icddr,b studies contribute to global dengue control and prevention efforts

icddr,b scientists are participating in an eight-country study aiming to identify simple methods to spot dengue infections, which are hard to diagnose from clinical symptoms alone and can be fatal if diagnosed too late.

The Aedes has distinctive black and white stripes. Photo: Airman Magazine/Brian Ferguson. CC BY-NC 2.0


Dengue, a viral infection spread by the infamous Aedes aegypti mosquito, is the fastest growing mosquito-borne disease in the world today, according to the World Health Organization (WHO). Since a large outbreak in 2000 in Bangladesh, cases have been regularly reported, including deaths from severe dengue. In 2016, the reported cases of dengue reached a nine-year high.

Dengue usually causes mild illness, but in some cases it can become more serious and potentially fatal. Preventing the disease from becoming severe largely depends on early detection and appropriate medical care. “This makes the new study aiming to improve clinical management of dengue very important,” says Dr Firoz Ahmed, an associate scientist at icddr,b and one of the investigators of the study published in BMC Infectious Diseases.

Unfortunately, the symptoms of dengue infection – such as fever, headaches and rashes – are shared with several illnesses, making diagnosis very difficult. In addition, it is not yet possible to predict which patients with dengue infections are likely to develop severe disease.

These are the key challenges the international project is tackling. More than 7000 patients have been enrolled in the study spanning eight countries. Patients with fever of unknown cause are being monitored for up to six days, and then visited a week later.

By following a large number of patients, the researchers hope to identify simple clinical signs or laboratory tests that distinguish dengue from other causes of fever, and could be used to identify those at risk of severe disease at an early stage. Use of such tests could ensure that patients with dengue receive the right treatment, and those at risk of severe disease are given special attention.

The study is also assessing the new World Health Organization (WHO) classification scheme for dengue in practice, and results from the study could be used to update theIntegrated Management of Childhood Illness (IMCI) algorithm for dengue-endemic countries.

“The laboratory investigation in Bangladesh is being conducted at icddr,b as part of this large-scale study in health facilities in eight countries across Asia and Latin America through an internal consortium of three uniquely capable organisations, icddr,b, James P Grant School of Public Health at BRAC University, and Shaheed Suhrawardy Medical College Hospital,” says Dr Ahmed. The work is being funded by a grant from the European Union to the International Research Consortium on Dengue Risk Assessment, Management and Surveillance.


Dengue prevention and public health

Dengue outbreaks are considered public health threats in the Asia-Pacific region, with reports of cases escalating during the monsoon season in South Asia.

The Aedes also spreads yellow fever, Zika, chikungunya. Photo: Airman Magazine/Brian Ferguson. CC BY-NC 2.0


Rainfall leading to stagnant water generally facilitates mosquito breeding. Dengue has been on the rise in Dhaka in this monsoon. A recent study on dengue led by icddr,b researcher Dr Emily Gurley found a correlation between increased rainfall in Dhaka and the number of dengue cases two months later. Data from 2010–14 revealed that 90% of cases occurred between June and November, highlighting the importance of being prepared for a surge of cases during peak months.

Prevention of dengue has traditionally focused on control of mosquito vectors. However, the first dengue vaccine was licensed in Mexico late in 2015 and other vaccines are in the pipeline, raising hopes that dengue will soon be a vaccine-preventable disease.

In early 2016, icddr,b began a clinical trial of a dengue vaccine developed by the US National Institutes of Health in collaboration with the University of Vermont (UVM) Vaccine Testing Center and the Johns Hopkins School of Public Health. In the first ever dengue vaccine clinical trial in the Indian subcontinent, a team led by icddr,b senior scientist Dr Rashidul Haque is assessing the new vaccine’s safety and immunogenicity – its ability to stimulate protective immune responses – in Bangladesh.

Dr Haque suggests that the ability to expand the icddr,b’s capacity to perform this double-blind placebo-controlled clinical trial will generate vital data on this new vaccine and its potential to control an important emerging infection. The vaccine has already been tested in a small-scale study in the USA, where it protected all 21 participants deliberately exposed to dengue virus.