Key Points at a Glance
- The bites that mosquitoes leave on our skin usually itch uncomfortably for a few days, but they aren't dangerous.
- Until now, native mosquito species have rarely been suspected of transmitting diseases.
- But that has changed, even though the symptoms have generally been tolerable so far.
- The situation is different when it comes to exotic mosquitoes that have made their way to Europe and Switzerland.
Sometimes, we realize our blood has been drawn very soon after a mosquito bite. Intense itching sets in quickly, and it’s not uncommon for relatively large welts to appear on the skin—welts that can also become quite hot and may not subside for several days. Yet a mosquito bite is usually harmless. However, it doesn’t always stop at itching and swelling—mosquito species introduced from Asia, in particular, sometimes transmit dangerous pathogens.
West Nile virus: the mosquito isn't necessarily the problem
The West Nile virus has only been identified in Europe in the past few years. This potentially deadly virus causes a flu-like illness that usually begins abruptly and is accompanied by fever; the incubation period after a mosquito bite is about two to 14 days. In severe cases, the virus can also lead to meningitis. Fortunately, almost all cases observed to date have been mild and harmless.
In fact, the imported mosquitoes wouldn’t be the problem at all if it weren’t for migratory birds. According to experts, it is the birds that carry pathogens such as the West Nile virus. The exotic insects merely act as vectors—first they bite the birds, then humans or horses, thereby ensuring that the viruses find new hosts. Climate change is causing an unfortunate side effect: because it’s getting warmer and warmer in our latitudes, pathogens like the West Nile virus are multiplying more quickly in mosquitoes. We’re not quite there yet, but it could come to that.
What diseases do mosquitoes transmit?
So it’s important to know: The West Nile virus is most likely introduced by migratory birds—but it is transmitted by all kinds of mosquitoes, including our native species. However, other viruses have also been detected in these mosquitoes, such as the Batai virus, the Sindbis virus, and the Usutu virus, which is related to the West Nile virus.
At the same time, invasive mosquito species have become established in our region, such as the Asian bush mosquito, the Asian tiger mosquito, and the Korean bush mosquito. They are also carriers of these and other viruses, which generally cause mild infections with fever and cold-like symptoms, as well as headaches in most cases. More dangerous are Zika and dengue fever, which are also transmitted to humans by these mosquitoes. However, there is no reason to panic: fortunately, the Swiss climate prevents the transmission of these viruses in many cantons and regions.
The risk is already higher in warm regions
However, this does not apply to warmer regions. In warm parts of Germany, as well as in Ticino, the tiger mosquito and the bush mosquito are already established and are considered impossible to eradicate. And in these warm areas, disease transmission is more likely because the higher temperatures cause the mosquitoes to carry more pathogens.
But even if the worst-case scenario doesn’t materialize and no viruses are transmitted, you still wouldn’t want to be bitten by these introduced mosquito species: Their bites are more painful than those of our native species and usually result in larger marks on the skin. Allergic reactions are also more common when bitten by invasive mosquito species.
