Could a plant virus have found a way to infect humans?

It has always been assumed that plant viruses cannot infect animals, and vice versa, but plant viruses are known to be abundant in human faeces.

Now Didier Raoult at the University of the Mediterranean in Marseille, France, and his team think a pepper virus is making people sick, too.

They have found RNA from the pepper mild mottle virus in the faeces of 7 per cent of the 304 adults they tested. Those with the virus were more likely to report fever, abdominal pain and itching than those without it, his team found.


Not everyone is convinced, however. Because Raoult looked at many possible symptoms, he would be expected to find a few that randomly appear more common in virus-positive people, says Robert Garry, a virologist at Tulane University in New Orleans, Louisiana.

Moreover, in order to enter a cell and replicate, a virus must bind to a receptor on its surface, and a plant virus would be highly unlikely to recognise a receptor on a human cell, says Garry.

One possibility, Raoult says, is that the virus does not infect human cells directly. Instead, the naked viral RNA may alter the function of the cells through a mechanism similar to RNA interference, in which the presence of certain RNA sequences can turn genes on and off.

Raoult’s team is now working to gather more direct evidence that the virus does infect humans.

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0010041