Summary of Key Points
This year, people are feeling that mosquitoes have arrived earlier and bitten more aggressively. It's not that the mosquitoes have “evolved,” but rather that the main culprits for the bites are the “Aedes albopictus” mosquitoes from the south. These mosquitoes are rapidly spreading in the north, with climate change being the primary driving factor. Not only do their bites cause larger, more itchy swellings, but they can also transmit dangerous diseases such as dengue fever. Moreover, they are becoming increasingly resistant to common mosquito coils and insecticides. As climate continues to warm, the mosquito problem is likely to worsen.
Detailed Analysis
1. The Mosquitoes Biting You Are Not “Old Friends” – They’re “Migrating” Insects from the South
In previous years, the mosquitoes in the north were mainly the Culex mosquitoes, which are small and cause mild bites. This year, many of the mosquitoes are Aedes albopictus, also known as “tiger mosquitoes,” which are larger and more aggressive. They bite during the day, and the swellings they leave are red, swollen, and itchy for a week.
Why have the tiger mosquitoes successfully migrated north? Climate change is the key factor: in the past, winters in the north were cold (temperatures below -5°C), making it impossible for the tiger mosquito eggs to survive. Now, with temperatures in North China and Northeast China rising by more than 0.3°C every decade, winters are less cold, and there is sufficient rainfall, allowing the tiger mosquitoes to reproduce steadily. For example, in Dongcheng District of Beijing, the proportion of tiger mosquitoes increased from less than 30% ten years ago to 43% in 2023, and they are almost becoming the dominant species in the area. The earlier spring warming has also caused them to become active earlier; they used to emerge in May or June, but this year, they have started biting in March or April.
2. Tiger Mosquito Bites Are Not Only Itchy – They Can Be Deadly
The danger posed by tiger mosquitoes goes beyond the discomfort of the bites. They are the primary carriers of dengue fever, also known as “breakbone fever.” Symptoms include high fever and bone pain as if the bones have been broken. There is no specific treatment for dengue fever, and patients can only rely on their bodies to fight the infection.
Data shows that from 2019 to 2024, there were a total of 67,000 dengue fever cases nationwide, with each major outbreak lasting longer than the previous one (the 2024 outbreak lasted 238 days). The number of cases in the first five months of this year increased by 88.5% compared to the same period last year, and the proportion of cases spreading across provinces rose from 2.36% to 6.34%. In addition to dengue fever, they can also transmit chikungunya fever (which occurred in Guangdong last year). These viruses can seriously affect a person’s health.
3. Are Mosquito Coils and Repellents No Longer Effective? Mosquitoes Have Developed Resistance
The perception that mosquito coils are ineffective is not an illusion – mosquitoes have developed resistance to common insecticides. The mosquito coils and aerosols we use contain pyrethroids, which are inexpensive and relatively safe. However, prolonged use has made mosquitoes resistant to these substances. In 2020, monitoring in 13 provinces across the country showed that almost all tiger mosquitoes were resistant to pyrethroids. In Guangdong, in 2023, 85% of the mosquito populations were resistant to pyrethroids, and the resistance to organophosphates was as high as 92%. Other insecticides either pose higher risks (such as organophosphates, which cannot be used at home) or are less effective. This creates a cycle where both humans and mosquitoes constantly upgrade their defenses, with potential harm to humans if used excessively (e.g., inhaling excessive insecticide can irritate the respiratory system).
4. Will Mosquitoes Become Even More Aggressive in the Future?
Research predicts that by 2050, the average annual temperature nationwide will be 2.17°C higher than in 2000, and the areas affected by tiger mosquitoes will cover nearly all densely populated regions, with the number of affected people increasing from 960 million to 1.2 billion (85% of the total population). For every 1°C increase in temperature, the number of dengue fever cases in Guangzhou is expected to rise by 66.7%. However, if temperatures rise by more than 2°C, the mosquitoes may become too weak due to the heat. For now, this scenario is not yet a reality.
Even worse, the Aedes aegypti mosquito, another carrier of dengue fever, may move north and west, potentially expanding the range of outbreaks.
5. What Can Ordinary People Do?
There is no perfect solution to mosquito problems, so a combination of approaches is necessary:
- Physical Protection: Wear long sleeves and pants, use mosquito nets, and set the air conditioning to a lower temperature (mosquitoes are less active in cooler environments).
- Chemical Protection: Use different types of mosquito repellents (such as DEET or picaridin) and avoid using the same one for extended periods.
- Emergency Relief: Apply antipruritic creams after bites. While scratching may provide temporary relief, it’s better than scratching the skin raw.
In conclusion, as mosquitoes become more aggressive, we can only take temporary measures and hope for more effective solutions in the future.