What you need to know about: Measles

The Persian Physician Rhazes in the 10th Century referred to a disease ‘more dreaded than smallpox’. Measles was indeed a major public health concern with major epidemics occurring every 2-3 years; the discovery of the measles vaccine (1963) and mass vaccination drives which followed meant that approximately 21.1 million deaths were prevented between 2000-2017. In just a few decades, a prolific disease has been reduced to the sidelines, an impressive testament to scientific advances. However with a rising tide of skepticism against the safety of the vaccination the success of the treatment is in danger of being undermined.

Measles is caused by Measles morbillivirus, a virus which only affects humans and is rapidly transmitted through the air when an infected individual coughs or sneezes. Once inhaled, the virus primarily affects the epithelial cells in the trachea. Hemagglutinin ( H-protein) on the virus’ lipid envelope membrane binds to receptors on the epithelial cell’s membrane (CD46,SLAM,NECTIN-4) after which the virus’ Fusion protein (F-Protien) allows the virus to fuse with the membrane and enter the cell. Since Measles is a single stranded RNA virus it is transcribed by RNA polymerase into a positive sense mRNA strand so it can be used to produce viral proteins. The virus can then reproduce and leave the cell to spread in the local tissues. Alveolar macrophages and dendritic cells take viruses from local tissue to local lymph nodes where they can enter the blood and spread to other organs.

Figure 1: General Structure of a virus

From first contact with the virus there is a 10-14 incubation period. This is followed by a Prodromal period for 3-4 days when Koplik spots and symptoms begin to appear- conjunctivitis (pink eye), cough and coryza (swelling in the mucous membrane) which precedes the Exanthem period of around 4 days in which a red blotchy maculopapular rash develops which progresses from the head to the extremities. Finally there is a 14 day recovery period in which the patient id afflicted with a persistent cough.Only during the Prodromal and Exanthem periods the patient is contagious, and once an individual has been infected by measles they are immune.

Figure 2: Koplik spots

Measles is diagnosed commonly using an enzyme-linked immunoassay testing for immunoglobulin M and G antibodies. An unvaccinated individual would mount an IgM response(1-2 months) then IgG response(longer term). If an individual has measles there will be a rise in the titre of either/both M and G antibodies. IgG and IgM tests are used to confirm the diagnosis. For an individual diagnosed with measles there is no antiviral drug to treat the ailment. Drugs to control symptoms and Vitamin A- to boost antibody response and reduce risk of complications- are given. As a disease that largely affects young children, complications can be severe including encephalitis, diarrhea and pneumonia. If contracted during pregnancy by the mother, it can result in spontaneous abortion, premature delivery or low birth weight.

Vaccinating against measles is important. A live attenuated virus, it is given twice to children at 12-15 months and 4-6 years old. Mothers pass measles antibodies to children through the placenta to their child and these antibodies last 9 moths which is why the vaccination is given at around 1 year of age. With a 95 % efficacy the MMR vaccination ( which offers protections against measles, mumps and rubella ) is one of the best in the market. For the vaccine to be effective, a large proportion of the population must be vaccinated to minimise the spread of the disease.

Despite evidence of the efficacy of the vaccination, since the publication of ‘Dr’ Andrew Wakefield’s paper in the Lancet suggesting the MMR vaccine predisposes a child to autism skeptisism around the vaccine has been growning leading increasing numbers of parents preventing their children to get vaccinated. Small sample size, the speculative nature of the conclusions, questionable funding for his research and ethically questionable practice were just some of the issues of a paper that should not have been published in the first place. Autism development and administration of the MMR vaccine both occur around the same time in childhood , a fact that was exploited by Wakefield to result in one of the most serious frauds of medical history. Parents across the world, shockingly, didn’t vaccinate their children against MMR leading to outbreaks in the UK in 2008-2009. Lack of trust in physicians and the availability of forums which breed fear about vaccinations on the internet factors that cause parents to refuse vaccinations for their children. A common statement in anti-vaccination circles is that the ‘parent knows best’. Whilst a patient’s autonomy should be respected, doctors must point out that the benefits outweigh the risks that vaccination poses (side effects are possible) -especially for the high efficacy MMR vaccination.

Figure 3: Cases of measles from 2010-present

Rhazes would be astonished to see the disease of his age, being almost wiped out across the world. The technology and science has arriver, however in countries with weak health care infrastructure the prevalence of measles is higher. What is missing abroad is the funding; it is rather counter intuitive that in developed countries like the UK individuals are refusing such an important and effective vaccine only to accept pseudoscience and doubt. Strengthening the doctor patient relationship and educating individuals are ways to combat this; what remains important in the pro and antivax debate is that patient autonomy is respected by their physician.

Bibliography

https://www.cdc.gov/vaccines/pubs/pinkbook/meas.html

https://www.nhs.uk/conditions/measles/

https://www.who.int/immunization/diseases/measles/en/

https://youtu.be/YBceTQ97FnM – Measles Pathology

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3136032/

https://norkinvirology.wordpress.com/2016/08/04/john-enders-the-father-of-modern-vaccines/

https://www.chop.edu/centers-programs/vaccine-education-center/vaccine-history/developments-by-year

https://www.who.int/news-room/fact-sheets/detail/measles

https://viralzone.expasy.org/556?outline=all_by_species

https://kidshealth.org/en/parents/test-immunoglobulins.html

https://youtu.be/lUWpWKVcmc4 – ELISA test

https://www.wsj.com/articles/measles-cases-top-last-years-total-11554152226

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