December 2, 2015
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Travel Medicine (cont.)

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Meningitis and encephalitis

There are several causes of meningitis, an infection of the lining and fluid around the brain and spinal cord. Encephalitis means that the brain tissue itself is also infected. There are serious types of meningitis and encephalitis that are associated with travel and can be prevented.

Meningococcal meningitis is one of the most serious types associated with travel to certain areas. The cause is a bacterium called Neisseria meningitidis. The disease can be quite severe or even fatal. The infection is spread from person to person by close contact through coughing or sneezing or other respiratory means.

Meningococcal meningitis occurs at low rates throughout the world, including the United States. However, some countries have high rates of disease and pose a special risk to travelers. This includes many countries in the "meningitis belt" of sub-Saharan Africa. Saudi Arabia has experienced outbreaks when pilgrims travel to religious sites.

There are two effective vaccines to prevent meningitis. The choice of vaccine depends on the age of the patient. The vaccines are synthetic (meaning that they do not contain live infectious agents). They should not be given to people who have previously had a neurological illness called Guillain-Barré syndrome. Meningitis immunizations are now routinely recommended for adolescents and college freshmen in the United States. It is also recommended for travelers who are going to areas that have high rates of infection. Vaccination is required for pilgrims to religious sites in Saudi Arabia, and proof of vaccination (preferably an International Certificate of Vaccination) will be required at the border. The vaccination is effective for three to five years (depending on which of the two vaccines is given), after which revaccination may be recommended for travelers who travel to areas with high rates of infection.

There are several kinds of viral encephalitis that occur in various areas of the world, such as Japanese encephalitis virus, which are spread by mosquito bites. They are fortunately rare, and most viral encephalitis is prevented by avoiding mosquito bites (see the section on insect precautions). Japanese encephalitis virus is preventable by vaccine, and a doctor or travel clinic can advise if you will need it.

Meningitis and encephalitis caused by parasites (amoebae) is also a concern for travelers. Harmless amoebae are common in freshwater and plumbing all over the world. Naegleria fowleri prefers hot springs, lakes, rivers, or any warm freshwater that is untreated for human use; it may grow in pipes and hot water tanks of homes and buildings as chlorine dissipates. If affected water with enough Naegleria is inhaled, it may cause severe meningoencephalitis; death occurs in 97%-99% of cases. This type of meningitis is hard to diagnose, children are often affected, and effective treatment is still being studied. Prevention is very easy. If bathing in hot springs or bodies of fresh water with unknown chlorination during hot seasons, keep the head above water, hold the nose shut, or use nose clips. Avoid getting bath or hose water up the nose. If you rinse your sinuses, or practice religious nasal cleansing, tap water is safe if boiled for at least one minute and left to cool. Other options include using chemical disinfectants, filters with an absolute pore size 1 micron or less, and distilled or sterile water. Drinking affected water cannot transmit Naegleria, and it cannot live in saltwater.

Yellow fever

Yellow fever virus is a rare cause of illness in U.S. travelers, but it can be serious, and some countries require proof of vaccination before border entry. It is caused by a virus that attacks the liver. Symptoms start within three to five days of infection. In many people, the disease is mild and goes away. About 15% of people will develop severe disease with liver failure, and up to half will die. Yellow fever is spread by the bite of a mosquito.

Yellow fever occurs in areas of sub-Saharan Africa, Central America, and South America. Not all countries in these areas have yellow fever. Even within a country, some areas may have yellow fever while others do not.

There is a very effective vaccine available to prevent yellow fever. It contains a live virus that has been modified ("attenuated") to make it safer. Vaccine side effects are usually mild. Rarely (a few cases per million doses), the vaccine virus can spread and cause severe disease. Infants under 6 months old, and people with weak immune systems (for example, people with certain chronic diseases, and some people with HIV infection or cancer) should not receive the live vaccine. These people should consult with a doctor before traveling to an area where yellow fever occurs. For people 60 or over and pregnant or breastfeeding women, a doctor should carefully review the risks and benefits of the vaccine.

Vaccination is generally recommended for travelers who will be exposed to yellow fever with the above exceptions. The vaccine may be required for entry into some countries. Check the CDC web site to see if vaccination is required for your trip. If you get vaccinated, you should receive an International Certificate of Vaccination, signed and validated with the center's stamp where the vaccine was given. If you cannot be vaccinated, a medical waiver can be given. Take the certificate and any waivers with you on your trip. You may need it to enter your destination country or get back home. This certificate is valid for 10 years, and some countries are starting to accept it as valid for life. Yellow fever vaccine is only given at authorized U.S. yellow fever vaccine clinics, so you will need to check well in advance. CDC can help you find a place to get yellow fever vaccine (

The first line of defense against illness transmitted by insects is prevention of bites (see "What can I do to avoid insect bites?").

Medically Reviewed by a Doctor on 8/19/2015


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