Pathogenesis Of Measles Virus Infection Biology Essay

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Measles is a virus called by a virus of genus Morbilivirus, It is an infectious virus which has humans as a primary host, but can infect certain primates. The Measles are highly contagious and self limiting; it is a typical disease of children 1. In developed countries, there is a low mortality rate associated with measles but complications do arise in a few occasions, ranging from things such as mild diarrhoea to pneumonia 2. In immunocompromised patients, such as sufferers of AID's, the mortality rate can rise, especially in undeveloped areas such as sub-Saharan Africa 3.

The highly infectious nature of measles causes occasional outbreaks yearly, but this is normally contained by the use of the MMR vaccine and boosters given to children 4. When a host is infected with the virus, it will attach itself to cells in the host's respiratory system and fuse with its cell membrane. The measles virus has a Negative strand of RNA which allows it to form proteins via the cells own replication machinery, It will then replicate its self using the host cells resources and new viral cells will "bud" off the host cell 5.

Measles is a disease that has potential to be eliminated throughout the world with a proper vaccination program 6, but this is not been possible currently due to issues with apparent risks linked with the vaccination for measles, certain cultures and groups that refuse to be vaccinated on religious grounds and because of the massive cost to complete such a large goal.

.Infection and spread

Measles, as stated above, Is a very contagious viral condition, which infects 90% of people exposed to the virus who have not been 7. It is spread though the air via the infected hosts sneezing and coughing and is carried by infected saliva and mucus through the air to the potential target. The virus can also survive on surfaces and in the hands of the hosts from coughing. It then attaches to the target cells and divides in the cells in the back of the throat. The virus will specifically attach to the receptors on the host's cell via H-Glycoprotein and goes on to infect the cell. From here the virus begins to replicate itself when the cell has produced enough neucleo proteins, formed from the RNA strand inside the viral cell, to encapsidate more virus cells. The host cell then allows the viral cells to "bud off" the host cell, allowing the viral cell to appear as "Self" to the host's immune system and continues to infect more cells 5.The virus takes between 10 days to 14 days to incubate and for patients to start showing early symptoms, but it can take longer 2 .The person who has been infected with measles is usually infectious approximately 3 days before the first symptoms arise and for around 5 days after the symptoms arise. The measles virus itself can only survive upon surfaces such as the skin for a few hours before the cells die. To prevent spread, patients should avoid contact with the public and stay at home in bed; this prevents the disease spreading to other people. When required to go out, patient should cough or sneeze into tissues or the elbow to prevent the virus spreading via the air into the general public. Sneezing into the elbow joint instead of the hands also helps stop spread by limiting the number of people that come in contact, as you are more likely to touch something or someone with your hands yet you are unlikely to make much contact with people with your elbows. The demographic at the highest risk of infection from this virus are young children that have not been immunised, generally between the ages of 3 and 5. Other groups that have a high risk to this disease are immunocompromised people, such as those undergoing chemotherapy or infected with AIDs. People that are at low risk are those that have never been vaccinated against it 6.


In measles there are a few common symptoms. The initial symptoms are; a fever which can peak at around 40o C, a runny nose, redness of the eyes and sensitivity to the light. These symptoms tend to occur approximately one week after infection 8. At around 4 days after infection small, white spots start to spread on the inside the patient mouth, these are called Koplik's Spots, But in some cases these are difficult to detect as the can fade 9. This is then followed quickly by a rash, spreading from, typically, behind the ears, across the face then throughout the whole body of the patient. This rash cause's an "itching" sensation on the skin which, if the patient is allowed to scratch could cause scarring. There can also be various other symptoms associated to measles which included: loss of appetite, aches and pains throughout the body, tiredness, lack of energy and a dry cough. All of these symptoms can last for up to around two weeks before they begin to show signs of fading.

There is no treatment currently for Measles and most patients will recover with rest and supportive treatment. Generally patients are given painkillers to easy aches felt by the patient, kept cool but not cold to reduce fevers and given plenty of water to prevent dehydration. There are also currently tests to see if Vitamin A helps with measles, although results have currently shown no reduction in mortality 10.

