SURVEILLANCE OF MEASLES IN ENGLAND AND WALES - IMPLICATIONS OF A NATIONAL SALIVA TESTING PROGRAM

The impact of a mass vaccination campaign against measles-rubella in E ngland and Wales was assessed using the results of a saliva test for m easles-specific IgM which was offered to all notified cases of measles . By means of clinical data supplied by the reporting doctors, we esti mated the sensitivity and specificity of various clinical case definit ions in predicting a confirmed case. A saliva sample was obtained with in the appropriate time period for 3442/7574 (45.4%) of notified cases ; the proportion confirmed by saliva testing was low and fell from 67/ 681 (9.8%) at the start of the campaign to 1/373 (0.3%) after 35 weeks . The specificity of all clinical case definitions was low, but was hi ghest at 41.1% (95% confidence interval, 39.2-43.0%) for the definitio n similar to that recommended in the USA. Extrapolating from cases obs erved during ongoing surveillance permits estimation of an annual noti fication rate for nonmeasles rash and fever illness. For countries wit h good measles control. a clinical case definition is too nonspecific for accurate surveillance. Laboratory confirmation of suspected measle s cases is required and saliva testing is an acceptable method. The co ntinued sensitivity of measles surveillance in England and Wales requi res that the incidence of notified rash and fever illness and the prop ortion of cases in which measles infection was excluded by laboratory testing be monitored.