Scientists have warned that infection with the Zika Virus could have implications extending beyond unborn children; as new research shows the virus may have long-term implications for memory and learning in adults.

The Zika virus is mostly known for its disastrous consequences for unborn children, where the virus corrupts the growing brain tissue, leading to permanent brain damage. Although the virus can also infect adults as well, so far adults do not seem to suffer any damage to the brain as a result. However, due to the relatively recent emergence of the virus, it is difficult to know if the virus as any long-term consequences for adults. A team of scientists from the La Jolla Institute of Allergy and Immunology in California, USA have warned that the effects of the virus on adults may be harder to detect, and emerge more slowly.

Experiments performed on adult mice revealed that the virus is still capable of invading and surviving inside fully formed brains. Although unlike its manifestations in fetuses, where it attacks the whole brain, the attacks in adults are mostly focused on the memory and learning centers. The presence of the Zika virus in these two regions lead to brain cell death and reduced cell division, which would likely produce Alzheimer’s-like symptoms in adult humans. A member of the team, Professor Joseph Gleeson, from Rockefeller University, said:

‘‘It was very clear that the virus wasn’t affecting the whole brain evenly, like people are seeing in the fetus. In the adult, it’s only these two populations that are very specific to the stem cells that are affected by virus. These cells are special, and somehow very susceptible to the infection’’.

This discovery suggests that adults may still experience severe effects from Zika virus infection– it may be that their symptoms are subtler, and emerging over longer time periods, as compared to the virus’s rapid and dramatic effects on fetuses and infants.

As with all tests performed on animals, it is important to note that the behavior of the virus inside mice may not necessarily correlate to its behaviour in adult humans. It is unclear if the virus can damage adult humans in a similar way, or exactly how severe or permanent such damage would be. It is also quite likely that healthy adults would be able to mount a successful immune response to the virus, although adults with weakened immune systems may still be vulnerable.

Although the risks of the virus are still uncertain, Professor Gleeson has urged governments act cautiously: ‘‘the virus seems to be traveling quite a bit as people move around the world. Given this study, I think the public health enterprise should consider monitoring for Zika infections in all groups, not just pregnant women’’.

Further research is already underway to discover more about the effects of the Zika virus on adults.

– Greg Taylor, Correspondent (Science)

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