Sarah F Ackley1,2, Jill K Hacker3, Wayne T A Enanoria2, Lee Worden1, Seth Blumberg1,4, Travis C Porco1,2,5, Jennifer Zipprich3. 1. Francis I. Proctor Foundation, University of California, San Francisco. 2. Department of Epidemiology and Biostatistics, University of California, San Francisco. 3. California Department of Public Health, Richmond. 4. St Mary's Medical Center, University of California, San Francisco. 5. Department of Ophthalmology, University of California, San Francisco.
Abstract
Background: Substantial heterogeneity in measles outbreak sizes may be due to genotype-specific transmissibility. Using a branching process analysis, we characterize differences in measles transmission by estimating the association between genotype and the reproduction number R among postelimination California measles cases during 2000-2015 (400 cases, 165 outbreaks). Methods: Assuming a negative binomial secondary case distribution, we fit a branching process model to the distribution of outbreak sizes using maximum likelihood and estimated the reproduction number R for a multigenotype model. Results: Genotype B3 is found to be significantly more transmissible than other genotypes (P = .01) with an R of 0.64 (95% confidence interval [CI], .48-.71), while the R for all other genotypes combined is 0.43 (95% CI, .28-.54). This result is robust to excluding the 2014-2015 outbreak linked to Disneyland theme parks (referred to as "outbreak A" for conciseness and clarity) (P = .04) and modeling genotype as a random effect (P = .004 including outbreak A and P = .02 excluding outbreak A). This result was not accounted for by season of introduction, age of index case, or vaccination of the index case. The R for outbreaks with a school-aged index case is 0.69 (95% CI, .52-.78), while the R for outbreaks with a non-school-aged index case is 0.28 (95% CI, .19-.35), but this cannot account for differences between genotypes. Conclusions: Variability in measles transmissibility may have important implications for measles control; the vaccination threshold required for elimination may not be the same for all genotypes or age groups.
Background: Substantial heterogeneity in measles outbreak sizes may be due to genotype-specific transmissibility. Using a branching process analysis, we characterize differences in measles transmission by estimating the association between genotype and the reproduction number R among postelimination California measles cases during 2000-2015 (400 cases, 165 outbreaks). Methods: Assuming a negative binomial secondary case distribution, we fit a branching process model to the distribution of outbreak sizes using maximum likelihood and estimated the reproduction number R for a multigenotype model. Results: Genotype B3 is found to be significantly more transmissible than other genotypes (P = .01) with an R of 0.64 (95% confidence interval [CI], .48-.71), while the R for all other genotypes combined is 0.43 (95% CI, .28-.54). This result is robust to excluding the 2014-2015 outbreak linked to Disneyland theme parks (referred to as "outbreak A" for conciseness and clarity) (P = .04) and modeling genotype as a random effect (P = .004 including outbreak A and P = .02 excluding outbreak A). This result was not accounted for by season of introduction, age of index case, or vaccination of the index case. The R for outbreaks with a school-aged index case is 0.69 (95% CI, .52-.78), while the R for outbreaks with a non-school-aged index case is 0.28 (95% CI, .19-.35), but this cannot account for differences between genotypes. Conclusions: Variability in measles transmissibility may have important implications for measles control; the vaccination threshold required for elimination may not be the same for all genotypes or age groups.
Authors: Seth Blumberg; Lee Worden; Wayne Enanoria; Sarah Ackley; Michael Deiner; Fengchen Liu; Daozhou Gao; Thomas Lietman; Travis Porco Journal: PLoS Curr Date: 2015-05-07
Authors: H Sittana El Mubarak; Selma Yüksel; Geert van Amerongen; Paul G H Mulder; Maowia M Mukhtar; Albert D M E Osterhaus; Rik L de Swart Journal: J Gen Virol Date: 2007-07 Impact factor: 3.891
Authors: Nicklas Sundell; Leif Dotevall; Martina Sansone; Maria Andersson; Magnus Lindh; Thomas Wahlberg; Tobias Tyrberg; Johan Westin; Jan-Åke Liljeqvist; Tomas Bergström; Marie Studahl; Lars-Magnus Andersson Journal: Euro Surveill Date: 2019-04
Authors: Lee Worden; Sarah F Ackley; Jennifer Zipprich; Kathleen Harriman; Wayne T A Enanoria; Rae Wannier; Travis C Porco Journal: Epidemics Date: 2019-11-10 Impact factor: 4.396