- by Alison Booth

2015: deadly dengue outbreaks across Asia

Dengue fever victims

Image courtesy of IFRC

Hospitals across Asia struggle against soaring dengue cases

Malaysia, the Philippines, Thailand, Taiwan, Vietnam and India are some of the worst hit countries. According to the World Health Organization, Malaysia reported more than 107,000 cases and more than 293 deaths as of 21st November, up nearly 18% from 2014. The Philippines, meanwhile, reported more than 142,000 cases and 411 deaths as of October 31st, an almost 50% rise in cases compared with 2014. And Vietnam reported 58,633 cases and 42 deaths up to the end of October – a sharp rise in close to 19,000 cases in the past month. Meanwhile, Outbreak News Today reports 195 deaths in Taiwan.

India has been hit hard too. Extended warm weather has led to more than 90,000 cases as of late November, more than doubling the around 40,500 cases the country saw during the whole of 2014. New Delhi and Punjab are worst affected, with New Delhi facing its worst dengue outbreak in almost two decades. Hospitals in the capital are being asked to increase dengue bed numbers as thousands flock to get tested for the disease, according to Firstpost.

Publicity raises awareness – and fear

In Thailand, 123,168 have been infected so far this year, according to Karen News. Like New Delhi, it is the worst outbreak for more than 20 years. The Bangkok Post reports that those infected include popular actor Thrisadee “Por” Sahawong. Publicising his case has had its pros and its cons: on the upside, it shows no one is immune to the disease; on the downside, it’s creating a sense of panic as people strive to understand the facts.

Dengue has been badly overlooked by Thai people. They simply don’t know what the symptoms are, how the virus is spread and the preventive measures they can take today – along with those that might be available in the future, including vaccination.

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Understanding dengue

One key obstacle in the fight against dengue is a global lack of understanding about the tropical disease and how it spreads. Below are some interesting facts that might help:

Dengue comes in four different serotypes

According to the Centers for Disease Control and Prevention in the US, dengue is caused by any of four closely related serotypes of the dengue virus: DEN-1, DEN-2, DEN-3 and DEN-4.

Infection with one serotype does not protect you against infection from the others. In fact it has quite to opposite effect: multiple infections from different serotypes put you at greater risk for deadly severe dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS).

Asymptomatic people can pass dengue to mosquitoes

Three-quarters of people who catch dengue have few or no symptoms. Despite being asymptomatic, these people may play a key role in the dengue transmission cycle. The cycle starts with a mosquito catching the virus from an infected person. Mosquitoes are more likely to come in contact with infected people who are asymptomatic and going about their normal daily routine than people who are sick and bed-ridden or hospitalized when they catch dengue.

Research at the Institut Pasteur in Cambodia, the Institut Pasteur in Paris and the French National Centre for Scientific Research (CNRS) has shown that people with no clinical signs of dengue can pass the virus onto mosquitoes. “People with few or no symptoms – in other words the majority of those infected by dengue – may actually be contributing to the spread of the virus without realising it,” Louis Lambrechts, a CNRS scientist in charge of the Insect-Virus Interactions Group at the Institut Pasteur in Paris, told Infection Control Today.

Climate impacts dengue transmission

Many different factors influence the dynamics of dengue transmission; climate being one. Mosquitoes thrive in tropical climates: hot temperatures increase the survival and development rates of mosquito eggs and the female mosquitoes’ tendency to bite, and reduce the time it takes for dengue to develop within the mosquito; humidity improves adult mosquitoes’ and eggs’ chances of survival.

Unusually hot weather has caused an increase in dengue cases [in Taiwan], the Centres for Disease Control Taiwan told The Straits Times in September. “This year saw temperatures in Tainan and (the southern region of) Kaohsiung at their highest in 30 years,” Mr Chuang Jen-hsiang, CDC’s deputy director said.

Why we are all responsible

Fighting dengue is a communal responsibility. Governments and local authorities can only do so much to keep areas free from mosquito breeding grounds. Malaysian Health Minister Datuk Seri Dr S.Subramaniam explained why the public also has a role to play in helping combat the disease in an interview with the New Strait Times: “We can take various actions to fight dengue but if the public continue to litter and dump rubbish from the window of their apartment then all the efforts would be wasted.”

We spoke to Deepak Gunti, state entomologist with India’s Integrated Disease Surveillance Programme (IDSP) and Vector-borne Disease Control Programme (NVBDCP). He highlighted the importance of eliminating the vector’s ability to breed in the home. “The mosquito will breed in the standing water in our houses – in a plant pot or a cooler,” he explains. “We have to educate people to reduce the number of places where they can breed.”

We clearly need to help people learn about dengue. Will you help us raise awareness about the disease and how to prevent it?