As of 21 November, 739 cases of microcephaly, a condition associated with underdeveloped brains, were being investigated in nine northeastern states, according to the World Health Organization.
Last week, Brazil’s health ministry confirmed the link between the virus and the microcephaly cases. It is calling for a national effort to contain the mosquito, Aedes aegypti, that spreads Zika, as well as dengue fever and chikungunya.
The state of Pernambuco has been particularly badly affected, the Pan American Health Organization said, with 140 babies born with microcephaly this year, compared with ten cases in 2014.
“It was already known that the virus affects the nervous system, but until now we didn’t know it could cause foetal malformations.”
Rivaldo Venâncio da Cunha, Oswaldo Cruz Foundation
Although Zika virus disease can cause rashes and fever, in three-quarters of cases, an infected person has no symptoms. The disease reached Brazil last year in the wake of increased travel into the country during the 2014 Football World Cup. A first large-scale outbreak was reported in Bahia state in April.
“It was already known that the virus affects the nervous system, but until now we didn’t know it could cause foetal malformations,” says Rivaldo Venâncio da Cunha, an infectious diseases researcher at the Oswaldo Cruz Foundation in Brazil. “We found the virus in the amniotic liquid of two women pregnant with microcephalic babies, which is a strong indication that the virus can cause problems if a woman is infected in the first trimester of the pregnancy.”
The risks of brain damage are corroborated by health authorities in French Polynesia, which last week reported an unusual rise of central nervous system malformations in babies — which coincided with zika outbreaks in the nation in 2014 and 2015. The Zika virus remained limited to Africa and Asia until 2007, when there was an outbreak on the Pacific island of Yap, followed by the ongoing outbreak in French Polynesia.
Microcephaly happens when the brain fails to develop fully in the womb, usually causing severe disabilities. As well as resulting from infection, the condition can also be caused by alcohol and drug abuse, and genetic abnormalities.
“The Brazilian outbreak is the first epidemic of Zika that affected a very large population, making rare events, like microcephalic babies, common enough to be noticed,” says Venâncio.
According to the European Centre for Disease Prevention and Control, the growing prevalence of Zika virus in Brazil should have implications for prenatal care. A spokesman said local health professionals should be asked to be aware of the possible association between Zika virus infection and microcephaly.
“There is neither a vaccine for preventative or curative medication against Zika virus infection at this point,” the spokesman said.
Ann Powers, the head of arboviral diseases at the Centers for Disease Control and Prevention in the United States, told SciDev.Net that any country home to mosquitoes that carry vector-borne diseases is at risk from zika. "Zika virus is certainly moving rapidly in many parts of the world and, because there have been few historical outbreaks documented, we are learning more about the virus each time new cases arise,” she said.