From 1973 through 1983, 2,575 cases of malaria were reported
among
U.S. citizens who were infected while traveling abroad. This was
33%
of all imported cases reported during this period--the majority
occurring among foreign nationals. Of the cases among U.S.
citizens,
849 (33%) had been infected with Plasmodium falciparum. During
this
period, the number of P. falciparum infections among U.S. travelers
rose almost sevenfold from 21 cases in 1973 to 139 in 1983. The
increase has been especially marked among U.S. travelers who
visited
east Africa: in 1973-1974 only nine cases occurred among such
travelers, compared with 88 cases in 1982-1983 (a nearly 10-fold
increase). Infections with P. falciparum malaria in nonimmune
individuals can be extremely serious and potentially fatal: 31
deaths
from malaria occurred among the 849 patients with P. falciparum
infections, for a case-fatality ratio of 4%.
In 1982-1983, more than half of all P. falciparum cases in the
United States were imported from five countries: Kenya (61 cases),
Haiti (26), Tanzania (19), Nigeria (15), and Ghana (10); 167 (68%)
of
the 247 P. falciparum infections among U.S. travelers were acquired
in
Africa. Attack rates for certain years can be estimated for Kenya,
Ghana, and Haiti based on the number of U.S. travelers to those
countries as provided by the World Tourism Organization in Madrid.
The estimated number of malaria infections in U.S. travelers to
Kenya
increased from 21.2 per 100,000 travelers in 1977 to 83.3/100,000
in
1982; for Ghana, the estimated number of malaria infections was
104.4/100,000 U.S. visitors in 1977-1978; for Haiti, the number was
19.2/100,000 in 1982.
Importation of malaria is not only a problem in the United
States. For instance, the number of imported cases of malaria into
Great Britain increased from 100 in 1970 to 1,471 in 1982. Between
1970 and 1980, 88% of the P. falciparum infections reported in
Great
Britain originated in Africa (1).
Travelers who acquire malaria generally do not take appropriate
chemoprophylaxis. For example, only 8% of the U.S. travelers who
acquired P. falciparum malaria in west Africa or Haiti between 1981
and 1983 had histories of having taken chloroquine chemoprophylaxis
during their travels. Reduced efficacy of chemoprophylaxis may
also
factor in the increased importation of malaria from certain areas,
especially east Africa: the percentage of patients who reportedly
had
used chloroquine as chemoprophylaxis while traveling in east Africa
increased from 22% in 1977 to 76% in 1983. This trend has been
reviewed recently by CDC and has necessitated changes in
recommendations for chemoprophylaxis for U.S. travelers to defined
areas of east Africa (2).
Reported by Malaria Br, Div of Parasitic Diseases, Center for
Infectious Diseases, CDC.
Editorial Note
Editorial Note: The risk of malaria to travelers can be reduced
through adequate use of effective chemoprophylactic drugs. This
requires that travelers to malarious countries be adequately
informed
about malaria risks and malaria chemoprophylaxis and that they be
motivated to adhere to recommendations. Information about health
risks and chemoprophylaxis is provided through official
publications
from CDC (3,4) and the World Health Organization (5). Little is
known, however, about traveler awareness of the risk in malarious
areas, about the advice, if any, they receive about
chemoprophylaxis
and from which sources, and whether some categories of travelers
(e.g., missionaries, Peace Corps volunteers) may be better informed
than other groups (e.g., tourists, business travelers). Because of
the large number of U.S. international travelers and the great
diversity in the U.S. travel industry, efficient dissemination of
information to help protect the health of the traveling public is
difficult.
In increasing areas of the world, chloroquine can no longer be
considered an effective drug to prevent P. falciparum malaria.
Chloroquine-resistant P. falciparum is known to exist in the
following
countries: Bolivia, Burma, Burundi, Colombia, Comoros, Ecuador,
French Guyana, Kampuchea, Kenya, Laos, Madagascar, Malaysia, Papua
New
Guinea, Rwanda, Solomon Islands, Surinam, Tanzania, Thailand,
Uganda,
Vanuatu, Venezuela, Vietnam, and in parts of Bangladesh, Brazil,
China, India, Malawi, Mozambique, Panama, Peru, the Philippines,
Sudan, Zaire, and Zambia. Weekly use of the combination drug,
pyrimethamine-sulfadoxine (FansidarR), in addition to weekly use of
chloroquine, is recommended by CDC for travelers to these areas
(5).
An update of CDC's recommendations (2) regarding
chemoprophylaxis
will be published soon as an MMWR Supplement, "Prevention of
Malaria
in Travelers, 1984."
References
Bruce-Chwatt LJ. Imported malaria: an uninvited guest. Br
Med
Bull 1982;38:179-92.
CDC. Prevention of malaria in travelers, 1982. MMWR
Supplement
1982;31:1S-28S.
CDC. Health information for international travel, 1983.
Atlanta,
Georgia: Centers for Disease Control, 1983; HHS publication
no.
(CDC) 83-8280.
World Health Organization. Vaccination certificate
requirements
for international travel and health advice to travellers.
Geneva,
Switzerland: World Health Organization, 1983.
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