As of June 30 this year, there have been 1,674 confirmed cases of microcephaly linked to the Zika virus in five countries. Now, researchers who have created a new method for estimating who in the Americas is at risk of Zika virus infection say up to 1.65 million women of childbearing age in Central and South America could be infected by the end of the epidemic’s first wave.
The researchers - who come from the University of Southampton and the University of Oxford in the United Kingdom, as well as the University of Notre Dame in Indiana - published their findings in Nature Microbiology.
Zika virus is spread by the bite of an infected Aedes aegypti mosquito, which the US Centers for Disease Control and Prevention (CDC) describe as “aggressive daytime biters” that can also bite at night.
Because the virus has been associated with a range of fetal developmental conditions – including microcephaly - and there is no vaccine available, the epidemic poses major concerns, particularly for the nearly 15 million children born in the Americas each year.
Prof. Andrew Tatem, study author from the University of Southampton, notes that predicting how many childbearing women are at risk from Zika is very challenging, given that many cases do not show symptoms. An estimated 80% of Zika infections do not display signs of illness.
Currently in the US, Zika is not being spread by mosquitoes.
“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,” he adds.
The lack of symptoms, along with inconsistent case reporting, make case-based data unreliable, according to researchers, medicalnewstoday.com reported.
The team designed an improved method for estimating the risk that Zika presents, by taking into account ecological theories such as herd immunity and basic reproduction number, which is the estimated number of new people that one infected person can infect.
They examined the impact of the virus at local levels, at a scale of 5 sq km, and also considered disease patterns shown in similar epidemics - such as those seen with dengue and chikungunya viruses.
Additionally, researchers factored in how the virus is transmitted, climate conditions, and virus incubation periods.
By using existing data on population, fertility, pregnancies, births, and socioeconomic conditions, researchers were able to model the potential scale of the spread of Zika.
Researchers also found that over 90 million infections could result from the initial spread of Zika in Latin America and the Caribbean and that Brazil is expected to have the largest total number of infections, by more than threefold, given its size and conditions for transmission.
