RIO DE JANEIRO, Nov. 28 (Xinhua) -- The number of Zika virus cases in Brazil fell 92.1 percent in 2017, but outbreaks remain possible as summer comes, the country's Health Ministry said Tuesday.
From January to November in 2017, 16,800 new cases of Zika virus infection were reported in Brazil, down from 214,100 cases in the same period of 2016, seeing a decrease of disease incidence from 103.9 cases to 8.2 cases for every 100,000 inhabitants.
In addition to Zika, the number of cases of dengue fever and chikungunya fever also fell respectively by 83.7 percent and 32.1 percent in Brazil this year. The three diseases are transmitted by the same bug, the Aedes aegypti mosquito, which is endemic to Brazil.
Despite the sharp fall in Zika cases, 357 towns in Brazil are still under outbreak risks as summer approaches, when Aedes aegypti mosquito reproduces faster.
Dengue fever can be lethal in its hemorrhagic form, and chikungunya can lead to chronic joint problems and other sequela. Zika is comparatively the mildest of the three diseases, yet it poses a significant danger to pregnant women.
When women are infected with Zika during gestation, their fetuses can develop malformations, mostly microcephaly. Two years ago when the disease was relatively new to Brazil, an outbreak of Zika led to a sharp increase in the number of microcephalic newborns.