1732 • CID 2001:32 (15 June) • TRAVEL MEDICINE
T R AV E L M E D I C I N EI N V I T E D A R T I C L E
Charles D. Ericsson and Robert Steffen, Section Editors
Travel and the Introduction of Human
Immunodeficiency Virus Type 1 Non-B Subtype
Genetic Forms into Western Countries
Michael M. Thomson and Rafael Na ´jera
A´rea de Patogenia Viral, Centro Nacional de Biologı ´a Fundamental, Instituto de Salud Carlos III, Madrid
Both high mutation rates and recombination contribute to the genetic diversity of human immunodeficiency virus type 1
(HIV-1). Among viruses of the main group, which are responsible for the HIV-1 pandemic, 21 circulating genetic forms have
been reported, 11 of which are recombinant between ?2 subtypes. In Western Europe and the Americas, the HIV-1 epidemic
is largely dominated by B subtype viruses; however, infections with diverse non-B subtype genetic forms are increasingly
being recognized. In Western Europe and North America, most of them have been identified in immigrants or travelers
returning from areas with high HIV-1 prevalence, mainly from sub-Saharan Africa and Southeast Asia, where non-B subtype
genetic forms predominate, but propagation within other groups has been reported in some Western countries. This may
have implications for prophylactic and therapeutic strategies and, by bringing in contact different genetic forms, may favor
the generation of novel recombinant viruses. Travelers from different categories—including immigrants, military personnel,
seamen, tourists, expatriates, diplomats, and businessmen—may be at risk of transporting HIV non-B subtype genetic forms
to Western countries.
An association between AIDS/HIV infection and travel was
already noticed among the earlier cases in the epidemic in
Western Europe: HIV type 1 (HIV-1) infection among homo-
sexual men was found to correlate with sexual exposure to men
in the United States ,and heterosexuallyacquiredAIDScases
were associated with origin from or travel to Central Africa.
In fact, the first cases of HIV-1 infection documented to have
been present in Europe were those of a Norwegian family—a
seaman (who was probably infected in the early 1960s by het-
erosexual contact in a West African seaport), his wife, and his
daughter, all of whom died in 1976 . The relative risk of
acquiring HIV-1 during travel by heterosexuals residing in the
United Kingdom in 1986 was estimated to be 300-fold greater
during a period of time abroad than in the same period of time
Received 18 December 2000; revised 9 February 2001; electronically published 21 May
Reprints or correspondence: Dr. Rafael Na ´jera, Centro Nacional de Biologı ´a Fundamental,
Instituto de Salud Carlos III, Ctra. Majadahonda-Pozuelo, Km. 2, 28220 Majadahonda, Madrid,
Clinical Infectious Diseases2001;32:1732–7
? 2001 by the Infectious Diseases Society of America. All rights reserved.
in the United Kingdom . In sub-Saharan Africa, travel has
also been associated with HIV-1 propagation, as illustrated by
the high prevalence of HIV-1 infection documented among
long-distance truck drivers  and expatriate migrant workers
. Increase in international travel in the last several decades,
in great part facilitated by the expansion of commercial pas-
senger air transport, has contributed in a determinant way to
the rapid dissemination of HIV-1 around the world.
The association of travel with HIV infection largely reflects
the long-recognized link of travel with the risk of acquiring
sexually transmitted infections. Travel may involve changes in
sexual behavior, including an increase in sexual promiscuity
and contacts with prostitutes , among whom, in some areas,
particularly sub-Saharan Africa, Southeast Asia, and India,
where HIV-1 is mainly transmitted heterosexually, the preva-
lence of HIV-1 infection may be remarkably high. Also con-
may be the lower availability of condoms in some developing
countries and injections by unqualified medical staff using im-
properly sterilized equipment, as has been reported among ex-
patriates in sub-Saharan Africa .
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TRAVEL MEDICINE • CID 2001:32 (15 June) • 1737
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