Dengue fever is an acute mosquito-borne viral infection transmitted through the bite of infected female mosquitoes (Aedes aegypti and Aedes albopictus) that feed both indoors and outdoors during the daytime (from dawn to dusk). These mosquitoes thrive in areas with standing water, including puddles, water tanks, containers and old tires. 

Once infected, humans become the main carriers and multipliers of the virus. The virus circulates in the blood of an infected person for 2-7 days. Patients who are already infected with the Dengue virus can transmit the infection via Aedes mosquitoes after the first symptoms appear.

In humans recovery from infection by one Dengue virus provides lifelong immunity against that particular virus serotype. However, if you are infected subsequently with a different serotype, immunity wanes over time which increases the risk of developing Dengue Hemorrhagic Fever.

How serious it is?

Most people recover within a week or so. In some cases, symptoms worsen and can become life-threatening. Blood vessels often become damaged and leaky. And the number of clot-forming cells (platelets) in your bloodstream drops. This can cause a severe form of dengue fever, called dengue hemorrhagic fever, severe dengue or dengue shock syndrome.

Are you at risk of Dengue Fever?

Dengue occurs year-round in Vietnam, with peak transmission in the warmer rainy season (April through October in the north and June through December in the south). Elevated risk occurs throughout the Red River Delta and Mekong Delta, and the coastal district and provincial capitals of central Vietnam. All traveller or expats going to areas when Dengue is endemic during the rainy season are at high risk.


A person infected by the Dengue virus develops severe flu-like symptoms. 
Individuals should suspect dengue when a high fever is accompanied by two of the following symptoms:
•    Severe headache 
•    Pain behind the eyes 
•    Nausea, Vomiting 
•    Swollen glands 
•    Muscle and joint pains 
•    Rash 

Symptoms usually last for 2-7 days, after an incubation period of 4-10 days after the bite from an infected mosquito. The warning signs to look out for occur 3-7 days after the first symptoms in conjunction with a decrease in temperature (below 38°C) include:

•    Severe abdominal pain 
•    Persistent vomiting 
•    Rapid breathing 
•    Bleeding gums 
•    Blood in vomit 
•    Fatigue, restlessness 

The next 24-48 hours of the critical stage can be lethal; proper medical care is needed to avoid complications such as plasma leaking, fluid accumulation, respiratory distress, severe bleeding, or organ impairment. 


If you are in areas where Dengue is endemic, you should take meticulous measures to prevent mosquito bites during the daytime:

•    Use a repellent containing 20%-30% DEET (diethyltoluamide) or 20% Picaridin on exposed skin. Re-apply according to manufacturer's directions. Here are some mosquito repellent could be found easily in Vietnam: Aerogard (picadirin), Remos (mentholatum), Moustidose spray (30% DEET)
•    Wear neutral-coloured (beige, light grey) clothing. If possible, wear long-sleeved, breathable garments.
•    If available, pre-soak or spray outer layer clothing and gear with permethrin. 
•    Get rid of water containers around dwellings and ensure that door and window screens work properly. 

Diagnosing Dengue Fever

If you become sick after traveling to a tropical area, let your doctor know. They can diagnose dengue infection with a blood test to check for the virus or antibodies to it.


There is no specific treatment for dengue fever.  Patients should seek medical advice, rest and drink plenty of fluids. Paracetamol can be taken to bring down fever and reduce joint pains. However, aspirin or ibuprofen should not be taken since they can increase the risk of bleeding.

If you start to feel worse in the first 24 hours after your fever goes down, you should get to a hospital immediately to be checked for complications.


There is a vaccine for endemic population being tested right now. However, a vaccine for travelers or expart in Viet Nam is still unavailable. 

(Edited and Reviewed by Dr Nguyen Hoang Thi - General Practitioner)