It's at the top of this page.

About mosquito-borne infectious diseases

Dengue fever, Zika virus infection, etc.

Final update date April 16, 2019

Mosquito-borne infections are infections when mosquitoes carrying pathogens such as viruses and protozoa suck blood on humans.
West Nile fever, yellow fever, Zika virus infection (Zika fever), chikungunya fever, dengue fever, Japanese Encephalitis fever), Chikungunya fever, dengue fever, etc.

Overseas, many mosquito-borne infectious diseases have been reported.
When traveling abroad, grasp the local epidemic situation and take preventive measures before traveling.
In addition, many of these infectious diseases have been found to be able to transmit mosquitoes (such as Aedes albopictus) that live widely in Japan.
Care must be taken after returning to Japan to prevent the spread of infection from overseas infected people returning home.

To prevent infection, see to prevent infection.

Poster Don't Increase Mosquitoes


  • Cause: Zika virus (Flavi virus)
  • Transmission route: It is transmitted by being bitten by a mosquito carrying the Zika virus (such as Aedes aegypti and Aedes albopictus). In addition, it may be infected by blood donation or sexual intercourse.
  • Occurrence area: It occurs in Asia, Latin America and Caribbean countries, Africa, Oceania and the Pacific Islands, and North America.
  • Symptoms: After an incubation period of 2 to 12 days (often 2 to 7 days), mild fever, headache, joint pain, muscle pain, rash, conjunctivitis, etc. appear. Infection in pregnant women has also been shown to cause fetal microcephaly and neurological symptoms (Giran-Barre syndrome).
  • Treatment: There is no special treatment for symptomatic treatment.
  • Prevention: There is no vaccine. It is the only way to prevent mosquito bites.

In particular, be aware of the following:

  1. For those traveling to endemic areas

Take sufficient measures to prevent mosquito bites! Please refer to "To prevent infection" for the countermeasures.

  1. For pregnant women and their partners

Pregnant Zika virus infection can cause fetal microcephaly.

If you are pregnant or pregnant, refrain from traveling to endemic areas as much as possible.

If you must travel, it is necessary to take strict mosquito control measures locally.


In addition, the following are recommended for the prevention of sexual transmission.

  • Both men and women are staying in endemic areas and returning from endemic areas for at least six months (if their partner is pregnant, during pregnancy), regardless of symptoms, use condoms or refrain from sexual activity. thing.
  • For women who have traveled to endemic areas and wish to have a child, refrain from pregnancy for at least six months, regardless of symptoms.

To medical institutions

For more information about Zika virus infection

  • Cause: Dengue virus (Fravi virus)
  • Transmission route: It is transmitted by being bitten by a mosquito carrying the dengue virus (such as Aedes aegypti and Aedes albopictus).
  • Occurrence area: It occurs in tropical and subtropical regions such as Asia, Latin America and Africa. Every year, it is reported that there are 50 million to 100 million patients worldwide.
  • Symptoms: After an incubation period of 2 to 15 days (often 3 to 7 days), sudden fever, headache, joint pain, muscle pain, rash, etc. appear. Some may have severe dengue hemorrhagic fever.
  • Prevention and Treatment: There is no vaccine. In addition, there is no special treatment and symptomatic treatment is performed.

In recent years, reports of people who become infected overseas and develop symptoms after returning to Japan have increased, and in 2014, domestic infection was confirmed for the first time in about 70 years.
(For the response of Yokohama City at that time, please see the page on "Response to domestic cases of dengue fever.")
About 10 to 20 people are reported every year in Yokohama, so care must be taken. Please refer to "To prevent infection" for the countermeasures.

To medical institutions

Dengue fever details

  • Cause: Chikungunnia virus (Toga virus alpha virus)
  • Transmission route: It is transmitted by being bitten by a mosquito carrying the chikungunya virus (such as Aedes aegypti and Aedes albopictus).
  • Occurrence area: It occurs in Africa, South Asia and Southeast Asia. The epidemic was reported in Italy in 2007.
  • Symptoms: After an incubation period of 3 to 12 days (usually 3 to 7 days), sudden fever, joint pain, headache, muscle pain, rash, etc. appear.
  • Prevention and Treatment: There is no vaccine. In addition, there is no special treatment and symptomatic treatment is performed.

For more information about Chikungunya fever

  • Cause: West Nile Virus (Flavi virus)
  • Transmission route: In nature, infections are repeated between birds (mainly crows) and mosquitoes. It is transmitted by being bitten by a mosquito carrying the West Nile virus (eg, locusts such as aca, albopictus such as Aedes albopictus).
  • Occurrence area: It occurred in a wide area of Africa, Europe, the Middle East, Central Asia, and West Asia, but epidemics have also occurred in western hemispheres such as Europe and the United States, which had not been reported until recently.
  • Symptoms: After an incubation period of 2 to 14 days, sudden fever, headache, back pain, muscle pain, rash, etc. appear. Severe cases can cause meningitis and encephalitis.
  • Prevention and Treatment: There is no vaccine. In addition, there is no special treatment and symptomatic treatment is performed.

For more information about West Nile fever

  • Cause: malaria

Plasmodium vivas (three-day thermal malaria protozoa), plasmodium fallicamum (tropical thermal malaria protozoa), plasmomidimium-infected malariae (four-day thermal malaria), and Plasmodimium-infected malariae.

