The Ministry of Health (MOH) describes the Zika virus infection as generally a mild and self-limiting illness, but that rare, serious neurological complications have been reported. MOH’s advisory is especially focused on pregnant women and cautions that Zika virus infection can cause microcephaly in the unborn foetus of pregnant women.

A new study in mice however, indicates that Zika could also affect parts of the adult brain and “wreak havoc” on the brains of adults and cause major, lasting damage. The study published in Cell Stem Cell by US researchers found that the virus targets stem cells in parts of a fully grown mouse brain responsible for learning and memory and stops them proliferating.

Joseph Gleeson, a neurologist at Rockefeller University in New York and an author of the paper said: “Based on our findings, getting infected with Zika as an adult may not be as innocuous as people think.”

Professor Sujan Shresta, another member of the team from the La Jolla Institute of Allergy and Immunology in California, USA, said: “Zika can clearly enter the brain of adults and can wreak havoc. But it’s a complex disease – it’s catastrophic for early brain development, yet the majority of adults who are infected with Zika rarely show detectable symptoms. Its effect on the adult brain may be more subtle, and now we know what to look for.”

If Zika targets newborn brain cells, adults may be at risk, too, reasoned Professor Gleeson. “In more subtle cases, the virus could theoretically impact long-term memory or risk of depression, but tools do not exist to test the long-term effects of Zika on adult stem cell populations,” he said.

“Given this study, I think the public health enterprise should consider monitoring for Zika infections in all groups, not just pregnant women.” he added.

The scientists are still unsure about the extent of which their study in mice would apply to humans, or how permanent any damage sustained as a result of the virus might be. But they say that further work must be done to find out if Zika could cause long term Alzheimer-like mental impairment in adults.