Measles
Measles is the most contagious diseases among humans all over the world. Measles is caused by RNA virus known as Measles virus. All age group are susceptible for measles but low population immunity, high birth rates, high population density dwellers are more vulnerable especially younger age (Infant and pre-school children). It is a vaccine preventable disease.
Epidemiology:
Measles occurs as a seasonal disease in endemic areas, mostly occurs during dry season in tropical zones and in temperate zones it occurs during winter and early spring. Major epidemics occurred every 2-3 years earlier to measles vaccination in 1963 and it was estimated that more than 2 million deaths occurred globally each year. More than 95% of individuals of 15 years of age had been infected by measles virus.
Pathogenesis:
- Agent: Measles virus (Single stranded RNA virus)
- Host: Only Human
- Reservoir: No
- Route of transmission: Respiratory droplets
- Incubation period: 10-14 days but may ranging from 7-23 days
Clinical Presentations:
- Fever (39-40.5 degree C)
- Maculopapular rash
- Cough
- Conjunctivitis
- Coryza
- Malaise
Diagnosis:
- Diagnosis is mainly based on clinical sign presentations. There will be Koplik’s Spot (Bluish white spot on the oral mucosa opposite to 2nd Molar tooth) which is pathognomonic for measles.
- Confirmatory diagnosis is based on detection of anti measles virus IgM antibody by ELISA or the detection of measles virus RNA by RT-PCR (Reverse Transcriptase Polymerase Chain Reaction) from throat or nasopharyngeal fluid or urine.
Treatment:
There is no specific treatment for Measles, it is self limiting but some measures should be taken
- Patient isolation to prevent further spread which is most important
- Nutritional support to prevent malnutrition
- Vitamin A supplement (50000 IU for < 6 months of age, 100000 IU for 6-11 months of age, 200000 IU for ≥12 months of age)
- ORS (Oral Rehydration Salts) to prevent dehydration
- Antibiotics if secondary bacterial complications develop
Complication
- Pneumonia
- Diarrhoea
- Otitis Media
- Laryngo tracheal bronchitis
- Malnutrition
- Blindness
- Subacute Sclerosing Pan Encephalitis (SSPE)
Post exposure prophylaxis
- Measles vaccine may be administered within or after 72 hours of exposure if the susceptible is unimmunized or poorly immunized
- Human Immune globulin - may be given after measles virus exposure to the individuals with measles vaccine contraindicated, pregnant women and infants aging <6 months
Immunity
Immunity for measles may be developed either by natural exposure or by vaccination. After exposure to measles virus or vaccine cell-mediated immunity is must required to clear the virus once infection can occurred.
Long lasting, possibly lifelong, immunological memory following wild-type virus infection includes both continued production of measles virus-specific antibodies and the circulation of measles virus-specific CD4+ and CD8+ T lymphocytes. Although the levels of anti-measles-virus antibodies may diminish over time, the ability to rapidly increase secondary to humoral and cellular immune responses, ensures protection from infection. Infants can be protected temporarily by maternal anti-measles IgG antibsodies which cross the placenta to the fetus. Depending on the concentration of passively acquired maternal antibodies, infants are usually protected against measles for 6–9 months. However, infants whose mothers have vaccine-induced immunity receive less maternal antibody than infants whose mothers had had wild-type measles virus infection, resulting in a shorter duration of protection
Vaccine
Measles vaccine is live attenuated vaccine and was first licensed in 1963. Measles vaccine are available in combination as Measles-Rubella (MR), Mealses-Mumps-Rubella (MMR), Mealses-Mumps, Rubella-Varicella (MMRV).
Standard dose of Measles vaccine is 0.5 ml and usually administered subcutaneously. 2 doses are recommended for primary prevention and the dose schedule may vary from country perspective.
Measles Elimination
