Dengue fever cases, countermeasures surge in Southeast Asia and beyond
Dengue fever is hitting Southeast Asia in force in 2019, according to the World Health Organization (WHO) and health authorities in the region.
More than 670,000 people have been infected with the disease and more than 1,800 have died from the infection through early September 2019 in Southeast Asia, according to Agence France-Presse. Cases have more than doubled in the majority of countries in the region where the disease is endemic, the wire service reported.
Public health officials, including members of militaries, across the broader Indo-Pacific region and the world are working together to prevent the spread of the disease. Various health programs and partnerships are implementing improved strategic plans, guidelines and remediation activities, and enhancing dengue control and prevention, including integrated vector management. Teams of public and private researchers continue to cooperate on developing effective vaccines and other biological approaches to control.
Philippine officials reported more than 1,000 deaths and 250,000 total cases from dengue fever through early September 2019. A national dengue epidemic was declared in August 2019 to mobilize public assistance for relief, according to media reports.
Bangladesh reported more than 50,000 cases for August 2019 alone, more than the total reported for the country from 2000 to 2018. Bangladeshi officials reported more than 100,000 cases and 58 deaths for the first eight months of 2019, the Outbreak News Today website reported.
“Since we started keeping record of dengue cases, which is from 2000, this is the worst dengue outbreak we have seen in Bangladesh,” Ayesha Akhter, assistant director at Bangladesh’s Directorate General of Health Services, told CNN.
Vietnam reported more than 124,000 cases and 15 deaths through August 2019, more than triple for the same period in 2018, reported. Meanwhile, Malaysia reported more than 85,000 cases and 121 deaths through mid-August 2019, nearly double the numbers of the previous year, Similarly, Thailand’s Bureau of Epidemiology reported more than 44,500 cases of dengue fever and 62 deaths through early July 2019, the highest number in five years, according to the Thai PBS World website.
Hong Kong, India, Indonesia, Laos, Maldives, Nepal, Singapore, Sri Lanka, Taiwan, Timor-Leste as well as various Pacific island nations, from Cook Islands to Tuvalu and Vanuatu, are also seeing significant outbreaks in 2019, according to the U.S. Indo-Pacific Command Surgeon’s Office.
Dengue, a viral infection transmitted by the bite of an infected mosquito, comes in four different but related strains that can affect infants, children and adults. Symptoms can include high fevers, severe headaches, eye, muscle and joint pains, lingering weakness, rash and bleeding, the Surgeon’s Office said.
Severe forms of the disease, including dengue hemorrhagic fever and dengue shock syndrome, claim about 25,000 lives worldwide annually, The New York Timesnewspaper reported. Although there is no treatment or cure for dengue, the fatality rate is less than 1% because of early detection and access to medical care, WHO said.
The recent surge in dengue cases is due in large part to higher temperatures enabling mosquitoes to live in larger expanses of the globe and a new strain of the virus that is transmitted rapidly in populations that don’t have immunity, many experts believe. Other factors, such as increased air travel and the increased use of plastics, also play a role.
“The major contributing factor is poor environmental cleanliness. Abundant man-made containers provide places for the Aedes mosquito to breed and increase the spread of the dengue virus,” Malaysian Health Ministry Director-General Noor Hisham Abdullah told The Straits Timesnewspaper, adding that littering contributes to the problem.
Governments in the region responded to the outbreaks by employing measures from increased surveillance to stepping up fogging and removal of mosquito breeding sites. (Pictured: A worker fumigates a residential area to prevent the spread of the dengue virus and other mosquito-borne diseases in Kathmandu, Nepal, in September 2019).
Various multistakeholder and multipronged cooperative efforts have been launched in the past decade to suppress dengue outbreaks. The Association of Southeast Asian Nations (ASEAN), for example, in conjunction with WHO, international and local partners and academics, have initiated efforts to mobilize dengue education, prevention and control from the annual ASEAN Dengue Day campaign, started in 2011, to regional workshops on mosquito suppression technologies. Worldwide, researchers have been working on vaccines for more than 80 years, but a safe and effective dengue vaccine remains elusive.
A French company, Sanofi Pasteur, has developed a live attenuated vaccine known as Dengvaxia that has been licensed since 2015 in 19 countries, including the United States, and endemic parts of Europe such as the Caribbean islands of Martinique and Guadeloupe. WHO recommends it only for adults with a history of infection with the virus. The Philippines banned the vaccine in December 2017 after at least 14 children died after 800,000 were vaccinated with the drug in 2016 and 2017, Philippine health officials said.
At least seven other candidate dengue vaccines are in various stages of clinical trials worldwide. The U.S. Walter Reed Army Institute of Research and the Armed Forces Research Institute of Medical Sciences, for example, are testing several in Southeast Asia in partnership with other government agencies and industry. Indian vaccine producers are testing yet another vaccine that was developed by the U.S. National Institutes of Health.
The World Mosquito Program is testing a new approach to controlling the spread of the dengue virus that entails injecting mosquitos with bacteria, called wolbachia, that sharply reduce the likelihood of transmission of dengue and other mosquito-borne illnesses such as Zika and yellow fever to humans. The wolbachia-carrying mosquitoes are then introduced into the wild to reproduce. Their offspring have a much smaller chance of transmitting the viruses to humans.
The approach has been tested in nine countries, including Vietnam, where it reduced the infection rate by 86% in the region where the mosquitos were released, Agence France-Presse reported.
“We have seen a significant drop in cases” from this experiment, Nguyen Binh Nguyen, a project coordinator in Vietnam, told Agence France-Presse in September 2019.
More than 128 countries, including China and the United States, are affected by dengue, which is the most widespread mosquito-borne illness worldwide with an average of about 390 million dengue infections occurring each year and nearly a quarter manifesting clinically with some form of the disease, with the majority occurring in Latin America and Asia, according to the International Research Consortium on Dengue Risk Assessment, Management and Surveillance.