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Zika Virus Infection (Zika Fever)

The Zika virus infection is prevalent in Latin American countries, including on the site of the 2016 Olympics.
Although there have been no reports of patients infected with the Zika virus in Japan to date, some people have been infected with the Zika virus during their stays in epidemic areas, and have developed Zika virus infections after their return home.
Editorial supervisors: Professor Kyoji Moriya/Instructor Shu Okugawa, Department of Infection Control and Prevention

What is the Zika virus infection?

The Zika virus infection develops after being infected with the Zika virus. The chief symptoms include mild fever, skin rash, conjunctivitis, joint pain, muscle pain, a sense of malaise, and headache. No drugs or effective vaccines are currently available for treatment. Therefore, patients suffering from the Zika virus infection should be administered symptomatic therapies. The Zika virus is primarily transmitted to people through bites from infected mosquitoes. Thus, the disease is not transmitted directly from person to person, although transmission of the virus through blood transfusions or sexual intercourse is possible. Although the incubation period is not clearly defined, it generally lasts a few days to about a week. Mild symptoms appear but disappear within two to seven days. Not all of the persons infected with the Zika virus experience symptoms. Some infected persons experience no symptoms, or may not notice mild symptoms.

Pregnant women should be wary of the Zika virus infection

Being infected with the Zika virus during pregnancy can cause serious birth defects, including microcephaly. Pregnant women and women of childbearing potential are advised to avoid areas of Zika outbreaks. Those compelled to go to these areas must consult with their physicians and take effective measures to protect themselves against mosquito bites.

Is the Zika virus spread by the mosquito species living in Japan?

Aedes aegypti and Aedes albopictus have been identified as the two species of mosquitoes that spread the Zika virus. Currently, Aedes aegypti mosquitoes are not normally found in Japan. However, Aedes albopictus mosquitoes live in almost all areas below the Akita Prefecture and the Iwate Prefecture. Therefore, a person may visit an endemic area and be infected there. During this episode, the person (a returnee or foreign traveler) may get a mosquito bite in Japan. This mosquito may bite a different person. Although this is not always the case, there is a possibility that this person will be infected with the Zika virus. Even in this case, the areas infested with mosquitoes are limited, and adult mosquitoes cannot survive the winter. Therefore, the most likely scenario involves transient infections in limited areas.

Actions to be taken in the event of a mosquito bite in an endemic area

The Ministry of Health, Labour and Welfare provides information about the Zika virus infection on its website. People going to endemic areas should check the relevant information thoroughly and take appropriate actions to protect themselves against mosquito bites. For example, they should wear long-sleeved clothes and long pants and use a bug spray. Should you be bitten by a mosquito in an endemic area, it is unnecessary to worry too much about this event, as not all mosquitoes carry the Zika virus. However, those concerned about a possible Zika virus infection should visit the quarantine station at the airport for a consultation when they return home. Those experiencing problems after returning home should go to a nearby health center for a consultation, and those with any symptoms such as fever should go to the hospital to receive examinations and treatment.

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