Measles can usually be identified by a GP from the symptoms, Although Measles can be misdiagnosed based on the initial symptoms and thought to be a number of problems, such as an upper respiratory track infection or influenza and after the characteristic rash forms, it can still be misdiagnosed for other rash inducing illnesses such as Roseola, Chicken pox and German measles. To confirm that it is indeed measles, a lab diagnoses can be carried out and a variety of tests that could be used, such as a simple blood test would be carried out on the sample7 another possible test is an immunoassay test which uses the saliva, which, if the patient is infected should contains measles specific IgA antibodies.

In immunocompromised people, the symptoms progress more quickly and without adequate treatment, cannot recover. Measles can have up to a 30% mortality rate to people afflicted with it and that are currently in immunocompromised states3.


Vaccination, which was discovered and attributed to Edward Jenner, is the process of introducing a foreign body into the body either in parts or in an attenuated form. When the person comes into contact with the foreign body, the body recognises the substance as "non-self" and beings to remove the foreign body by a large number of methods. When the foreign bodies have been completely destroyed, B cells differentiate into B memory cells, which will "remember" the specific body. If the same thing invades the body again, the B memory cell is able to proliferate much faster allowing the foreign body to be destroyed much faster.

In term of infectious diseases, this process of immunization allows the body to mount a much faster response, prevent the disease to propagate as fast and destroys it before there is much chance for it to cause any symptoms. Vaccination can be done in different forms, either injection of an inactivated form which cannot reproduce and is not infectious but requires occasional booster shots or in an attenuated form, where live bacteria or virus' are injected in a less virulent form, which does not require occasional boosters although there is the possibility that the disease can spread in the body of immunocompromised people causing illness.

Measles is a recurrent infectious disease which has been responsible for many deaths worldwide. Outbreaks in Central America in places such as Honduras, Mexico and Cuba in the 1500's killed many people and, in the last 150 years it has killed approximately 200 million people 11. But in 1954, the disease was isolated and from 1963 licensed vaccines became available 12.

The MMR vaccination, which is the UK's major vaccination against measles is usually given to children which are around the age of thirteen months and then a booster vaccine is given to them between the ages of three and five years old when they start schooling. There have been recent controversies though, with the MMR vaccination in Britain due to claims that there is a risk of autism in children that have been vaccinated. These issues were raised in "The Lancet" in 1998, which is a medical journal produced in Britain 13. But when it was researched, it was shown that there was no reliable evidence that there was a link. But due to scepticism in the public, many prevented their children from receiving the vaccination. This had major setbacks as there was a mass outbreak of measles, mumps and rubella with approximately 1000 new cases in 2007 which was "the largest amount since records had began" 14. There are similar problems about vaccination in Nigeria because of religious beliefs; people do not want their children vaccinated. Although the process of vaccination is not perfect, it is the best defence against measles and, like smallpox before it has the potential to be eliminated and five of the six regions who are included in the World Health Organisation, "WHO" believe that it could be eliminated by a series of vaccination and could be reduced by up to 95% by the year 20156.

In itself, measles is not a particular deadly disease with less than 0.2% of cases resulting in death there is still chances of complications which can prove to be fatal. Some of these complications can be mild, such as bronchitis, otitis media and ear infections but some can be major and potentially life threaten such as pneumonia, Acute measles encephalitis, , giant cell pneumonia and subacute sclerosing panencephalitis 15.

.Subacute sclerosing panencephalitis

Subacute sclerosing panencephalitis is a rare complication which arises from measles. It is also known as Dawson Disease and Measles encephalitis. It is causes by the infection of a patient by a strain of the measles which is immune resistant. The disease is a progressive neurological disorder which has no known cure but, with medication it can be controlled although is normally fatal within 1 to 3 years 16.

The early symptoms of SSPE are infection of measles at an early age (1-2 years old) there is then a latent period, in which there are no visible symptoms and

Eventually leads to neurological problems. These signs can be recognised by poor mental performance and problems with concentration. There are also reports of temper outbursts and hallucinations 15.Eventually, the patient will experience muscle spasms and mental retardation, Seizures and possible blindness. In the advanced stages of the disease, the patient will lose most muscle function and progressively deteriorates to vegetative state. The causes of death in these patients can range from suffocation due to the loss of control of muscles or a secondary infection, such as pneumonia 16.

Patients are kept on anticonvulsant drugs and therapy, administration of Interferon and antiviral medication. Although these drugs will not cure the patient, it will help with their quality of life and extend their lifespan slightly. Patients in the final stages of the disease are kept on palliative care.