Chapter 30 - Measles

Abstract

Measles is a highly contagious disease characterized by a prodromal illness of fever, cough, coryza, and conjunctivitis followed by the appearance of a generalized maculopapular rash. Measles virus is a nonsegmented, single-stranded, negative-sense RNA virus and a member of the Morbillivirus genus in the family of Paramyxoviridae. Although RNA viruses have high mutation rates, measles virus is an antigenically monotypic virus and the surface proteins responsible for inducing protective immunity have retained their antigenic structure. The public health significance is that measles vaccines developed decades ago from a single measles virus strain remain protective worldwide. Prior to the development and widespread use of measles vaccine, 30 million cases of measles were estimated to occur each year, resulting in more than 1 million deaths. Several live, attenuated measles vaccines are available, either as single-antigen vaccines or in combination with rubella and mumps vaccines (MR and MMR vaccines). Most of the currently used measles vaccines were derived from the Edmonston strain of measles virus that was isolated by Enders and Peebles in 1954. Measles vaccines are recommended for all susceptible children and adults for whom the vaccine is not contraindicated. Despite progress in reducing measles mortality, measles remains a major cause of vaccine-preventable death and an important cause of morbidity and mortality in children, particularly sub-Saharan Africa and in Asia. The ideal measles vaccine would be inexpensive, safe, heat-stable, immunogenic in neonates or very young infants, and administered as a single dose without needle or syringe. A number of vaccine candidates with some of these characteristics are undergoing preclinical studies, including DNA vaccines and various viral and bacterial vectored vaccines. The high infectivity of measles virus is a characteristic suitable to a biothreat agent. However, increasingly high levels of measles vaccination coverage throughout the world as part of accelerated measles control efforts would protect many from the deliberate use of measles virus as a biothreat agent. Genetic engineering of a measles virus strain that was not neutralized by antibodies induced by the current attenuated measles vaccines would likely have reduced infectivity, as suggested by the fact that wild-type measles viruses have not mutated to alter their neutralizing epitopes. Measles virus meets many of the biological criteria for disease eradication. Measles virus has no nonhuman reservoir, can be accurately diagnosed, and measles vaccination is a highly effective intervention. Where measles virus differs from smallpox and polio viruses is that it is more highly infectious, necessitating higher levels of population immunity to interrupt transmission. It remains unclear whether the threat from bioterrorism precludes stopping measles vaccination after eradication, but provision of a second opportunity for measles vaccination likely could be stopped following eradication.