Chikungunya, Dengue Fever, Yellow Fever And Zika

Chikungunya, Dengue Fever, Yellow Fever and Zika are mosquito-borne diseases transmitted to humans by day-biting Aedes aegypti and Aedes albopictus mosquitoes.

Dengue Fever

There are two types of illnesses that can result from infection with dengue virus: dengue and severe dengue. Dengue causes high fever, severe headaches and joint pain. This illness can progress to a hemorrhagic fever during which patients experience more bleeding and persistent vomiting. If not treated, it can progress to shock and death. No locally acquired cases of dengue have been detected in California to date. However, many travelers have contracted the disease in other countries where dengue is endemic, then returned to the U.S. ill with the virus. If those returning to the U.S. with the disease live in areas where the mosquito vectors are found, these mosquitoes can pick it up by feeding on infected persons then spread it to others through their blood-feeding activities.


Zika is a mosquito-borne virus consisting of a mild fever, rash, joint pain and red eyes. Zika virus can also be transmitted, person to person, from sexual contact with an infected partner. Most infected people have no symptoms. If symptoms do occur, they will begin 3-7 days after a person is infected. Outbreaks of Zika have occurred in areas of Africa, Southeast Asia, the Pacific Islands, Caribbean Islands, South and Central America and Mexico. The list of affected countries continues to expand. Recently, local transmission has been observed in Florida and Texas. The Centers for Disease Control and Prevention has issued a travel alert regarding Zika. The alert is due to reports of Zika infected mothers giving birth to babies with microcephaly. Researchers are still discovering new symptoms and effects caused by Zika, particularly in developing fetuses. The mosquito capable of transmitting Zika is not found in Sutter or Yuba Counties at this time. Search CDC’s interactive world map to see travel recommendations for Zika at that location.
Microcephaly is a birth defect resulting in abnormally small heads (see photo) and underdeveloped brains. Pregnant women and women trying to become pregnant should not travel to countries where mosquito-borne Zika virus transmission is ongoing. Thus far in California, Zika virus infections have been documented only in people who were infected while traveling outside the United States or through sexual contact with an infected traveler. To date there has been no local mosquito-borne transmission of Zika virus in California. This CDC Factsheet is helpful in understanding more about Zika.

For more information, please download our Zika brochure.


Chikungunya is an infectious disease that is characterized by acute onset of fever and severe joint pain. The most common symptoms are fevers and painful joints in the hands and feet. Other symptoms may include headache, muscle pain, joint swelling or rash. Symptoms usually begin 3-7 days after being bitten by an infected mosquito. This is another disease that is spreading around the world and could come here by means of infected travelers returning to areas of California that have the mosquitoes that are capable of spreading it to other people.

Yellow Fever

Yellow fever can cause fever, jaundice, liver failure and kidney failure. The majority of people infected with yellow fever are hospitalized. Yellow fever vaccines ARE available and are highly recommended for people traveling to destinations where yellow fever is present- like Africa and South America. Fortunately, yellow fever vaccines are very effective. Hopefully, researchers will be able to develop vaccines for dengue, zika and chikungunya.

Please review the following articles below or visit the Centers for Disease Control and Prevention website for more information regarding these diseases. All articles are available in English and Spanish formats.

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