Avoiding Mosquito-Borne Diseases
Malaria is a common disease caused by a microscopic parasite that is passed along from one infected person to another by mosquitoes. Malaria occurs in more than 100 countries worldwide, infecting 300 million to 500 million people, and causing about 1 million deaths, each year.
Nearly all cases of malaria treated by doctors each year in the United States are acquired overseas, according to the U.S. government's Centers for Disease Control and Prevention (CDC).
The Malaria Zone:
Malaria can resemble the flu, with fever (most common), chills, sweating, back pain, vomiting and diarrhea. Anyone who comes down with these symptoms after visiting a country where malaria is found should seek prompt medical attention. Certain forms of malaria can cause coma, kidney failure and death. Symptoms usually develop within a week to a month of the mosquito bite, but the onset of symptoms may be delayed for up to a year.
Malaria parasites are carried by Anopheles mosquitoes, which usually bite during nighttime hours, from dusk to dawn. Insect repellants should be used to help prevent malaria and other insect-borne diseases, including yellow fever, dengue fever and Japanese encephalitis.
A malaria vaccine is under development but is not currently available.
The following prescription drugs can prevent malaria infection and always should be taken by travelers visiting areas with high rates of malaria. The type of medication recommended depends on the rate of resistance to the drug chloroquine in the countries you are visiting.
Chloroquine is the treatment of choice for malaria, but it is recommended only for travel to countries where the malaria parasites are not yet resistant to it. These include Mexico, Central America, Haiti and the Dominican Republic. You should take a dose one week before leaving, once a week during the trip and once a week for the four weeks after returning.
Mefloquine is now being used widely because many malaria-causing parasites have become resistant to chloroquine. Take a single dose one week before travel, once a week throughout the trip and once a week for four weeks afterward.
Doxycycline is an antibiotic also effective in suppressing malaria parasites. It also is used to treat such tick-borne illnesses as Lyme disease. One disadvantage is that it makes some people hypersensitive to the sun. A hat and sunscreen should be used when taking this drug. It is taken daily, beginning two days before travel, each day during the trip, and for four weeks afterward.
Malarone is an alternative to mefloquine and doxycycline for chloroquine-resistant malaria. It is a combination of the drugs atovaquone and proguanil. It is taken daily, beginning one to two days before travel, each day during the trip and for one week afterward.
Warding off mosquitoes:
Note: Neither ultrasound devices nor vitamin B tablets will ward off mosquitoes or prevent malaria.
Dengue fever is caused by a virus that usually is transmitted by Aedes mosquitoes. These insects attack in a pattern opposite to that of malaria-carrying mosquitoes. That is, they bite by day, usually in the early morning or late afternoon, and are most common in the cities. Risk to travelers is usually small, unless there is an epidemic in the area.
The Dengue Zone:
Central and South America, Caribbean, Africa, tropical Asia and Pacific islands.
The spectrum of symptoms varies from a mild, flulike illness to a life-threatening syndrome with severe bleeding. Common symptoms include high fever, severe headache, joint and muscle pain, nausea and vomiting, loss of appetite and altered taste sensation. A rash on the torso may appear three or four days after onset of the fever and sometimes spreads from there to the arms, legs and face. Symptoms taper off after a few days, though some patients will experience fatigue that may last for weeks.
Note: Neither ultrasound devices nor vitamin B tablets will ward off mosquitoes.
There is no specific treatment other than supportive care for dengue. The disease usually runs its course of five to seven days without incident. However, some patients will develop a life-threatening illness with severe bleeding and require hospitalization. All travelers who experience fever and other symptoms of dengue should see a doctor, either locally or in the United States.
Yellow fever is caused by a virus carried by mosquitoes in jungle areas in parts of Africa and South America. Yellow fever vaccine is recommended for persons aged 9 months and older who are traveling to these areas. While travelers have a very low risk of getting yellow fever, some countries require a yellow-fever vaccination for all travelers, and other countries require a certificate of yellow-fever vaccination for people arriving from countries where the disease is found. For more information, read the CDC's information on yellow fever vaccination requirements.
A vaccine is available by injection. It's needed at least 10 days before traveling. A single dose lasts for 10 years.
Despite its name, very few cases of this disease are seen in Japan. However, large outbreaks occasionally occur in other parts of Asia. The chances of a traveler coming down with an infection of the brain, called encephalitis, from this virus are rare because it is found principally in rural areas. The incidence is low because only a small number of mosquitoes in an area are actually carrying the virus. Of those bitten by an infected mosquito, fewer than one in 50 actually will become seriously ill. However, in those people who are stricken with encephalitis as a result of the infection, about 25% die.
Where and when
Outbreaks can occur in rural areas of:
Flulike illness, with headache and fever, and sometimes stomach upset and diarrhea. Confusion and behavior disturbances also can occur. Can progress to encephalitis, a severe brain infection, resulting in permanent damage or death.
No specific treatment is available, other than symptom control.
Vaccine is available for people who are traveling to areas with a high incidence or an outbreak of Japanese encephalitis and will be frequently outdoors in rural areas.
Note: Neither ultrasound devices nor vitamin B tablets will prevent mosquito bites.