Across the globe, of all the animals that are dangerous to humans, which one is the most dangerous? The teeny, tiny mosquito. More than 1 million people worldwide die from mosquito-borne diseases annually according to the American Mosquito Control Association. Grabbing headlines lately is the Zika virus, a suspected cause of microcephaly, a serious birth defect. But there several others to know about. Here are six of them.

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The Chikungunya virus has been found in Africa, Asia, Europe, the Indian and Pacific Oceans and the Caribbean according to the Centers for Disease Control and Prevention (CDC). The first U.S.-acquired case was reported in Florida in 2014. No locally transmitted cases were reported in 2015.

Chikungunya was named for a Mozambique dialect word meaning ''that which bends up." That's due to the excruciating joint pain that's a major symptom of Chikungunya. Other symptoms include fever, headache and rash.

No vaccine is available. Pain medicine is the main treatment, along with fluids and rest.


Not-so-fondly known as breakbone fever, dengue causes agonizing bone and muscle pain along with severe pain behind the eyes. It can also cause persistent vomiting, a high fever that lasts from two to seven days, severe headache, joint pain and a rash. The nose or gums may bleed easily.

Dengue is rarely found in the continental United States, but it does occur in Puerto Rico, Latin America, Southeast Asia and the Pacific Islands, including many popular tourist destinations. The Big Island of Hawaii saw a large dengue outbreak in 2015. CDC estimates there are more than 100 million cases of dengue worldwide each year.

No specific treatment exists. Non-aspirin pain relievers can help with the pain. Rest and fluids are also advised. If vomiting or severe abdominal pain occur, the CDC says emergency care is advised. Soberingly, the CDC notes: “When infected, early recognition and prompt supportive treatment can substantially lower the risk of medical complications and death.”

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Several diseases involving encephalitis, or inflammation of the brain, can be transmitted by various kinds of mosquitoes. Among them are Eastern Equine Encephalitis (most cases occur in the Atlantic and Gulf Coast states), Western Equine Encephalitis (most commonly reported from states and Canadian provinces west of the Mississippi River), St. Louis Encephalitis (found mainly in the Mississippi Valley and along the Gulf Coast) and La Crosse Encephalitis (found mainly in the upper Midwestern and mid-Atlantic and southeastern states).

Symptoms vary and may be mild, including fever and headache. But some people become seriously ill.

No human vaccine is available. Treatment is mainly supportive, including fluids and hospitalization if needed.


Malaria is still a killer. Hundreds of thousands of people die from it each year, mostly children in Africa. It’s caused by a parasite that infects a certain type of mosquito.

About 1,500 cases of malaria are diagnosed in the United States each year, according to the CDC. Most U.S. cases are brought in by travelers returning from areas where malaria is common, such as sub-Saharan Africa and South Asia. Symptoms are flu-like, with chills, fever and shaking. Nausea and vomiting may occur, as well as jaundice. Prompt medical attention is needed.

Treatment is aimed at the parasite and includes a variety of drugs, such as mefloquine (Lariam) and chloroquine. A vaccine is in development. Meanwhile, travelers can take anti-malarial drugs before departing.

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West Nile virus

In 2015, the U.S. reported 119 deaths from West Nile, which appears in 48 states and the District of Columbia. It’s most prevalent in the summer.

If you develop West Nile you might not even know it: Most people have no symptoms. One in five people develop a fever and other symptoms, including headache, joint or body pain, diarrhea, vomiting and rash. Less than 1 percent of people develop neurological problems. According to the CDC, symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis.

No treatment or vaccine exists. Pain relievers can help, but people with severe cases may need to be hospitalized.

Yellow fever

Yellow fever is found in subtropical areas of South America and Africa. According to the CDC, it’s a “very rare” cause of illness in U.S. travelers.

Most infected people have no illness or a mild one. In others, symptoms may include fever, chills, severe headache, back pain and nausea. About 15 percent of people may go on to develop more severe illness, with jaundice, bleeding and organ failure.

No treatment other than rest, fluids and pain relievers other than nonsteroidal anti-inflammatory drugs (which can increase bleeding) is available. Hospitalization may be advised for observation and supportive care. A vaccine is available and may be required for entry to some countries.

Avoiding mosquito bites

Your best defense against these diseases is to avoid being bitten. If you’re out where and when the mosquitos are, protect yourself with a long-sleeve shirt and long pants. The CDC advises using an insect repellent that is Environmental Protection Agency (EPA)-registered, with one of these active ingredients:

  • DEET
  • Picaridin (also called KBR 3023, Bayrepel and icaridin)
  • Oil of lemon eucalyptus or para-menthane-diol
  • IR3535

Treating items such as boots, tents, socks and pants with permethrin can also help. At home, repair screens and get rid of any standing water in buckets or planters.

Related: Natural Mosquito Repellents: Which Ones Work?

Kathleen Doheny is a Los Angeles journalist specializing in health, behavior and fitness topics.