Dengue Fever

Dengue fever is an illness you can get from the bite of a mosquito carrying one of four types of dengue virus (DENV). The virus is most commonly found in tropical and subtropical regions, including Central and South America, Africa, parts of Asia and the Pacific Islands.

Dengue isn’t contagious from person to person except when passed from a pregnant person to their child. Symptoms are usually mild with your first infection, but if you get another infection with a different version of DENV, your risk of severe complications goes up.

Who does dengue fever affect?

Dengue is most commonly found in Central and South America, Africa, parts of Asia and the Pacific Islands. A few parts of the U.S. also have dengue. Those living in or traveling to these regions — more than half the people in the world — are most at risk. Children and those who are elderly are at higher risk for serious illness.

How common is dengue fever?

Research estimates that nearly 400 million people get infected with dengue each year, but most (about 80%) have no symptoms.

Can you be immune to dengue fever?

Yes, you can get immunity to a version of dengue virus once you’ve been infected with it. Because there are at least four versions (strains) of the virus (DENV), this is pretty complicated.

Your immune system has tools it can use to recognize infections and get better at fighting them off. As your body fights a virus, it looks through its toolbox to find out which tool (antibody) it has that can destroy that specific threat.

Antibodies are specific to each harmful invader to your body, fitting to them like a key to a lock. Antibodies grab onto their specific target and your immune system destroys it. Once your body knows how to fight that specific virus, you are unlikely to get sick with it again.

After getting one of the four strains of DENV, you shouldn’t be able to get that one again. But the antibodies for that strain don’t fit other versions quite perfectly. So if you get infected by a different version of DENV later on, it can actually use this imperfect fit to trick your immune system (antibody-dependent enhancement).

The different strain can get caught by the antibody from the first strain you had and get pulled into your cells, but — for reasons not fully understood — it’s not destroyed. It’s then inside your cells without your cells knowing it’s harmful. This makes it easier for the virus to infect you and cause more serious illness.