Dengue and Chikungunya Outbreaks Severely Impacting Hong Kong, Pakistan, and India

With so much of the world focusing on Zika virus in the Americas and Southeast Asia, it’s easy to forget that there are other mosquito-borne viruses causing serious public health problems globally—namely, Dengue fever and Chikungunya.

According to press reports, Hong Kong has identified 4 cases of locally transmitted Dengue fever so far this year, all since the beginning of August. All 4 of the patients live on Hong Kong Island, raising fears of a potential outbreak there.

In July, officials with the city’s Food and Environmental Hygiene Department warned residents that the local population of Aedes albopictus mosquitoes, which carry both Dengue and Zika virus, had reached “alert levels” in eight districts, and that overall it had reached an all-time high. As a result, the Hong Kong government stepped up surveillance protocols as well as larvicide spraying programs in an attempt to control the mosquito population.

Local residents were also advised against travel to areas where Dengue is a persistent threat, such as Pakistan and India. In Pakistan’s largest city, Karachi, more than 150 people have been hospitalized with Dengue fever so far this mosquito season. Many cases have reportedly progressed to Dengue hemorrhagic fever, and thus far four individuals have died as a result. Last year, across Pakistan, where vaccines against the virus are unavailable, more than 1,400 cases of Dengue fever were reported, with 40 fatalities.

The news is all the more troubling given new findings on the safety of Dengvaxia, a Dengue vaccine manufactured by Sanofi-Pasteur. In recent Phase III trials, conducted in Southeast Asia and Latin America, the vaccine was initially able to reduce the incidence of infection by 60% and the number of hospitalizations due to infection by 80%. However, researchers observed that many of those vaccinated later developed severe Dengue. Isabel Rodriguez-Barraquer, MD, a research associate at the Johns Hopkins University’s Bloomberg School of Public Health and one of the study’s co-authors, told Voice of America that she and her colleagues believe that vaccination essentially “acts like [a] first [Dengue] infection.” It has long been known that those who have been infected with Dengue once typically have more severe illness if they are infected again.

Meanwhile, in Delhi, officials have reported a marked increase in the incidence of Chikungunya in the city in recent weeks. Through September 17, more than 2,600 cases of the mosquito-borne virus had been reported in the Indian capital; however, nearly 1,600 of these cases were confirmed during the week of September 11-17, leading to a 150% increase in overall incidence. At least 12 deaths have been attributed to Chikungunya in Delhi alone. The city has also been dealing with a Dengue outbreak, with more than 1,600 cases of that virus reported during the current mosquito season.

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.