The four-flavoured virus: Dengue in Vietnam

Dengue fever has nothing like the level of global recognition achieved by malaria, and yet the dengue virus, transmitted by Aedes aegypti mosquitoes, infects up to 100 million people a year worldwide.

‘The WHO sees dengue as a neglected tropical disease’, says Professor Cameron Simmons, who heads a research group on the disease at the Oxford University Clinical Research Unit (OUCRU) in Vietnam. ‘Compared with something like malaria, dengue does not kill many people. But it causes a lot of sickness, and puts a strain on healthcare resources and on families themselves.’ OUCRU works closely with the Hospital for Tropical Diseases in Ho Chi Minh City, and with a network of hospitals throughout the country. ‘We invest heavily in support for local students, post docs and clinical trainees, because we know that’s the best way to do science in this setting’, says Professor Simmons.

Vietnam’s hospitals see 50,000-100,000 cases of dengue per year, but he thinks the country’s overall total is probably five to ten times higher. The symptoms are high fever, headache, and muscle aches and pains. Dengue shock syndrome is a life-threatening complication that can occur in children. ‘10 per cent of children with dengue shock syndrome used to die’, says Dr Simmons. ‘Now, with good patient management, it’s down to 1 per cent.’

Good management is all that is on offer: there is no drug available to treat the virus, and no vaccine to prevent it. A vaccine would be the best way to reduce the global burden, but dengue is peculiarly complicated to deal with. There are four known strains, or serotypes, and a vaccine would have to include them all. ‘The amazing thing is that infection with one serotype makes you immune to that serotype for the rest of your life,’ says Dr Simmons, ‘but you can still get the others, and the complications can be worse.’

In the meantime OUCRU has worked to improve the supportive management of dengue, and developed laboratory tests that might predict which patients will develop complications. Drug therapies are also important. ‘We are working to develop drugs to reduce the length and severity of symptoms’, says Dr Simmons. ‘We’ve done a number of early phase clinical trials, both academic and industry led.’ He points out that there is growing interest in dengue among pharmaceutical companies as it is also a huge problem for middle-income countries such as Brazil.

The OUCRU researchers continue to gather information about the underlying biology of the disease. ‘We are understanding what parts of the immune response are important in immunity, and in blocking transmission by mosquitoes’, says Professor Simmons. ‘If we can understand pathogenesis better, we can be more rational with therapeutic interventions.’ They are also collaborating with Australian researchers on biological control of the mosquito population, and recently recruited the 5000th baby in an epidemiological study that will follow the natural history of the disease in Ho Chi Minh City and a rural village in the Mekong delta.

‘I trained as microbiologist and immunologist,’ says Dr Simmons, ‘but now we try to avoid -ologies. I just say I work on dengue.’