Measles virus, a paramyxovirus is one of the main causes of death in children in developing countries and responsible for some deaths in industrialized nations. Infection resorts to immunosuppression, making the host more susceptible to secondary infections with a range of viral and bacterial pathogens and causing most measles associated (Carter et al, 2007). Measles is an acute highly viral infectious disease. Before vaccines, infection was nearly universal during childhood. It has no known animal reservoir and no asymptomatic carrier state has been recorded (Roy P et al, 2015). Measles is still a common and fatal disease especially in developing countries. It is primarily transmitted through large respiratory droplets. It is highly infectious, with greater than 90% secondary attack rates among susceptible persons (CDC, 2015). It infects nearly 30 million children per year worldwide. Complications related to pneumonia, diarrhea and malnutrition usually cause death (Orenstein et al, 2004). WHO estimates that of the approximately two- thirds of the global burden of death due to measles, almost 1,36,000 (range: 98,000 to 1,80,000) occurred in the South East Asian Region in 2007, with most of in India. India had 47% of estimated global measles mortality in 2010 (Simon et al, 2012).
Infection is very contagious and usually through aerosol route. Initially, the Virus replicates in the respiratory tract, then spreads to lymphoid tissues. Viremia and spread to a variety of epithelial sites follows. About 1-2 weeks after infection disease symptoms develop.
Diagnosis includes: 1) clinical picture (history of exposure and upper respiratory tract symptoms, Koplik's spots and rash); 2) confirmatory tests. Disease is confirmed with RT-PCR serodiagnosis, isolation. Serology diagnosis by IgG is simpler than isolation but two samples are needed (one 10-21 days post rash) so it takes longer. An IgM test is now available.
Almost all individuals infected are symptomatic. Only one serotype exists. A single natural infection gives life-long protection. Inhalation is the main route of infection. It is highly contagious – the maximum period of contagiousness is 2-3 days before the onset of rash (Hunt M, 2009).
Problems associated with measles infection
A high fever is usually the first sign of infection with measles, which begins after incubation period which is about 10 to 12 days after exposure to the virus, and lasts for about 4 to 7 days. A runny nose with cough, conjunctivitis, and koplik can develop in the initial stage. After several days, a rash apears, often on the face and upper neck, averagely, the rash occurs 14 days after infection (in a range of 7 to 18 days). Over about 3 days, the rash spreads, it eventually gets to the hands and feet. It lasts for 5 to 6 days, and then fades (Roy P et al, 2015).
Most measles-related deaths are as a resort of associated complications. Complications are more common in children under the age of 5, or adults over the age of 20. The severe complications are blindness, severe diarrhea and resulting dehydration, ear infections, and severe respiratory infections such as pneumonia. Measles could be severe among poorly nourished young children, especially those with insufficient vitamin A, or the immune-compromised (WHO measles factsheet, 2015).
In a very small proportion, the virus establishes in the brain and, after a long period of incubation, causes a degenerative pattern of changes in brain function, this includes loss of higher brain activity, death is inevitable. Two related but different diseases result from neural infection, Measles Inclusion Body Encephalitis (MIBE) and Sub-acute Sclerosing Pan Encephalitis (SSPE).
MIBE occurs in approximately 1 in 2000 cases of infection, a chronic progressive encephalitis which occurs in young adults and children and is associated with a persistent measles virus infection. MIBE can be fatal with the survival time after diagnosis being an average of 3 years. It is usually a seen in immunocompromised patients and is associated with early primary infection usually before two years of age.
SSPE a slowly progressive neurological degenerative disease, occurs in approximately 1 in 100,000 cases. It is associated with a long term persistent measles virus infection that leads to death many years after the first infection (Dimmock et al, 2015).
Available control measures
A live attenuated virus vaccine (grown in chicken embryo fibroblast culture) is currently recommended to be given to children at twelve to fifteen months, Younger children do not show a strong immune response to the vaccine. A Second dose is given at about four to six years of age. Thus, reducing the number of persons who are susceptible due to failure of primary vaccine. Vaccination gives long term immunity and the vaccinee does not spread the virus. Immune serum globulin can be used for at risk patients (less than 1 year old, or with impaired cellular immunity) during an outbreak (Hunt M, 2009). Measles virus has not changed over its known history of about fifty years, the same level of protection is still reached by the original vaccines. The polio and measles viruses are stable when compared with HIV-1 and the influenza virus (Dimmock et al, 2007). Although the vaccine can cause fatal giant cell pneumonia in those with severely compromised cell-mediated immunity (Hunt M., 2009).
