Prevent Mosquito Bites to Protect from Infection

Kate GAYNOR, Family Medicine Physician

Mosquitoes are a fact of life in Guangzhou. The pesky little creatures even get into my 24th floor apartment. Most of the time their bites are just a nuisance, but mosquitoes can carry a number of different infectious illnesses. Let’s talk about three of them – Zika virus, Japanese encephalitis and dengue.

Zika virus has gotten a lot of press [these years] because it has spread to new geographic areas and been identified as a cause of fetal microcephaly (when a baby has an abnormally small head). So far, all cases of Zika which have been identified in China have been imported from outside the country, meaning the infected people got bitten in another country, not here in China. Infection can also be spread by an infected man to his intimate partner. For now, Zika is only an issue when planning travel and even then, mostly just for pregnant ladies. Most people infected by Zika have a mild illness with fever and do not even go to a doctor. Infection does not cause problems with future pregnancies; it is only dangerous for the baby when the mother acquires the infection during pregnancy. There is no vaccine against Zika virus and no cure.

Japanese encephalitis (JE) is an infection that does occur here in Southern China. It is endemic, meaning it is always around. The chance of infection is much higher in rural areas, but we do see an occasional case in Guangzhou. Encephalitis is inflammation of the brain, which can be very serious, but most people who become infected with the virus never even know. Only one percent of infected people have symptoms. Those who do, however, are very sick. Illness typically begins with fever, headache and vomiting and may progress to tremors, paralysis, seizures or delirium. About one of four people ill with JE will die. Of those who survive, as many as half will suffer ongoing symptoms. There is no cure for Japanese encephalitis. All doctors can do is provide supportive care like anti-seizure medication or assistance with breathing.

There are several vaccines against JE. In China the only source is the community clinic. The JE vaccine called SA 14-14-2 is available here and endorsed by the World Health Organization as being safe and effective. An international JE vaccine is available in Hong Kong.

Dengue is another mosquito-borne infection that we see regularly in Guangzhou. There are cases every year, but 2 years ago there was a large outbreak with about 40,000 confirmed dengue infections in Guangdong. The dengue virus causes fever, joint pains, headache, and rash. It is sometimes referred to as “break bone fever” because of the pain. A small percentage of cases progress to “dengue hemorrhagic fever” which causes bruising, bleeding from the nose or gums, and sometimes internal bleeding. There is no dengue vaccine and no cure. Treatment consists mainly of pain medicine and hydration.

The best thing one can do to avoid any mosquito-borne illness is to keep from getting bitten in the first place. When possible, wear long sleeves or long pants, use a bed net, or apply an insect repellant that contains DEET (the active ingredient in insect repellent products). It is safe to use DEET insect repellent on small children over 2 months of age, but you should apply it by spraying into your own hands and then rubbing it on to the skin rather than just spraying directly onto the child. That makes it easier to avoid getting the repellent into the child’s mouth or eyes or on their fingers where they might put it in their mouth.

You can also decrease the risk of infection by eliminating potential mosquito breeding areas, such as empty standing water from potted plants, buckets or kiddies’ pools. Clean out flower vases and pet water dishes at least once a week.