A study conducted at the University of Helsinki in Finland has detected genetic material from the Zika virus in blood samples obtained from a pregnant woman weeks after the acute rash caused by the infection had passed. At this early stage of fetal development, severe brain abnormalities can be detected through neuroimaging, before the development of the intracranial calcifications and microcephaly previously associated with Zika virus infections, according to the researchers.
The study, published in the New England Journal of Medicine, is the first to report the isolation of infectious Zika virus from fetal tissue in cell culture. The tissue was obtained from a Finnish woman who was infected while visiting Central America during her 11th week of pregnancy. The researchers mapped the entire genome of the virus and discovered eight mutations, which distinguished the observed virus from Zika strains previously reported in Central America. “Some of these mutations may be associated with adaptations of the virus to the fetal brain,” said lead investigator Professor Olli Vapalahti.
The study results will help in the development of methods that can detect fetal damage associated with Zika virus infection during pregnancy, according to Vapalahti. “Our research also helps confirm the causal relation between the Zika virus and severe damage to the fetal central nervous system,” he said.
The Zika virus is a flavivirus spread by mosquitoes of the Aedes genus. It was discovered in Uganda in the 1940s in conjunction with surveillance for the yellow fever virus. Until the early 2000s, only sporadic reports of Zika virus infection were available. Since 2007, however, the virus has caused extensive epidemics in Pacific areas, and in 2015, it spread rapidly through South and Central America.
Zika virus infection causes an acute rash and fever, symptoms typical of other virus infections transmitted by mosquitoes, such as dengue and chikungunya. Even though these infections are typically mild, reports in late 2015 indicated that they could also affect the central nervous system, and that infection during pregnancy could be associated with microcephaly in newborns. For this reason, the World Health Organization declared a “public health emergency of international concern” in response to the Zika virus epidemic, as the agency had done during the Ebola virus and swine flu epidemics.
The recommended method for diagnosing Zika virus infection during the first week of illness includes detecting viral RNA and determining the presence of antibodies in blood samples. It is recommended that pregnant women undergo an ultrasound examination as well as a sampling of the amniotic fluid to determine the presence of Zika virus RNA.
Source: University of Helsinki; March 31, 2016.