Dengue and severe dengue

Dengue is a mosquito-borne viral infection common in warm, tropical climates. It is caused by any one of four closely related dengue viruses (called serotypes), which can lead to a broad spectrum of symptoms, including some that are extremely mild (unnoticeable) to those who may require medical intervention and hospitalization. In severe cases, fatalities can occur. There is no treatment for the infection itself, but the symptoms that a patient experiences can be managed.

In 2023, WHO graded dengue as a Grade 3 emergency after outbreaks increased in several countries. Dengue epidemics tend to have seasonal patterns, with transmission often peaking during and after rainy seasons. Several factors contribute to this increase, including high mosquito population levels, susceptibility to circulating serotypes, favourable air temperatures, precipitation and humidity, all of which affect the reproduction and feeding patterns of mosquito populations, as well as the dengue virus incubation period. Unplanned urbanization and climatic factors such as heat waves and high temperatures have increased the intensity, frequency, duration and distribution of dengue in recent years. Lack of sustained surveillance and control interventions as well as staff are some of the other challenges. Absence of an integrated programmatic approach continues to affect countries.

Dengue is a self-limiting febrile illness with symptoms ranging from extremely mild (asymptomatic) to severe. Symptoms of dengue may be observed around 4–10 days after the bite of an infected mosquito. Common symptoms are like those of the flu, with patients experiencing: 

• fever, 
• headaches,
• pain behind the eyes, 
• muscle and joint pain, 
• nausea/vomiting, 
• rash and 
• fatigue. 

As the disease progresses, patients can also experience respiratory distress, bleeding from the nose and gums and rapid drop in blood pressure leading to shock. If left unmanaged, this can lead to death. Sound case management of dengue in hospitals has helped to reduce case-fatality rates to less than 1% in most affected countries. 

• Dengue is increasing at a faster rate than any other communicable disease, with a significant increase over 24 years (2000–2024). Annual dengue incidence is estimated to be in the order of 100 million symptomatic cases a year, with another ~300 million asymptomatic infections. The greatest burden is seen in Asia (75%), followed by Latin America and Africa. 2024 recorded the highest levels of dengue with 14 305 764 cases and 10 576 deaths reported from 112 countries to WHO. WHO has established a global dengue surveillance dashboard to track cases from all regions. (https://worldhealthorg.shinyapps.io/dengue_global/) 

There are no specific antiviral treatments against dengue fever. Acetaminophen (Paracetamol) is indicated to bring down the fever. Acetylsalicylic acid (Aspirin) and related non-steroidal anti-inflammatory drugs (such as Ibuprofen) should be avoided. 

Recovery from infection by one dengue virus provides lifelong immunity against that particular virus serotype. However, this immunity confers only partial and transient protection against subsequent infection by the other three serotypes of the virus. Evidence suggests that sequential infection increases the risk of developing severe dengue. The time interval between infections and the particular viral sequence of infections may also be of importance. 

Currently, only one vaccine is available for dengue prevention. WHO recommends the use of Q-denga (TAK-003) in children aged 6–16 years in settings with high intensity of dengue transmission. The vaccination course consists of two injections given 3 months apart

The best way to prevent infection is to avoid being bitten by mosquitoes during the daytime. Mosquitoes that transmit dengue virus often live in and around the home and in the garden. People should: 

• wear clothing that covers the body well (especially the legs and feet);  
• keep mosquitoes out of the house by placing insect screens over doors and windows;  
• apply insect repellents according to the manufacturer’s label instructions;  
• sleep under a net, during the day;  
• take extra precautions to prevent transmission if a family member is infected by avoiding mosquito bites; and 
• clean the surroundings and prevent water stagnation in and around homes.