HOUSTON - October 31, 2000-Vaccination for typhoid fever should be considered for even short-term visits to high-risk areas, Dr. Ellen Steinberg said at the annual meeting of the American Society for Tropical Medicine and Hygiene.
"In 1994, the Advisory Committee on Immunization Practice published guidelines for typhoid immunization which recommend typhoid vaccination for travelers to areas in which there is a recognized risk of exposure to Salmonella Typhi, the bacteria that causes typhoid fever. They note that the risk is greatest for travelers to developing countries who have prolonged exposure to contaminated food and drink. The data that we have from typhoid cases in the US between 1994 and 1999 indicate that approximately half of the cases occurred in travelers who had traveled for 4 weeks or less," said Dr. Steinberg, of the Foodborne and Diarrheal Diseases Branch, National Center for Infectious Disease, Centers for Disease Control and Prevention.
Travelers to the Indian subcontinent, including Pakistan and Bangladesh, appear to be at particular risk, based on an analysis of all typhoid fever cases reported to the CDC's National Typhoid Fever Surveillance System between 1994 and 1999. During this period there were 1,166 cases of laboratory-confirmed cases of acute Salmonella typhi infection reported in 41 states and 22 territories. The median age of the affected individuals was 22, with a range from 3 months to 94. Among these, only 27 people (3%) reported being vaccinated prior to travel.
Travel to six countries accounted for 70% of the cases. Among all the cases, 30% occurred in travelers to India, 13% in travelers to Pakistan, 10% in travelers to Mexico, 6% in travelers to Bangladesh, and 6% in travelers to Mexico.
Among the 150 affected persons who reported reasons for travel, 77% of the infections occurred in people visiting family, 14% in people immigrating to the United States, 9% in tourists, and 3% in business travelers.
"More than half the cases occurred in travelers age 22 or younger which suggests that we should expand our prevention strategies to reach more children and students", Dr. Steinberg said. Furthermore, more than 7% of the cases occurred in children under age 2. At one time a typhoid vaccine for children aged 6 months to 2 years was available but it is no longer produced, she noted, and there has been no vaccine for infants less than 6 months old. The existing oral vaccine is recommended only for children older than 6. "In the United States, no vaccine is currently being manufactured for use in children who are less than two years of age," she said.
All travelers should reduce their risks by taking certain precautions in areas of the world where food and water may be contaminated. This includes following the advice "boil it, cook it, peel it, or forget it," drinking only bottled or boiled water, and avoiding foods and beverages from street vendors. Further information for travelers is available at http://www.cdc.gov/travel/typhoid.htm.
The purpose of this study was to gather as much data as possible to clarify the indications for typhoid immunization and to identify groups that could benefit from improved prophylactic measures, such as new vaccines, she said.
Infection with Salmonella typhi causes an estimated 16 million cases of typhoid fever worldwide each year, including 200-400 travel-associated cases in the United States.
The American Society of Tropical Medicine and Hygiene (ASTMH) is the principal organization in the United States representing scientists, clinicians, and others with interests in the prevention and control of tropical diseases through research and education. Additional information on the meeting can be found at http://www.astmh.org/presskit.html.