Dengue fever is a disease of the tropics and subtropics with over 100 million people affected each year. It is caused by any one of the four related viruses transmitted by day biting aedes mosquitoes. It is a common illness in many Asian countries but has not been much of a problem in Nepal after a big outbreak in 2010, although cases have now been picked up in the Kathmandu valley. The aedes mosquitoes carrying dengue are mostly confined to urban areas where they breed in the relatively clean water found in storage jars, discarded tyres and tin cans. Because the mosquitoes bite during the day (especially late afternoon) as well as the night it makes it hard to avoid exposure. Once bitten by an infective mosquito a person will become sick within two to eight days.
The disease is characterized by sudden onset of high fever, pain behind the eyes, headache, backache, joint and muscle pains. The severity of the joint pains has led it to be named “break bone fever”. It is often accompanied by a rash that looks like a red flush on the back, chest and abdomen. Fever returns to normal within a week, but may leave a person feeling tired and slightly depressed for a few weeks afterwards.
The most important aspect of prevention is to avoid being bitten by mosquitoes, by covering up where practical, and by the use of insect repellent DEET in 30% strength. Staying inside screened/air conditioned accommodation is an effective way to avoid being bitten by mosquitoes. At present there is no vaccine against dengue fever. Any traveler arriving from an area where dengue is a problem and who develops a sudden fever and headache within a few days of arrival, dengue fever should be suspected. However, because dengue often exists in countries where other fever causing illnesses are present (malaria, typhoid), it is important to rule out other illnesses. No specific treatment is available and spontaneous recovery is the rule.
There are regular dengue epidemics in India, Sri Lanka, Thailand, Malaysia, Singapore, and Indonesia that are popular travel destinations. Nepal is no longer an exception with a small epidemic in 2010 and cases now occurring in the Kathmandu valley. In SE Asia, dengue is transmitted all year round, but occurs mainly during the summer wet months and post- monsoon. In India, dengue fever shows a marked seasonal pattern, with most travelers becoming exposed during late September and October after the seasonal rains have stopped.
Dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS).
These are complications of dengue fever that are mostly confined to the people that live in an area where dengue fever is a problem, causing death mainly to indigenous population. With the increasing incidence of dengue worldwide due to urbanization and failure of mosquito eradication campaigns, it is likely that these complications may become more common in the increasing number of travelers to dengue endemic countries. DHF is characterized by persistent vomiting, severe abdominal pain, leaky blood vessels causing fluid leakage inside the abdomen and pleural space as well as bleeding complications and low platelets. These patients require immediate hospitalization and supportive treatment.