  • Transmission route: It is transmitted by being bitten by a mosquito (Hamadaraka) that holds malaria protozoa.
  • Occurrence area: It occurs in tropical and subtropical regions such as Africa, Asia, the South Pacific countries, and Latin America. According to estimates by the World Health Organization (WHO), there are more than 200 million affected people and 2 million deaths annually. In Yokohama, there are several reports of people infected overseas every year.
  • Symptoms: After an incubation period of 10 to 30 days, fever, facial crimson, headache, muscle pain, respiratory symptoms, gastroenteritis symptoms, etc. appear. Fever repeats fever and non-heat. (The incubation period, symptoms, and fever interval vary depending on the type of malaria protozoa.) If not treated promptly, it may become severe and die.
  • Prevention and Treatment: Preventive antimaria drugs are effective. Also, if you are diagnosed with malaria, you will be treated with antimalaria.

For more information about Malaria

  • Cause: Yellow fever virus (Flavi virus)
  • Transmission route: It is transmitted by being bitten by a mosquito carrying the yellow fever virus (mainly Aegypti).

There are three transmission rings:
(1)Tropical rain forest (forest) type cycle: Sacred lilies other than humans-mosquito-celebrities other than humans (incidentally transmitted to humans)
(2)Urban cycle ...
(3)Mid-term (Savanna) cycle: Human-mosquito-Minerals other than humans
Urban cycles can cause large-scale outbreaks.

  • Occurrence area: It is popular in the tropical region of Africa and Latin America. According to estimates by the World Health Organization (WHO), there are 80,000 to 170,000 affected people and 60,000 deaths annually.
  • Symptoms: After an incubation period of 3 to 6 days, fever, headache, muscle pain, back pain, vomiting, etc. appear. Many people have no symptoms when infected or only mild symptoms, but about 15% of the affected people become more severe. In that case, refurbishment of high fever and jaundice and bleeding tendency progress, following a few hours to one day of remission (not completely cured but temporarily reduced or lost symptoms). It is said that 50% will die.
  • Prevention and Treatment: Vaccinations is good. Treatment is centered on symptomatic treatment. Depending on the country, you may be required to show a yellow fever vaccination certificate when entering the country. Yellow fever Vaccinations can be inoculated only by a specific inoculation body.

For more information about yellow fever

For those traveling abroad-Be careful not to get stuck by mosquitoes! ~~

Points of Use of Insect Repellents (Reference: Guidelines for Treatment of Mosquito-Infections)

  • Choose one that contains the effective ingredients "DET" and "Ikaline" to prevent mosquitoes.
    (In Japan, deep is sold at a maximum of 30% and squid is sold at a maximum of 15%.)
  • Follow the usage and procedures and precautions according to your age, and use them properly.
  • Water and sweat reduce the sustainability of the effect, so try to repaint it frequently.
    If you use sunscreen, apply an insect repellent on top of it.
  • Don't forget small exposed parts such as neck, ears, back of hands, and ankles.
  • Use mosquito coils and mosquito nets indoors to take measures to prevent mosquito bites.
    (Aedes aegypti are working indoors.)
  • If you have symptoms such as fever after returning home or returning home, quarantine stations or quarantine stationsThe nearest Health and Welfare CenterPlease consult with us.
  • If you have symptoms such as fever, do not take commercially available antipyretic analgesics.
  • After returning to Japan, take measures to prevent mosquito bites for about two weeks without any symptoms.
  • To prevent the spread of blood transfusion, refrain from donating blood within 4 weeks from the date of return from overseas.
  • Infectious disease control when traveling abroad is summarized."For those traveling abroad" pageSee also.

Let's reduce mosquitoes around us.

Please see the flyer "Beware of Mosquitoes" (PDF: 623KB) (Updated February 2018) for measures against Aedes albopictus.

If you have a history of traveling abroad ... Please consider introducing Yokohama Municipal Citizen's Hospital's introduction, including the differential from other viral diseases.

If you do not have a history of traveling abroad ... If dengue fever or Zika virus infection is strongly suspected based on the progress or consultation results, we will consider a test at the Yokohama City Institute of Health, so please consult below.

[Weekdays from 8:30 to 17:15] Contact information for Health and Welfare Center Health and Welfare Division Health Promotion Section.

[Outside hours above] Contact information for each ward Health and Welfare Center outside of the above hours

2017

June 1, 2017 "We will call for mosquito countermeasures by bus and subway-do not increase mosquitoes this summer! Don't get bitten by mosquitoes! ~ "Press release document (PDF: 405KB)

2016

May 18, 2016 Press release document (PDF: 733KB) "We will strengthen prevention awareness of mosquito-borne infectious diseases"

2015

June 2, 2015 "We will start mosquito monitoring surveys at 25 locations in the city!" Press release document (PDF: 348KB)

Adobe Acrobat Reader DC (formerly Adobe Reader) is required to open PDF files.
If you do not have it, you can download it free of charge from Adobe.
Get Adobe Acrobat Reader DCTo download Adobe Acrobat Reader DC

Inquiries to this page

Health and Social Welfare Bureau Health and Safety Department Health and Safety Division

Telephone: 045-671-2463

Telephone: 045-671-2463

Fax: 045-664-7296

Email address: [email protected]

Return to the previous page

Page ID: 197-460-950

return to the top