Zika virus, an infectious virus responsible for a global health emergency in 2016, could be just one mutation away from exploding into a new outbreak, according to new research in mice. The virus needs just a single change in its genetic code that would create a new variant and spread rapidly through the population, likely causing the devastating birth defects that affected so many infants in the previous outbreak.
Emerging viruses, particularly those that already pose a health risk to humans, are constantly monitored and experimented on to identify potential threats (and even treatments). Experts working with coronaviruses now propose theoretical changes to the virus genome that could alter its transmissibility, and other viruses like Zika are no different.
Zika virus is spread mainly by mosquitos and is relatively mild in symptoms. However, pregnant people infected with the virus transmit it to their unborn children, resulting in a condition called microcephaly that causes tiny heads and underdeveloped brains in the infant. A Zika epidemic that began in Brazil and affected the Americas between 2015 and 2016 caused over 3,500 cases of infant microcephaly, and the World Health Organization states it represents a “highly significant and long-term problem”.
Now, a new study published in the journal Cell Reports has identified a mutation in the possible evolution of Zika that could enable it to increase its transmissibility, even in countries that have an immunity to it from previous outbreaks. By using a mouse model and mosquitos to mimic the transfer of Zika between vector and human hosts, scientists discovered small genetic mutations that increased the infectious characteristics of the virus. Specifically, it created a variant that could evade immunity provided by past infection of dengue fever, a similar pathogen, suggesting the new mutation would enable Zika to re-emerge in countries previously affected.
"The Zika variant that we identified had evolved to the point where the cross-protective immunity afforded by prior dengue infection was no longer effective in mice,” said Professor Sujan Shresta, lead author of the paper, reports BBC News.
"Unfortunately for us, if this variant becomes prevalent, we may have the same issues in real life."
To be clear, this mutation has not been discovered in the wild yet and this paper acts as a warning for a possible future event, not an alert about an existing outbreak. The authors also state that this is simply a theoretical prediction that can pass between mice and non-human primate cells, and further investigation is needed to show it would present a danger to humans.
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