Fact Sheets


Mosquitoes are carriers of diseases that can affect humans around the world. While the diseases are generally
less common n the US, global climate change and rising temperatures are increasing the range of some mosquito
species, which may lead to an increased incidence of mosquito-borne diseases in widening regions of the world.


MALARIA. More than 241 million cases of malaria occurred globally in 2020 with about 2,000 cases reported annually in the U.S. Most US cases occur in people returning from international travel from countries in sub-Saharan Africa and South Asia, according to CDC. Through August 2023, only 9 cases of locally acquired malaria were reported for the year in the US, meaning that the overall US risk is extremely low. But malaria is a serious disease caused by a parasite that infects Anopheles mosquitoes, which can be transmitted to humans via a bite. This mosquito can also transmit malaria from person to person even if the mosquito itself is not infected. Symptoms of malaria can range from fever and flu-like illnesses to serious symptoms of kidney failure, seizures, and coma. Properly administered prescription treatments can effectively treat and cure malaria, so seeking prompt medical attention is important.

DENGUE (breakbone fever). Dengue is a viral infection that is spread primarily by bites from female Aedes aegypti mosquitoes with about 5 million cases reported globally each year. When the mosquito bites a person with Dengue, the virus replicates in the mosquito reaching an infectious level within 12 days (when the ambient temperature is 77-82°F). Transmission to others then occurs through subsequent bites. According to the World Health Organization (WHO), about 5 million cases occurred globally in 2019; but since most cases are asymptomatic or mild, it’s likely that the numbers are significantly underreported. The Americas, South-East Asia, and Western Pacific regions are the most seriously affected, with Asia representing around 70% of the global disease incidence. Dengue outbreaks occasionally occur in the continental US with about half related to travel. Per the CDC, as of August 16, 2023, more than 600 cases were reported from an area including the 50 states, District of Columbia, 5 US territories and 3 freely associated states. When they occur, Dengue symptoms include very high fever (~104°F) and severe headache 4-10 days after a bite, that can persist for up to 7 days. After the fever goes away, severe abdominal pain, bleeding and GI impacts can occur. Treatment relies on treating the symptoms with nonspecific drugs aimed at pain reduction.

CHIKUNGUNYA. Chikungunya is a mosquito-borne viral disease whose symptoms resemble Dengue and is also transmitted by an infected Aedes species of mosquito, so it can be misdiagnosed. While most Chikungunya cases in the US are related to travel in affected areas in Africa and Asis, rare locally acquired cases have been reported.

ZIKA. Zika is a mosquito-borne viral disease spread to people primarily through the bite of an infected Aedes species of mosquito. Infections are typically asymptomatic or present only very mild symptoms including fever, rash, headaches, and other pains. However, infection during pregnancy can cause a birth defect of the brain in the developing fetus. In 2015-2016, cases of Zika virus spread from Brazil to the Southern US, causing tens of thousands of cases. But cases have decreased dramatically in recent years, with 2017 seeing the last case of locally acquired Zika in the US, though it persists in several countries including Africa and the Caribbean among others, per the WHO. Transmission can also occur through objects that may be contaminated with bodily fluids.


Preventing mosquito-borne diseases relies on avoiding areas where mosquitoes are found, such as near standing
water. Using mosquito repellants and/or mosquito nets and ensuring that window and door screens are intact can
help deter mosquitoes. It’s also important to be aware of when infectious mosquitoes are active, so precautions can
be effectively implemented: Anopheles mosquitoes that carry malaria are active at night; Aedes species that carry
Dengue, Chikungunya and Zika, during the day.

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