Up to 1.65 million Zika infections predicted in next 2-3 years, in worst-case-scenario

Liz Meszaros, MDLinx | July 27, 2016

In Central and South America, predictions are that up to 1.65 million women of childbearing age may be infected by the Zika virus within the next 2 to 3 years of the epidemic, according to model-based projections conducted by researchers from the WorldPop Project and Flowminder Foundation, University of Southampton; the University of Notre Dame, Notre Dame, IN; and the University of Oxford, Oxford, United Kingdom.

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Zika virus projections

Zika virus projections

Map showing the projected number of Zika infections in childbearing women. Photo: University of Southampton.

In Latin America and the Caribbean, they predicted over 90 million infections, with Brazil thought to bring the largest total, by over 3-fold, because of its size and suitable environment for transmission.

Yet even after making their predictions, which are published July 25, 2016, in the journal Nature Microbiology, these researchers stressed that these numbers are representative of a worst-case scenario. Also important is that no data from the current epidemic were used. For their modeling, researchers relied instead on data and disease patterns shown in similar dengue virus—which is very similar to Zika—and chikungunya epidemics from the past, and other factors, such as mode of transmission, climate, and incubation time.

They combined this with existing data for the region on population, fertility, pregnancies, births, and socioeconomic conditions, and came up with this model of the possible scale of the spread of the Zika virus, with estimates reflective of thousands of cumulative localized projections of infections per every 5-x-5-kilometer grid cell across Central and South America.

“It is difficult to accurately predict how many child-bearing women may be at risk from Zika because a large proportion of cases show no symptoms. This largely invalidates methods based on case data and presents a formidable challenge for scientists trying to understand the likely impact of the disease on populations,” said lead author Andrea Tatem, BSc, professor of geography and environment, at the University of Southampton, and director of the WorldPop and Vector-borne Disease Airline Importation Risk research projects, and co-director of the Flowminder Foundation.

“These projections are an important early contribution to global efforts to understand the scale of the Zika epidemic, and provide information about its possible magnitude to help allow for better planning for surveillance and outbreak response, both internationally and locally,” Tatem concluded.

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