Mosquitoes Chasing and Biting: A Hidden Danger Signal

In the vast crowd, why do mosquitoes “bite” you? It turns out that unique body odor may be the reason why you continue to be attractive to mosquitoes.

‍On June 30, a new study published in the journal “Cell” by Professor Cheng Gong’s team from Tsinghua University verifies the above point of view. People or animals infected with dengue virus are more favored by mosquitoes. On this basis, the team also proposed a strategy that promises to prevent outbreaks of mosquito-borne diseases…

The threat of infectious diseases is huge

As soon as summer arrives, mosquitoes will follow.

This annoying creature not only brings endless noise and itching to humans, but also spreads a large number of mosquito-borne viruses, causing widespread infectious diseases (including malaria, yellow fever, dengue fever, etc.). Worldwide, nearly one million people die from it every year.

Dengue virus and Zika virus are both common mosquito-borne viruses.

Dengue fever caused by the former is one of the most widespread viral infectious diseases in the world. It is mainly carried by the Aedes mosquito and spreads in tropical (and occasionally subtropical) regions, causing rashes, fever and pain in mild cases, bleeding and even death in severe cases. According to the National Institutes of Health (NIH), more than 50 million cases of dengue fever occur around the world each year, killing about 20,000 people, mostly children.

The latter, which host another mosquito of the same genus, are relatively less likely to cause serious disease in adult populations. However, it is inextricably linked to severe birth defects in newborns. A recent Zika outbreak in South America has caused thousands of infected pregnant women to give birth to microcephaly babies.

For a long time, mankind has made unremitting efforts to prevent mosquito-borne diseases. However, due to the special infection mechanism of the virus, the relevant vaccine has not yet come out.

It is for this reason that clarifying the mechanism of the rapid spread of mosquito-borne viruses and taking effective blocking measures has become the top priority.

Locate infected people by smell

The continuation of the virus relies on the continuous two-way transmission between humans and mosquitoes. In other words, if mosquitoes always choose to “take blood” from uninfected people to eat, the virus will have a hard time surviving.

Mosquito-borne virus transmission cycle.

The research team speculates that the reason why mosquito-borne viruses spread quickly and are difficult to eradicate is most likely because mosquitoes have a way to accurately locate infected people in the vast crowd. They then compared dengue-infected mice with healthy mice and found that mosquitoes did prefer to infect mice.

But why? After digging deeper, the team focused on a volatile molecule called acetophenone.

It turned out that whether mice or humans, after being infected with dengue virus, the content of acetophenone molecules in their odors increased significantly. This molecule can activate the mosquito’s olfactory nervous system, allowing the mosquito to “hear the news” and lock on to the target and run immediately. After applying different concentrations of acetophenone to human arms, the researchers also determined that the higher the concentration of acetophenone, the more attractive the arm was to mosquitoes.

This shows that changing the odor of the host is a necessary means for mosquito-borne viruses to improve their own transmissibility.

New Ideas for Prevention and Control of Mosquito-borne Infectious Diseases

Where does acetophenone that makes mosquitoes “fascinated” come from?

It turned out that it is a metabolite of microorganisms (genus) on the skin surface. Further studies have shown that infection by dengue virus and Zika virus inhibits an important immune factor in the skin-antibacterial peptides, thereby promoting habitation Such microorganisms on the body surface proliferate in large numbers.

This regulatory mechanism helped the research team find the inspiration for blocking the large-scale epidemic of mosquito-borne diseases – as long as the expression of antimicrobial peptides is restored, the growth of Bacillus dermoides will be controlled, the acetophenone will be reduced, and the mosquitoes will not be affected. Take special interest in the infected again.

In other words, the circulation of the virus will also be interrupted.

So, is there any drug that can achieve the above effect? After trial and error using a mouse model, isotretinoin, a vitamin A derivative, offers a glimmer of hope. When mice infected with dengue virus and Zika virus were fed isotretinoin, their expression of antimicrobial peptides returned to normal and the release of acetophenone was inhibited.

However, whether vitamin A drugs are equally effective in humans remains to be further verified. At present, the research team has started to prepare for the next stage of work. It is believed that in this difficult and difficult “human-mosquito war”, human beings will win the final victory.