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Zika epidemic may have peaked in Latin America, model suggests
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A model of virus transmission suggests the Zika epidemic in Latin America may have already reached its peak.
Neil M. Ferguson, PhD, professor of mathematical biology and head of the department at Imperial College London School of Public Health, and colleagues used the transmission model to predict the virus’ duration, specifically in Central and South America. The model combines factors that may determine the scale and spread of an emerging infection in naive populations. According to the researchers, three key factors include: transmissibility of infection, the generation time — or the time between sequential rounds of infection — and large-scale connectivity of human population, which is currently affected by vast human mobility.
Zika epidemic expected to end in 3 years
Based on the three key factors and the time between infection cycles, Ferguson and colleagues estimate that the current Latin American Zika epidemic will be over in 3 years, with “seasonal oscillations” in the incidence of disease driven by variation in mosquito populations and transmissibility. They predict that herd immunity will delay the next Zika outbreak for more than a decade.
“Modeling gives insight into how the age distribution of infection will evolve over time — of particular relevance given the risk of congenital Zika syndrome and microcephaly,” the researchers wrote in Science. “During the initial epidemic, we would expect all ages to be equally affected unless exposure and/or susceptibility vary substantially with age.”
According to the researchers, the mean age of those who become infected in future epidemics would decrease due to immunity acquired by older people with prior exposure to the virus.
“However, our analysis suggests that this effect is unlikely to be sufficient to prevent ongoing and substantial risk to pregnant women in future epidemics,” they wrote.
Ferguson and colleagues noted that advising against pregnancy to avoid adverse birth outcomes associated with Zika virus infection may not be feasible in the long-term, and traditional insecticide-based vector control in the past has been insufficient to stop dengue outbreaks and may actually interfere with herd immunity. The researchers recommended detailed local monitoring of the current Zika epidemic so that local advisories and delays in pregnancy are more feasible and appropriate.
“Long-term cohort studies can provide longitudinal data on individual variation in exposure and clinical and immunological outcomes,” they wrote. “Our analysis suggests that there is limited time to initiate such studies in the current epidemic before incidence may be insufficient to measure impacts.”
What is currently known about Zika
In a separate report that was also published in Science, Justin Lessler, PhD, associate professor in the department of epidemiology at Johns Hopkins Bloomberg School of Public Health, and colleagues summarized current research on Zika virus.
Increased evidence suggests Zika may be responsible for other fetal complications in addition to microcephaly, such as intracranial calcifications, ventriculomegaly, ocular impairment, brainstem hypoplasia, intrauterine growth restriction and fetal demise, according to Lessler and colleagues.
Human and mosquito genetics may play a role in how quickly the virus spreads and fluctuates, they said, and a Zika vaccine may be the best way to protect at-risk populations in preparation for future outbreaks instead of waiting for the virus to simply dissipate.
“New threats from infectious diseases may emerge from unexpected places, and we need strategies in place we can roll out to rapidly gain an understanding of the transmission, pathogenesis and control of previously little known pathogens to protect global public health,” Lessler and colleagues wrote. – by Kate Sherrer
Disclosure: Infectious Disease News was unable to confirm relevant financial disclosures at the time of publication.
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