelines were to give the population accurate information on the pandemic situation and provide tips on how to prevent spread and individuals from getting infected. In the UK, the National Health Service sent out leaflets and notifications to every household about general facts about swine flu, precautions that need to be taken if and when symptoms are detected at home or in the office to slow down rate of infection and advices on how not to get infected (Hajjar et al., 2009)

Different means were used such as posters and signs, adverts, video clips, and short animated films for children etc. in order to reach and educate the whole population (e.g. videos on on the simple activities that can be hammered onto everyone's daily lives (HPA, swine flu).

This includes:

Avoid close contact with sick infected

Cover nose and mouth with a tissue when cough or sneeze and bin it

Regular hand washing with soap and water or alcohol-based solutions

Stay at home if sick for 7 days and until 24 hours once symptom free

Improved hygiene in workplace and household


When all these measures helped to slow down the pandemic, it did not eradicate the virus and stop its spread.

In late October 2009, the 2009 influenza A/H1N1 vaccine was released and made first available to the at risk group for complications from H1N1 infection and later to the rest of the population (NHS, Information on swine flu vaccine).

Vaccination is known to be the best way to fight viral infection as it will prevent people to get infected in the 1st place and enable to achieve herd immunity. It will not only prevent an individual from getting sick but avoid him to spread the virus to someone else. However, only a very small part of the population is a getting the vaccine (Franco-Paredes et al., 2009)

Despite all these facts, a decline in influenza H1N1 pandemic activity is now being observed. Is this the reason why vaccination uptake is low? Is vaccination still necessary against this H1N1 pandemic? What could be the consequences of vaccination low uptake?

In order to explore the public perception on swine flu and vaccination uptake, the student decided to conduct an online questionnaire.

Questionnaire Methodology


244 respondents among university students and staff, graduates, and families in Kingston, were asked to complete an online questionnaire in order to assess their level of information and perception about swine flu pandemic and vaccine.


This questionnaire comprised a set of closed, open-ended and multiple choice format questions and consisted of 18 questions.

In the first part of the questionnaire, respondents were asked to give their age, gender and occupation. These are important factors to be considered as they will drive some of their answers, opinions and might explain some of the decisions they made and will not be a true reflection of the population… Therefore need these factors are essential to acknowledge any possible biases or irregularities resulting from gender, age, educational level, and etc. if applicable.

The 2nd part of the questionnaire consisted of generic questions about swine in order to assess their level of information (what is swine flu? What are the signs and symptoms? Are you aware of the different treatment available? If yes name them. How can you prevent yourself from getting infected and avoid the spread to others?

In the 3nd part of the questionnaire, participants were asked whether or not they have been vaccinated and to give a reason for their answers and if they agree that vaccination was the best way to fight the pandemic (best prevention), and if they fought that vaccination was still necessary as pandemic activity is low.

For the 2nd and 3rd part of the questionnaire, respondents were asked to give their source of information.


The online questionnaire had a response rate of 20.49% (n=50). The participants are composed of 68% (n=34) students or new graduates with 41.17% of the students in medical related studies (n=14); and non students 32% (n=16) with 25% of them (n=4) working in medical related field.

66% of the population (n=33) was in the 18-24 age group, 30% (n=15) in the 25-34 age group and 4% (n=2) in the 45-59 age group; and72% (n=36) are females against 28% (n=14) males.

All participants confirmed that they have heard about influenza H1N1 and 90% (n=45) of them were able to give a brief explanation of the pandemic, signs and symptoms of the disease. 72% (n=36) were aware of the different treatments available especially Tamiflu and advices in staying at home in the case they were infected.

All participants were able to cite at least one way of preventing themselves from getting the virus and avoid further spread. All participants were aware of the importance of personal hygiene when coughing or sneezing, the use of hand alcohol gels and did mention "Catch it, Bin it, kill it" several times. Only 26% (n=13) mentioned vaccination and 14% (n=7) did mention school closure, mass gatherings restriction and quarantine.

8% (n=4) said that they had no information about the new H1N1 vaccine. 30% (n=15) stated that they had insufficient information. 50% (n=25) affirmed that they have sufficient information about the H1N1 vaccine and 12% (n=6) said that they had a very good level of information on pandemic influenza A/H1N1 vaccine.

However, only 14% (n=7) of the participants have been vaccinated, due to existing underlying conditions, working in the healthcare or being exposed to susceptible such as children.

The 86% (n=43) of non vaccinated participants only 12.2% (n=5) are considering vaccination in the future. The reasons for the 87.8% (n=36) of the participants for not considering vaccination in the future are:

33% (n=17) do not consider themselves at risk of serious illness

21.6% (n=11) do not consider this pandemic as a threat as its activity has declined

13.7% (n=7) have fears about the vaccine safety

13.7% (n=7) have other reasons. They already had swine flu or did not decide yet.

9.8% (n=5) would rather get infected and use alternative drugs as the pandemic is relatively mild and only causes influenza like illness

7.8% (n=4) do not have time

60% (n=30) of the participants got their information on swine flu and vaccine from the media and internet resources.

48% (n= 24) only think that now that pandemic activity is low, the vaccine is not necessary anymore.

42% (n=21)stated that the virus responsible for this H1N1 pandemic is still out there and that vaccination should continue only for those at risk of getting serious complication.

10% (n=5) said that it was absolutely crucial as it is the only way to stop the pandemic


The results from the questionnaire shows that most of the population is not getting vaccinated as they believe that due to the mild behaviour of the pandemic, they are not at risk of serious illness, and now that pandemic is dying off. Despite their good level of information on influenza H1N1, they lack to understand that vaccination is not about protecting themselves alone but the whole population especially the ones who are susceptible. It is correct that most of them are not at serious risk of complications and therefore getting infected will not have serious health issues as the disease is self limited, but they would infect others and contribute to the spread of the disease instead of stopping it. Low vaccination uptake in infectious disease could be lead to the re-emergence of the virus (e.g. measles and MMR vaccine)

The current low uptake of the MMR vaccine in some parts of the UK has raised concerns about the return of measles outbreak among primary school children entrants (The health boards executive, MMR vaccine discussion pack). This was due to the negative media coverage about the vaccine. These concerns contributed to a decrease in the uptake of the MMR vaccine and the re-emergence of the disease in the population with children developing complications such as meningitis, pneumonia, etc. (Euro surveillance, 1999 and HPA) when this could have been avoided.


2009 Influenza H1N1 pandemic has not been deadly as primarily thought and was relatively mild compared to the previous pandemics. Even though the pandemic did not cause millions of deaths, the pandemic response was still appropriate as it was first difficult to evaluate the virulence and impact of the virus on the population. The government preparedness to the pandemic was greater than of 1918 pandemic for example, showing a better understanding and management of the disease. However, the reason for a smooth management of this pandemic is mostly due to the fact that the virus was only causing very mild disease unlike H5N1 otherwise the scenario would have been completely different and the stress for vaccine production would have been greater. This pandemic was an opportunity to educate the public about influenza epidemics and pandemic, simple precautions to avoid contamination and spread, and also helped to increase the intake of seasonal influenza. However, vaccination low uptake could be a major concern for future outbreaks as it might be that people do not understand the primary reason and benefit of immunisation which is to reach herd immunity.


Further studies need to be done in order to find the reason for low vaccination uptake and the communication between the governments and the media about vaccine safety need to be improved.

The production of a vaccine against influenza A viruses need to be quickened in order to respond more rapidly to future influenza outbreaks and therefore diagnosis and isolation of the virus strain should be improved.