Dengue Fever (update July 2023)
Nepal had an outbreak of dengue in 2022 with 54,784 reported dengue cases and 88 deaths, cases detected with maximum number of cases occurring in Kathmandu valley.1 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.
Dengue fever is a disease of the tropics and subtropics with approximately 400 million people affected each year. It is caused by any one of the four related viruses transmitted by day- biting aedes mosquitoes. Serotypes 1, 2 and 3 of dengue viruses were found in the 2022 outbreak in Nepal.2 The disease is characterized by sudden onset of high fever, pain behind the eyes, headache, backache, joint and muscle pains. 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. A small number of patients with dengue will develop bleeding and other complications who will need to be hospitalized. No specific treatment is available and spontaneous recovery is the rule.
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 or Picaridin 20%. Staying inside screened/air conditioned accommodation is an effective way to avoid being bitten by mosquitoes. The first Dengue fever vaccine (Dengvaxia) that was licensed for use in 20 countries around the world, was found to cause severe disease in persons with no prior immunity to dengue. WHO has recommended that it only be used in individuals after confirming prior dengue infection. Another vaccine QDenga by Takeda can be used in all individuals without accounting for seropositivity. This vaccine is currently approved in Europe and many other countries across the globe. It is yet to get approval by the US CDC. Both these vaccines are not available in Nepal at present.
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 as cases are increasing this year too. 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.
- Epidemiology and Disease Control Division. Situation update of Dengue 2023 (As of July 15, 2023). 2023. https://edcd.gov.np/public/uploads/news/pdf/64b405ebf1899.pdf
- Amatya B, Schwartz E, Biber A, Erster O, Lustig Y, Pradhan R, Khadka B, Pandey P. Dengue serotype characterization during the 2022 dengue epidemic in Kathmandu, Nepal. Journal of Travel Medicine. 2023. 10.1093/jtm/taad034 https://doi.org/10.1093/jtm/taad034