Study suggests size of Zika epidemic may be underestimated

From Fundação de Amparo à Pesquisa do Estado de São Paulo:

A study supported by FAPESP and coordinated by researchers at the São José do Rio Preto Medical School (FAMERP) in São Paulo State, Brazil, suggests official statistics may underestimate the size of the epidemic caused by Zika virus. Some cases of Zika may be misreported as dengue, the authors also argue.

The team, led by Maurício Lacerda Nogueira, a member of the Zika Research Network (Rede Zika), performed molecular tests on blood samples from 800 people treated as suspected dengue patients at the emergency facility of Hospital de Base, São José do Rio Preto’s reference hospital, between January and August 2016.

The material was supplied by Hospital de Base, which is also FAMERP’s teaching hospital, and by the city’s health department.

The initial diagnosis, based on clinical symptoms and serological tests, was confirmed in only 400 samples. More than 100 of the cases analyzed were positive for Zika virus, and the virus that causes chikungunya fever was identified in one of the samples.

None of the three arboviruses transmitted by Aedes aegypti was found in the remaining samples (almost 300). The researchers suspect these patients probably had flu or some other viral disease. Their findings were published this month in the Journal of Clinical Virology.

“These results suggest the classic division usually made between symptoms – associating conjunctivitis with Zika and joint pain with chikungunya, for example – is only for classroom use. In practice, the symptoms can’t be separated like that,” Nogueira said. “It’s also practically impossible to distinguish between the three arboviruses with the serological tests currently used on a routine basis by laboratories and emergency services.”

Although new serological methods capable of distinguishing accurately between Zika and dengue antibodies have been developed, so far they are used only in academic research, he added.

The methodologies currently available …

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