Taiwan - Dengue fever prevention achievements in Kaohsiung City in 2014

Issues and Objectives

An analysis of dengue fever outbreaks in Kaohsiung City from 2007 to 2013 revealed that only 2010 and 2011 saw outbreaks with approximately 1,200 cases. In the other years, the number of confirmed cases ranged from 108 to 746. A dengue fever outbreak occurred in Kaohsiung City in 2014, with a cumulative total of 14,968 confirmed cases by December 31st of that year. This caused considerable public anxiety, and the corresponding prevention and control efforts incurred significant social costs. Dengue fever has become a major public health issue affecting public health and quality of life. This paper discusses the prevention and control achievements in Wanzi Village, Sanmin District, Kaohsiung City, the area most severely affected by the outbreak, hoping to provide a reference for future dengue fever prevention and control efforts.

---

Improvement Measures Taken

1. Phase 1 (early stage of the epidemic): Weeks 31 to 39 of 2014 (August to the end of September). A cluster outbreak occurred in Wan'ai Village in week 36. From week 37 to week 40, the Health Bureau carried out mandatory source elimination and chemical control work within a 75-meter radius of the cluster outbreak.
2. Phase Two (Peak of the Epidemic): Weeks 40 to 43 of 2014 (late September to mid-October). Weeks 40 to 43 were the peak of the epidemic in "Wanzi Village". Related prevention and control work was also concentrated in this phase, and a total of 1,558 households were covered by prevention and control work.
   • 167 cases were identified in Wanli Village. The Health Bureau completed the mandatory source elimination and chemical control work in the entire Wanli Village in 43 weeks.
   • This article identifies 72 cases. The Health Bureau will carry out mandatory source elimination and chemical control work within 150 meters and 100 meters of the cluster outbreak area in weeks 43 and 45, respectively.
   • 44 cases were confirmed in Wansheng Village, and the Health Bureau completed the prevention and control work in the entire village in 43 weeks.
   • 38 cases were confirmed in Wanzhong Village. The Health Bureau will carry out mandatory source elimination and chemical control work within a 150-meter radius of the cluster outbreak for 42 weeks.
   • 24 cases were confirmed in Wancheng Village. The Health Bureau carried out mandatory source elimination and chemical control work within a 100-meter radius of the cluster outbreak on week 43.
3. Phase 3 (End of the pandemic): Weeks 44 to 52 of 2014 (late October to late December)
   • 56 cases were confirmed in Wanfu Village. The Health Bureau carried out two 150-meter-wide prevention and control operations within 45 weeks to complete the mandatory source elimination and chemical control work in the entire village.
   • 27 cases were confirmed in Wanzili. The Health Bureau will carry out mandatory source elimination and chemical control work within a 150-meter radius of the cluster outbreak for 46 weeks.
   • As of week 49, a total of 36 cases had been identified in Wanhua Village. In week 44, the Health Bureau implemented mandatory source elimination and chemical control measures within a 150-meter radius of the cluster outbreak.

---

Results

In 2014, the highest number of cases in the "Wanzi Village" cluster in Sanmin District was in Wanli Village. A cluster outbreak rapidly emerged in Wanli Village starting in week 40 and spread to the surrounding Benben and Wansheng Villages. The average incubation period in the early stages of the outbreak was 3.7 days, exceeding the Centers for Disease Control's recommendation of less than 3 days. Prevention and control measures may have been one reason for the rapid spread of the outbreak. In Kaohsiung City, the average incubation period between weeks 31 and 52 ranged from 2.8 to 4.1 days. The incubation period in the first week of the "Wanzi Village" outbreak reached 8 days, while the first confirmed case in the most severely affected Wanli Village had an incubation period of 6 days. This case required three medical visits before being reported, potentially leading to community spread and increasing the risk of transmission. The excessively long incubation period has two causes: insufficient public awareness, with many people only seeking medical attention after developing symptoms; and insufficient awareness among medical institutions regarding reporting. Therefore, it is essential to strengthen the monitoring of the epidemic in its early stages and promptly inform medical institutions and the public about the epidemic. Medical institutions should also report any suspected dengue fever cases immediately so that health authorities can initiate prevention and control measures in a timely manner.

Since 2015, the widespread use of rapid diagnostic reagents for dengue NS1 (non-structural protein 1 of dengue virus) antigen has assisted clinicians in rapidly diagnosing dengue fever, improving reporting timeliness, and helping health authorities to take timely prevention and control measures to avoid the spread of the epidemic. It also allows for early and appropriate clinical treatment of dengue-infected cases, preventing severe cases and deaths. In the "Wanzi Village" area of ​​Sanmin District, the peak occurred in week 42, with the number of cases increasing 2.1 times (165/78) compared to week 41. The peak lasted only one week, after which the epidemic began to decline, with the number of cases in week 43 being only 0.7 times (116/165) of week 42. The peak of the "Baozi Village" outbreak in Sanmin District occurred in week 44. The overall upward trend of the epidemic was relatively slow. The number of cases in week 44 increased by only 1.2 times (86/101) compared to week 43. The peak lasted for 3 weeks (weeks 44 to 46). The number of cases in week 47 was 0.6 times that of week 46 (61/101).

Comparing "Wanzi Village" and "Baozi Village" in Sanmin District, the outbreak in "Wanzi Village" occurred earlier and peaked quickly. Due to public health intervention, the peak lasted only a week before a significant decline. In contrast, the outbreak in "Baozi Village" peaked more slowly, and despite continuous prevention efforts, the peak lasted three weeks before declining. While dengue fever is influenced by various factors such as population characteristics, socioeconomic conditions, housing type, and climate, the effectiveness of public health intervention in controlling the outbreak is evident. However, years of experience in dengue fever prevention show that the speed at which the public eliminates breeding grounds is far slower than the speed at which residents create them. Public participation is essential for long-term dengue fever prevention. Therefore, the combination of dengue-related health education and administrative enforcement can enhance public awareness and vigilance regarding the epidemic. Dengue-related health education can encourage village chiefs and other community leaders to lead residents in improving their understanding of prevention and environmental awareness, and encouraging them to voluntarily reduce container usage. Furthermore, administrative penalties can raise public awareness of dengue fever outbreaks, leading to better dengue prevention and control efforts. These long-term measures can also be seen as adaptation strategies to strengthen public health and disease prevention systems in response to future climate change.

Glossary

Climate change risk assessment: Using effective assessment tools to understand the medium- and long-term impacts of climate change on various sectors, and to propose corresponding adaptation strategies and actions to reduce the risks brought about by climate change.

Case type:

Structural and physical options: engineering techniques or reinforcement of existing structures, integrated technology development

Social options: learning and exchanging disaster knowledge in the community, and developing and applying early warning information.

Institutional options: Establishing institutions at the economic, policy, and legal levels

---

References

Dengue fever prevention and control achievements in Kaohsiung City in 2014: Taking Wanzi Village, Sanmin District, Kaohsiung City as an example, Zhang Jinyu, Duan Yanchang, Lin Huizhen, et al., Epidemic report, Vol. 34, No. 11, June 5, 2018. DOI: 10.6524/EB.201806_34(11).0001

---

Reference Websites

---