British holidaymakers booked to travel to south-east Asia this winter have been warned to take precautions as a severe dengue outbreak spreads across the region.
The Philippines, Thailand, Indonesia, Vietnam, Laos, Singapore and Sri Lanka have all reported significant increases in cases of the disease, which is transmitted by the Aedes mosquito. This week, Nepal became the latest country to be hit by the unprecedented outbreak, in which more than 8,000 people have been hospitalised.
The World Health Organisation’s Western Pacific office has called on countries in the region to raise awareness of the disease and improve patient treatment. The warnings are primarily directed at the domestic populations of countries in the region but also apply to the millions of tourists who visit south-east Asia each year.
Health Protection Scotland, which maintains the travel health website fitfortravel (fitfortravel.nhs.uk), has issued updated advice on dengue for Singapore and Sri Lanka. The agency said that more than 35,000 cases had been reported by early August in Sri Lanka, a country attempting to woo back tourists following the Easter Sunday bombings.
The Foreign and Commonwealth Office also has advisories for dengue in place for Indonesia, the Philippines and Vietnam, where it has warned of “higher than normal infections” in the north of the country.
Dengue, or haemorrhagic fever, is a sometimes fatal viral infection transmitted by the Aedes mosquito. The illness is characterised by high fever, severe headaches, aching bones and red spots and rashes on the skin. Within a few days the illness usually resolves and serious complications are uncommon, however in between one and two per cent of cases dengue can progress to a more serious form, severe dengue, which can be fatal. There is no widely available vaccine or cure for the disease other than rest and plenty of fluids.
According to the WHO, dengue is the world’s most common mosquito-borne disease, infecting more than 380 million people a year and causing 25,000 deaths. Unlike malaria, dengue is common in densely-populated urban areas, where mosquitoes lay eggs in anything from the rims of used car tyres to flower pots and rain gutters.
Malaysia reported 81,635 dengue cases in the first seven months of this year, with 113 deaths. This compares to 80,600 cases and 147 deaths in the whole of 2018. The country’s health ministry has forecast that more than 150,000 cases will be recorded this year.
Last month the Philippines declared a national epidemic of dengue fever, the first time it has done so since 2000. More than 600 people have died from dengue in the Philippines this year while Singapore has recorded more than 9,000 cases of dengue in the first seven months of this year, five times higher than the figure for the whole of 2018 - and five people have died of the disease.
Experts at the University of Malaya in Kuala Lumpur say the increase is attributable to a combination of wetter and warmer weather. The Aedes mosquito is more active in hot weather while more rain creates the puddles and standing water in which mosquitoes can lay their eggs. Air travel is also thought to contribute to its spread.
The most effective approach is to avoid being bitten in the first place and travellers are advised to wear long sleeves and trousers where mosquitoes are present and apply insect repellent. Unlike malarial mosquitoes, the Aedes mosquito typically bites during the day.
The spike in dengue cases comes as medical authorities have also warned that malarial parasites in parts of south-east Asia have now developed resistance to the most commonly used prophylactic treatments. The WHO says that, after an unprecedented period of success in global malaria control, progress has now stalled and drug-resistant strains of malaria are on the rise in south-east Asia.
The Mahidol Oxford Tropical Medicine Research Unit in Thailand has described the disease as “getting close to untreatable”. The Lancet medical journal has reported that the most common form of treatment failed to cure the disease in 13 per cent of cases in northeastern Thailand, 38 per cent in western Cambodia, 73 per cent in northeast Cambodia and 47 per cent in southwest Vietnam.
Scientists believe it is possible that drug-resistant strains of malaria emerge in south-east Asia because antimalarials are widely and heavily used there. This puts pressure on strains to adapt and develop resistance.
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