Nepal’s climate is broadly subtropical, characterised by large seasonal variations in temperature, rainfall and humidity. Dengue fever and complications arising from dengue are widespread in such subtropical and tropical regions of the world. With global warming, dengue-carrying mosquitoes are able to survive in more areas, leading to a bigger population at risk. Dengue fever is thus very common in South Asia. Frequent rains, the tropical environment, unplanned urbanisation, vacant houses, and improper waste disposal all leave lots of room for mosquito breeding.

The aedes mosquito, which carries dengue, is mostly confined to urban areas, where they breed in the relatively clean water found in storage jars, discarded tyres and tin cans. The eggs of the aedes mosquito can live for 9-12 months in dry conditions. Once conditions become appropriate, they hatch. Female aedes aegypti mosquitoes need to suck blood from lots of people to complete one single meal. Such feeding habits rapidly increase the incidence of infection.

Signs and symptoms

The initial symptoms of dengue fever resemble undifferentiated viral fever. Symptoms include high grade fever, severe headache, retro-orbital pain, myalgia and arthralgia, nausea, vomiting and rashes. Fever is usually between 39 to 40 degree Celsius and may be biphasic, lasting for three to seven days. Diffuse erythema and fleeting eruptions may be observed in the initial days of fever. In the convalescent period, normal skin surrounded by erythema—a redness of the skin due to increased blood flow—may be observed. The clinical course of dengue fever varies between individuals. But the febrile phase lasts for an average of five days. Fever persisting for more than six days should be investigated for other causes. Bradycardia, or “abnormally slow heart action”, may also be present.

The danger signs of dengue fever include persistent vomiting, abdominal pain and tenderness, inability to eat, bleeding from any site, severe lethargy, inability to walk, restlessness, build-up of fluid in the abdomen, water in the lungs, narrow pulse pressure, hypotension and tender enlarged liver, and rapidly falling platelet count. Skin hemorrhages may also be present. Severe plasma leakage can result in circulatory disturbances and shock, which can manifest as severe acute abdominal pain, irritability, restlessness and inability to sleep, especially in children. Bleeding is usually manifested when shock is prolonged. It can also occur spontaneously when nonsteroidal anti-inflammatory drugs and steroids are used.

Dengue viral infection, however, can be asymptomatic. After the incubation period, the disease has three clinical phases—febrile phase, critical phase and recovery phase. Depending on its severity, patients can present undifferentiated fever, dengue fever with danger signs, or severe dengue. The febrile phase usually lasts two to seven days. There may be pharyngitis, neurological impairment and febrile seizures. A positive tourniquet test can identify the presence of dengue. But there are no clinical features to predict whether a patient may deteriorate into severe disease.

The critical phase is the most important period that needs to be identified. A failure to detect and treat this phase may lead to severe dengue, causing death. The critical phase begins when the fever starts decreasing or when patient becomes afebrile. This lasts for 24-48 hours. During this period, plasma leakage occurs.

The recovery face lasts for two to three days after the critical phase. During this phase, edema starts to resolve and fluid returns to the intravascular space. The patient’s general wellbeing and appetite improves.

There could be severe itching, especially on the palms and soles of the feet. Diuresis sets in, the ratio of red blood cells in the blood falls to normal levels and the number of platelets increases.

Preventing dengue

The most important aspect of prevention is to avoid being bitten by mosquitoes, by covering up where practical, and through the use of the insect repellent DEET in 30 percent strength. Staying inside screened and air conditioned accommodations are an effective way to avoid being bitten by mosquitoes. Wearing neutral-coloured (beige, light grey) clothing and if possible, long-sleeved, breathable garments is recommended.

Furthermore, water containers around dwellings should be gotten rid of or covered. Doors and window screens need to work properly.

A vaccine is available for people living in some dengue-ridden countries, but it is not commercially available. The first dengue fever vaccine (Dengvaxia), which was licenced for use in 19 countries around the world in 2015, has been found to cause severe disease in persons who have no prior immunity to dengue. The World Health Organisation has recommended that this vaccine only be used after confirming prior dengue infection in individuals. No specific treatment is available and spontaneous recovery is the rule.

There are regular dengue epidemics in the Maldives, India, Sri Lanka, Thailand, Malaysia, Singapore, and Indonesia. The risk of dengue in Nepal is lower than these other countries. In South East Asia, dengue is transmitted all year round, but occurs mainly during the wet summer months and the post-monsoon.  

Dengue burden in Nepal

Dengue cases in Nepal are exacerbated by the poor availability of medical and diagnostic facilities, inadequate mosquito control and climatic conditions that favour vector expansion. Dengue infections are more common in the Tarai region but the vector has adapted to the extremes of warm and cold weather, resulting in the occurrence of dengue cases throughout the year in Nepal.

Dengue fever cases have been reported every year from the Tarai since its emergence in 2004. The first significant outbreak of dengue in Nepal was reported in 2006 when around 35 cases occurred. There were two large outbreaks of dengue in Nepal, in 2010 and 2013, with 917 con?rmed cases and ?ve deaths, and 642 con?rmed cases, respectively. The Epidemiology and Disease Control Division (EDCD) under the Ministry of Health reported 1,615 dengue cases in 32 districts during another outbreak in 2016.

This year, dengue was reported in more than 1,500 people across the country. The highest number of cases was in Chitwan, followed by Jhapa, Rupandehi and Makwanpur. Dengue outbreaks peaked during August to October, corresponding with the tail end of monsoon season, and subsided around the last week of November.

Nepal is a poor country and Kathmandu has a high level of poverty, featuring a considerable amount of sub-standard housing and water hygiene.

Poor health, social and economic infrastructures of Nepal in general and Kathmandu in particular, along with an increasing average temperature, are among the factors leading to the increased spread and incidence of dengue into highland areas. Occurrences over the past 14 years of multiple circulating serotypes, along with an overall increasing burden of dengue cases, suggests that this number is likely to rise in Nepal in the coming years.

Each district has one district hospital (governmental public hospital), and numerous private/non-governmental hospitals, nursing homes and medical colleges. Public hospitals commonly have their own laboratory for routine diagnosis but lack a molecular laboratory for the confirmation of pathogens. Private hospitals too rarely have molecular diagnosis and thus, the diagnosis can be very costly.

Laboratories that provide reliable confirmation of dengue infection are few and are mostly based in Kathmandu. The only tropical disease hospital, Shukraraj Tropical and Infectious Disease Hospital, is based in Kathmandu.

The majority of Nepal’s population and specifically those most at risk have little to no access to these facilities. However, commercial kits for diagnosis have recently been made available to many hospitals through the Epidemiology and Disease Control Division under the Ministry of Health.

If more steps are not taken to limit the spread and incidence of this disease in Nepal, the number of infections and resulting complications are only likely to rise in the coming days.

- Banjade is a medical officer at Ministry of Health, Maldives