Summary of Key Points
In the summer of 2026, there was a surge in cases of mosquito-borne diseases such as dengue and chikungunya (with dengue cases increasing by 88.5% year-on-year). The prevention and control efforts faced several major challenges: mosquito resistance to pesticides, difficulty in eliminating breeding sites, lack of public participation, and high costs associated with pest control measures. Experts argue that relying solely on large-scale chemical disinfection does not address the root causes of the problem. The key lies in everyone taking action to clean up standing water, combined with scientific use of pesticides, legal regulations, and environmentally friendly prevention methods to cut off the transmission chain at its source.
1. Surge in Cases: A Triple Threat from Weather, Human Mobility, and the Environment
Why has the number of cases increased so sharply this year? There are three main reasons:
- Weather Conditions Favour Mosquito Reproduction: Hot and rainy summers create ideal conditions for the Aedes albopictus mosquitoes (the type that transmits these diseases). The larvae in standing water can mature into biting adults within a week, leading to a rapid increase in their population.
- Cross-border Travel and Virus Spread: Summer travel and events like the Canton Fair facilitate the introduction of viruses from overseas regions (such as Southeast Asia and Africa), with provinces along the border, like Guangdong and Zhejiang, being particularly affected.
- Urban Environments That Contribute to Mosquito Survival: Pools at construction sites, flower pot trays on balconies, old tires, and water collection dishes from air conditioners all provide breeding grounds for mosquitoes. As urbanization progresses, these hidden sources of standing water become more common, allowing mosquitoes to multiply more easily.
Data Highlights: Cases have been reported in 28 provinces across the country in the first five months, with Guangdong accounting for the majority of local cases (15 dengue and 36 chikungunya). Cluster outbreaks have also occurred in communities within the Pearl River Delta region.
2. Chemical Disinfection Faces Limitations: Resistance to Pesticides and High Costs
Many areas rely on spraying pesticides to control mosquitoes, but the effectiveness is diminishing:
- Mosquitoes Developing Resistance: Monitoring in Guangdong and Zhejiang shows that Aedes albopictus mosquitoes have developed resistance to common insecticides (such as deltamethrin) by hundreds to thousands of times. This means that what used to kill 100 mosquitoes with 1 milliliter of pesticide now requires 1,000 milliliters. Even some previously considered "safe" insecticides, like dichlorvos, are no longer effective against certain mosquito strains.
- High Costs with Limited Benefits: The daily wage for frontline disinfection workers in Guangzhou is around three to four hundred yuan, and a single application only kills the adult mosquitoes present; the larvae hiding in green spaces or standing water remain unaffected. By the next day, new larvae emerge, rendering the effort futile.
Experts suggest that spraying pesticides is not ineffective, but it must be done strategically, with regular monitoring of mosquito resistance and rotation of different chemicals to prevent them from developing a resistance pattern.
3. Cleaning Breeding Sites: Lack of Public Participation and Difficulties in Managing Public Areas
Aedes albopictus mosquitoes have a flight range of about 100 meters, so most community outbreaks originate from standing water near residents' homes. However, why is it so difficult to clean up these breeding sites?
- Residents Finding It Troublesome: Many people are aware of the need to remove standing water, but they often put empty bottles and flower pot trays back in place after cleaning, allowing rainwater to accumulate again, creating new breeding grounds.
- Hidden Breeding Areas in Public Spaces: Low-lying areas at construction sites, maintenance wells for municipal pipelines, and ornamental water features in green spaces are difficult to monitor and manage effectively, leading to the persistent presence of mosquito breeding grounds. Urban planning often fails to account for mosquito prevention needs.
Comparison with Hong Kong: Hong Kong has strict regulations and health inspectors who can enter homes to check for standing water and impose fines for non-compliance (up to tens of thousands of Hong Kong dollars). As a result, residents are more proactive in maintaining cleanliness. During the 2025 outbreak in Foshan, there were only 9 local cases compared to 29,497 in mainland China, demonstrating the effectiveness of legal enforcement.
4. A Comprehensive Approach: Community Participation and Legal Regulation for Long-Term Prevention
Experts agree that the focus should shift from temporary measures to long-term solutions:
- Community-Mediated Clean-up Efforts: Regularly cleaning standing water at home (e.g., in flower pots, buckets, and potted plants) can interrupt the mosquito breeding cycle. During outbreaks, continuous clean-ups for two to three days, combined with short-term disinfection, can quickly reduce mosquito populations.
- Legal Enforcement to Promote Responsibility: By adopting Hong Kong's approach and establishing clear responsibilities for governments, organizations, and residents (e.g., fining those who do not clean up their own breeding sites or companies that neglect to manage their construction site waste), we can create a more effective prevention system.
- Technology and Collaboration: The use of smart monitoring devices (such as mosquito density sensors) and improved data sharing between health authorities, customs, and communities (e.g., information on travelers from abroad) can enhance the accuracy of prevention efforts.
In summary, while short-term chemical disinfection is necessary for emergencies, only by encouraging widespread participation in cleaning up standing water and enforcing legal regulations can we effectively control mosquito populations and navigate this summer's peak season.