Possible new outbreak of Zika virus in Africa
Researchers warn of the possibility of a new outbreak of Zika virus, with a single mutation potentially sufficient to cause an explosive spread.
The disease caused a global medical emergency in 2016, as thousands of babies were born with brain damage after their mothers became infected during pregnancy.
US scientists say the world should be on the lookout for new mutations, and laboratory work, described in the journal Cell Reports, indicates that the virus can be easily transmitted, creating new variants.
Recent infection studies suggest that these variants may prove effective in transmitting the virus, even in countries that have built immunity to previous Zika virus outbreaks, says a team from the La Jolla Institute of Immunology.
Experts said the findings, while theoretical, were intriguing - and a reminder that viruses other than Covid could pose a threat.
About the Zika virus
Zika is spread by the bites of an infected Aedes aegypti mosquito, which is most active during the day. The insects are found throughout the Americas - with the exception of Canada and Chile, where it is too cold for them to survive - and across Asia.
While Zika is for most people a mild illness, and it doesn't have lasting effects, it can have serious consequences for babies in the womb.
If the mother becomes infected with the virus during pregnancy, it can harm the developing baby, causing microcephaly (an unusually small head) and brain tissue damage.
Although the virus is spread mostly by mosquitoes, it can also be transmitted through sexual contact.
Zika symptoms
Few people die from Zika and it is believed that only one in five infected people develop symptoms.
Symptoms can include fever, rash, and joint pain.
Since there is no cure, the only option is to reduce the risk of being bitten.
Scientists have begun work on a Zika vaccine to help protect a pregnant woman.
Mutations are possible
The researchers recreated what happens when Zika travels back and forth between mosquitoes and humans, using live cells and mice in their experiments.
When the Zika virus passed between the cells of mosquitoes and mice in the lab, small genetic changes occurred.
This meant that Zika was relatively easy to mutate in a way that would allow the virus to thrive and spread, even in animals that had some previous immunity to a similar mosquito-borne infection called dengue.
"The Zika variant we identified has evolved to the point where the protective immunity provided by previous dengue infection is no longer effective in mice," said lead researcher Professor Sujan Shrestha. "Unfortunately for us, if this alternative becomes mainstream, we may face the same problems in real life."
Professor Jonathan Ball, a virologist at the University of Nottingham, said: "We've heard a lot lately about the rapid development and emergence of coronavirus variants, but this is a timely reminder that morphology is a common feature shared by many viruses."
“This work shows how quickly a single letter change can arise in the genome sequence of a virus, and the stark effect it can have on the pathogenicity of the virus. But viruses that share these changes are not often seen in outbreaks, as the authors note. These intriguing ideas require further research."
Dr Claire Taylor, from the Society for Applied Microbiology, said: "Although these results have been seen in lab experiments and therefore have limitations, they do show the potential and remind us of the potential for worrisome variables to emerge during the normal Zika transmission cycle. Monitoring is important to follow viruses as they evolve." .
It may be possible to predict the variables that could cause major problems in the future and intervene early, she said.
Professor Paul Hunter, Professor of Medicine at the University of East Anglia, said previous Zika virus infection may still provide some protection against new variants - as seen with Covid.
