Zika is a mosquito-borne disease caused by Zika virus that is mainly transmitted to humans through the bite of an infected Aedes mosquito which is the same type of mosquito that spreads dengue, chikungunya and yellow fever.
Most Zika is asymptomatic. For patients with symptoms, they commonly present with skin rash, fever, conjunctivitis, muscle and joint pain, malaise and headache. The incubation period of Zika virus infection ranges from 3 – 14 days. These symptoms are usually mild and last for 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 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 found to be one of the neurologic manifestations possibly resulted from Zika.
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 been documented in the literature. Other modes of transmission such as blood transfusion and perinatal transmission are possible.
Once a person has been infected, he or she will be likely to be protected from future infections.
Health authorities are currently investigating a link between Zika virus in pregnant women and microcephaly in their babies. According to the World Health Organization, based on research to date, there is scientific consensus that Zika virus is a cause of microcephaly.
Microcephaly is a rare condition where a baby has an abnormally small head. This is due to abnormal brain development of the baby in the womb or the brain has stopped growing after birth. Babies and children with microcephaly often have challenges with their brain development as they grow older.
Microcephaly can be caused by a variety of environmental and genetic factors such as Downs syndrome; exposure to drugs, alcohol or other toxins in the womb; and rubella infection during pregnancy.
The best protection from Zika virus is preventing mosquito bites and mosquito proliferation. Preventing mosquito bites will protect people from Zika virus, as well as other diseases that are transmitted by mosquitoes such as dengue, chikungunya and yellow fever. The public is also advised to take precautions to prevent sexual transmission of Zika virus.
General measures on preventing mosquito-borne diseases:
1. Wear loose, light-coloured, long-sleeved tops and trousers, and use DEET-containing insect repellent on exposed parts of the body and clothing.
2. Take additional preventive measures when engaging in outdoor activities:
3. Special notes when travelling abroad:
Prevention of sexual transmission*
*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.
Pregnant women should not travel to areas of active 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 areas of active transmission, 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.
Help prevent mosquito proliferation
1. Prevent accumulation of stagnant water
2. Control vectors and reservoir of the diseases
For more information about control and prevention of mosquito breeding, please visit the website of Food and Environmental Hygiene Department (FEHD) at http://www.fehd.gov.hk/english/pestcontrol/handbook_prev_mos_breeding.html
Pregnant women and children of 6 months or older can use DEET-containing insect repellent. For children who travel to countries or areas where mosquito-borne diseases are endemic or epidemic and where exposure is likely, children aged 2 months or above can use DEET-containing insect repellents with a concentration of DEET up to 30%. For details about the use of insect repellents and the key points to be observed, please refer to ‘Tips for using insect repellents'. More information can also be accessed at the World Health Organization website.
There is no specific medication for Zika and the mainstay of treatment is symptomatic relief and prevention of dehydration. If symptoms worsen, they should seek medical care and advice.
Medical advice should be sought. With compatible epidemiological and clinical history, clinicians could liaise with the CHP's Public Health Laboratory Services Branch for consideration of Zika virus testing. Interpretation of test result needs to be made with liaison between the attending clinician and the microbiologist, based on epidemiological and clinical history, and the relative timing of exposure, symptom onset and presentation to medical care.