Is the Zika virus spread by house flies?
The simple answer to this question is: no, the Zika virus is not spread by houseflies. To the best of our knowledge, it is spread by mosquitoes. Usually, these mosquitoes are of the genus Aedes.
The more interesting question is:
When we think about organisms spreading diseases, there is a particular term that we use – vectors. So what we know is that Aedes mosquitoes are vectors for the Zika virus. So our question above can be reframed as: can houseflies act as a vector for the Zika virus?
To answer that question, we need to understand that vectors do three things:
(1) they acquire the pathogenic microbes,
(2) they maintain these microbes (in other words, they allow them to survive or multiply), and
(3) they transmit the microbes.
The female Aedes mosquito feeds on human blood. During this process, it can acquire the virus from the blood of an infected human being. The virus then replicates in the mosquito’s gut, and then in its salivary glands. This takes about 5-10 days. After this, if the mosquito bites another human, then the virus can transmit to that human from the salivary glands of the mosquito.
So, the question now is:
Answer: Probably not, because in order to acquire and transmit the virus, the fly would need to feed on human beings. Since we know that houseflies do not feed on humans, we can safely conclude that they cannot acquire and transmit the virus.
Note that flies can and do act as vectors for other disease-causing pathogens, like the Salmonella bacteria (which can cause typhoid and salmonellosis in humans), Vibrio cholerae bacteria (which can cause cholera), Mycobacterium tuberculosis (which can cause TB), and Bacillus anthracis (causes anthrax). Houseflies can carry these organisms on their hair, mouthparts, vomit, and faeces. These are mechanically transmitted to food, contaminating it with the pathogens. Thus flies can act as vectors, but not for the Zika virus, which seems to be transmitted through body fluids like blood.
Finally, an interesting bit of trivia – mosquitoes are also a type of fly! In fact, the word mosquito is a combination of the Spanish words mosca (fly) and -ito (a suffix indicating small). So a mosquito is literally a “little fly”!
If mosquitoes are also a type of fly, one question is – how many different kinds of flies are there? As it turns out, there are thousands of species of flies alone! Click on any of the following links to learn more about flies: