Measles

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Causative Agents

 

Measles virus (MeV), member of Morbillivirus genus of Paramyxoviriade family, is a single-stranded, negative-sense RNA virus which causes fever, coughing, conjunctivitis, coryza as well as maculopapular rashes [1],[2]. Genome of the virus consists of 15.894 nucleotides, which can be categorized under 24 genotypes, depending on their variable 450 nucleotides [3]. Despite the variety of measles genotypes, there is only one dominant measles serotype [4]. There are two key envelope glycoproteins on the viral surface that are employed in the process of host cell-binding and invasion: Hemagglutinin (H) and Membrane Fusion Protein (F) [5].

 

Epidemiology

 

A recent study suggests that around 20 million people around the world are affected by MeV annually, of which are mainly located in the less developed areas of Asian and African countries [6], [7]. MeV is reported to cause the highest number of deaths among vaccine-preventable diseases [8]. Originally, lethality ratio is reported as low as 0.2% for those who are infected [9]; however, it may rise up to 10% due to malnutrition. Most of the lethal cases are less than five years old [7]. An estimated total of 158,000 of deaths, annually, were caused by measles globally [10].

 

Measles-caused complications are observed in a wide range from mild (diarrhea etc.) to more serious ones (pneumonia, bronchitis etc.) or even worse cases such as brain inflammation [11], [12]. Severity of the complications are strongly related to malnutrition, underlying immunodeficiency, pregnancy and vitamin A deficiency [13], [14].

 

Currently no specific treatment is addressed for measles as most of the infected cases will recover as the result of supportive treatments [11].

 

Modes of Transmission

 

MeV is localized in the nose and throat mucus of the infected people and transmitted mainly via person to person contact; therefore, it shows a high level of contagiousness with a rate of 90%. MeV from respiratory droplets of an infected individual can survive up to two hours in an airspace, which makes possible to get infected even if there is no actual person-to-person contact [15]. An infected person may start spreading the disease roughly from five days before and after the appearance of rash. The period of maximum contagiousness is thought to be during the late prodrome phase, when the patient is febrile and has respiratory symptoms [16], [17].

 

Measles is considered as a disease of humans as no other animal reservoir has been shown and not spread by any other animal species [7].

 

REFERENCES

1. Cohen BE et al, 2014, Viral causes of hearing loss: review for hearing health professionals, Trends in Hearing. 18: 2331216514541361

2. Atila TK et al, 2016, Towards Measles Elimination: Phylogenetic Analysis of Measles Viruses in Turkey (2012–2013) and Identification of Genotype D8, Journal of Medical Virology, DOI 10.1002/jmv.24548

3. Maurice D et al, 2013, Molecular characterization of measles viruses that circulated in Cameroon between 2010 and 2011, Virology Journal 201310:71.

4. Simpson RE, 1952, Infectiousness of communicable diseases in the household (measles, chickenpox, and mumps), Lancet,2(6734):549-54.,

5. Lu G et al, 2013, The receptors and entry of measles virus: a review. Sheng Wu Gong Cheng Xue Bao 29(1):1–9

6. Caserta MT, 2013, Measles, Merck Manual Professional. Merck Sharp & Dohme Corp.

7. Measles Fact Sheet No 286, WHO INT, November 2014, Retrieved 4 February 2015.

8. Kabra SK and Lodhra R, 2013, Antibiotics for preventing complications in children with measles, Cochrane Database of Systematic Reviews. 8: CD001477.

9. William A, 2011. Epidemiology and Prevention of Vaccine-Preventable Diseases (12 ed.). Public Health Foundation. pp. 301–323. ISBN 9780983263135.

10. Lozano R et al.,  2012, Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010, Lancet. 380 (9859): 2095–128. 

11. Gardiner WT, 2007, Otitis Media in Measles, The Journal of Laryngology & Otology. 39 (11): 614–617. 

12. Fisher DL, 2014, Measles-induced encephalitis, QJM. 108: 177–182.

13. Chen SSP, 2011, Measles (Report). Medscape.

14. National Institutes of Health Office of Dietary Supplements, 2013, Vitamin A, U.S. Department of Health & Human Services.

15. Bloch AB, 1985, Measles outbreak in a pediatric practice: airborne transmission in an office setting, Pediatrics. 1985;75(4):676