The primary mosquito that spreads Zika virus -- aedes aegypti -- might also simultaneously transmit chikungunya and dengue viruses with a single bite, says a study that sheds new light on co-infection.

"A mosquito, in theory, could give you multiple viruses at once," said Claudia Ruckert, post-doctoral researcher at Colorado State University in the US. In the study, published in the journal Nature Communications, the team infected mosquitoes in the lab with multiple kinds of viruses to learn more about the transmission of more than one infection from a single mosquito bite. The results showed that mosquitoes in the lab can transmit all three viruses simultaneously, although this is likely to be extremely rare in nature."Dual infections in humans, however, are fairly common, or more common than we would have thought," Ruckert added.

Further, all the three viruses were found to replicate in a really small area in the mosquito's body.One virus proved to be dominant and outcompeted the others in the midgut of the mosquito where the infections establish and replicate before being transmitted to humans."When these mosquitoes get infected with two or three different viruses, there's almost no effect that the viruses have on each other in the same mosquito," Ruckert said. 

However, there's no reason to believe that these co-infections are more severe than being infected with one virus at a time."There's no strong evidence that co-infection of humans results in infections that are clinically more severe," Ruckert said.On the other hand, "there might be some indications, but it is still fairly unknown what the effect is from co-infection," she stated.In addition, it is also likely that co-infections in humans are significantly under-diagnosed, the researchers noted.