Challenges faced with global ambition of completely eliminating measles
The feasibility of measles eradication has been proven by the Region of the Americas, where elimination of measles and interruption of transmission has been achieved and sustained since 2002 (WHO Global Eradication of Measles, 2015). Despite the success in global measles control, the progress in reduction of the numbers of measles cases and deaths became stagnant between 2008 and 2010. This is was mostly due to prolonged measles outbreaks in Africa and Europe and the high burden of the disease in India. The number of measles cases in western European countries, rose from 7,499 in 2009 to over 30,000 in 2010 and 2011, this contributed to an increase the number of reported cases globally. During the same period, twenty-eight countries in sub-Saharan Africa were affected in a widespread resurgence (CDC, Eliminating measles, Rubella and CRS worldwide, 2015).
The eradication of measles is faced with so many challenges, some of the key challenges include:
- Maternal antibody fast rate of waning. A large number of children are left unprotected before the first dose because of the fast rate of waning of these maternal antibodies (Adu, 2008).
- Injectable nature of vaccine. There are problems with vaccine administration. Unlike the polio vaccine, the measles vaccine is administered with the injection, so it is not easy to administer. A large number of workforce are to be trained for vaccine administration. A very good solution to this problem would be the may be use of aerosol technique which, this can also be used by field workers. The acceptability of the vaccine may be improved through this method, since it would not require the use of injections (Roy P et al, 2015).
- Adverse reaction and reversion to virulent strain. The chances of adverse reactions to the live vaccine need to be addressed. Maintaining proper cold chain during storage and transportation of vaccine should also be considered (Roy P et al, 2015).
- Other competing priorities. The availability of qualified staff and funds are affected by competition from other health programs.There are competing priorities like streamlining of newer vaccines, polio eradication and other health initiatives (Roy P et al, 2015).
- Population displacement and migration. Population displacement and migration are challenges a measles eradication initiative would also face. Presently, there are large displaced populations in urban areas. Current eradication programs may face greater challenges than earlier programs as a result of exponential increase in trans- migration (United Nations Population Fund, 2015).
- Political instability. In several countries particularly Somalia and Afganistan, Sierra Leone, part of Parkistan, Congo, Sudan, Ethiopa and Liberia political instability and armed conflicts cause vaccination to be logistically unpredictable and difficult. In addition, Nigerian internal politics in the boycott of the 2003 immunization, were ramifications from the arena of international politics (Okonko et al, 2009).
- Terrorism and War. The main measles- endemic countries are at war, and the world spends more on arms than ever before. Both real and perceived terrorism, makes the situation more complex. As a resort, reaching high rates of vaccination coverage in areas affected by conflict will be very dangerous and difficult (Roy P et al, 2015).
- Low vaccination rates and surveillance. It is essential to maintain excellent vaccination coverage with high quality surveillance. Overcoming this, will be critical in dealing with importations of measles virus, so long as the measles virus is still endemic in other parts of the world (Andrus, 2011).
- Poor maintenance of high population immunity. Maintaining a high population immunity with excellent coverage and laboratory networking that is efficient for high- quality surveillance would deal with the problem of the importation of measles virus into countries where it has been eliminated (Ministry of Health and Family Welfare, 2004).
- The changing epidemiology of measles. The increased transmission of measles among adolescents and adults as a result of the changing epidemiology of measles should also be considered (Roy P et al, 2015).
To eradicate measles, research has shown the need to have homogeneous population immunity of ≥93% (WHO Global Immunization Vision and Strategy, 2005). Elimination of measles requires immunization coverage of at least 96% of children aged less than one year and also the prevention of accumulation in the immunity gap (Roy P et al, 2015). Three criteria are biologically important for the feasibility of the eradication of a disease, measles meets all: 1) humans are the only reservoir; 2) existence of accurate diagnostic tests; 3) an practical and effective intervention is available at an affordable cost. It can be concluded, that measles eradication is a very challenging but feasible target. Exponential increase in commitment and resources is an essential requirements, if the measles eradication initiative should be pursued. To achieve measles eradication, all the regions and countries of the world will have to work together.