Zika virus infection

What is Zika virus infection?

Zika virus infection is a mosquito-borne disease caused by Zika virus. Symptoms typically begin 3-14 days after the bite of an infected mosquito. Most Zika virus infection is asymptomatic. The most common symptoms of Zika virus infection are fever and skin rash, usually accompanied by conjunctivitis, muscle or joint pain and general malaise. These symptoms are usually mild and last for a few days.

The current major concern is the association with adverse pregnancy outcome (microcephaly) and neurological and autoimmune complications such as Guillain-Barré syndrome (GBS). The World Health Organization has concluded that Zika virus infection during pregnancy is a cause of congenital brain abnormalities, including microcephaly, and that Zika virus is a trigger of GBS.

Apart from GBS, acute disseminated encephalomyelitis (a disease of the central nervous system) was also found to be one of the neurologic manifestations possibly resulted from Zika virus.

How does it spread?

Zika virus is mainly transmitted to humans through the bite of an infected Aedes mosquito. Aedes aegypti, which is currently not found in Hong Kong, is considered the most important vector for Zika virus transmission to humans. Other Aedes mosquito species such as Aedes albopictus which is commonly found in Hong Kong are also considered as potential vectors.

Zika virus has also been found in human semen and transmission by sexual contact has been confirmed. Sexual transmission of Zika virus between men who have sex with men has also been reported in the literature. Other modes of transmission such as blood transfusion and perinatal transmission are possible.

How can you prevent it?

At present, there is no effective vaccine against Zika virus infection. To prevent Zika virus infection, travellers are reminded to protect themselves from mosquito bites. The personal protection measures against mosquito bites are as follows:

• Wear loose, light-coloured, long-sleeved shirts and trousers;
• Stay in air-conditioned or mosquito-screened rooms;
• Use aerosol insecticide indoor and use bed nets if sleeping areas are not air-conditioned or screened;
• Avoid using fragrant cosmetics or skin care products;
• Use insect repellents containing DEET on exposed skin and clothing;
• Re-apply insect repellents according to instructions;
• If travelling in endemic rural areas, carry a portable bed net and apply permethrin (an insecticide) on it. Permethrin should NOT be applied to skin.

If going to areas with Zika virus transmission (affected areas), travellers, especially people with immune disorders or severe chronic illnesses, should arrange a consultation with doctor at least 6 weeks before the journey, and to have extra preventive measures to avoid mosquito bite.

Travellers who return from affected areas should apply mosquito repellent for at least 21 days after arrival in Hong Kong. If feeling unwell e.g. fever, should seek medical advice as soon as possible, and provide travel details to doctor.

Prevention of sexual transmission*:

1. Travellers should consider not having sex during travel to affected areas, or else condoms should be used.
2. Male and female travellers returning from affected areas should abstain from sex for at least 3 months and at least 2 months respectively upon return, or else condoms should be used.
3. Pregnant woman should not have sex with her partner who had travelled to affected areas, or else condoms should be used throughout the pregnancy.

*This precautionary measure may be revised as more information becomes available. Individuals with further concerns regarding potential sexual transmission of Zika virus should contact their doctor for advice.

Special notes for pregnant women and women preparing for pregnancy:

• Pregnant women should not travel to areas with Zika virus transmission. Women preparing for pregnancy should note Points A and B above. If they or their male sex partners plan to travel to affected areas, they should consult their doctors for advice on the risk. Use of mosquito repellent containing DEET during travel and returning from these areas for a period of at least 21 days are advised for all travellers including pregnant women.
• Pregnant women are advised to:
  • Attend antenatal follow up regularly and tell the attending doctor history of recent travel;
  • observe for symptoms of Zika virus infection and seek medical advice as soon as possible if feeling unwell;
  • abstain from sex with her partner who had travelled to affected areas, or else condom should be used throughout the pregnancy.

How is it treated?

There is no specific medication for Zika virus infection and the mainstay of treatment is symptomatic relief and prevent dehydration. If symptoms worsen, they should seek medical advice immediately.

Zika-virus affected areas

Please refer to website of the Centre for Health Protection for the areas with Zika virus transmission (http://www.chp.gov.hk/en/view_content/43209.html).