Assessment of the status of measles elimination from reported outbreaks: United States, 1997-1999.
The status of measles elimination is best summarized by evaluation of the effective reproduction number R; maintaining R<1 is necessary and sufficient to achieve elimination. Previously described methods for estimating R from the sizes and durations of chains of measles transmission and the proportion of cases imported were applied to the measles data reported for the United States in 1997-1999. These comprised 338 cases, forming 165 chains of transmission, of which 43 had >1 case. One hundred seven cases were classified as importations. All 3 methods suggested that R was in the range 0.6-0.7. Results were not sensitive to the minimum size and duration of outbreak considered (so long as single-case chains were excluded) or to exclusion of chains without a known imported source. These results demonstrate that susceptibility to measles was beneath the epidemic threshold and that endemic transmission was eliminated.
Gay
Nigel J
NJ
Health Protection Agency, Modelling and Economics Unit, Communicable Disease Surveillance Centre, London, UK. nigel.gay@hpa.org.uk.
De Serres
Gaston
G
Farrington
C Paddy
CP
Redd
Susan B
SB
Papania
Mark J
MJ
D018563:Disease Notification; D004196:Disease Outbreaks; D004198:Disease Susceptibility; D019353:Endemic Diseases; D006801:Humans; D008457:Measles / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control* / Q000635:transmission*; D008954:Models, Biological; D014195:Travel; D014481:United States