Figure 3. Phylogenetic analysis of mitochrondrial (mt) DNA from nonhuman primates and humans. mtDNA was amplified and sequenced from the simian foamy virus-infected person (BH66), 2 human controls (Hu702 and Hu715), M. mulatta (Rh15454, 18511,18512, 18513,18514,18515, 11363, 9649), M. fascicularis (BP2, 4, 5, 6), M. nemestrina (P46), M. tonkeana (P18,39,40), M. maura (P44, 73), M. nigra (P79, M1); M. nigrescens (M27, 28), and M. hecki (M7). The mtDNA tree was created with the neigh- bor-joining method with the Phylip program (DNAdist; Neighbor). Bootstrap replicates were 1,000. Bootstrap values were calculated by using Seqboot, DNAdist, Neighbor, and Consense (PHYLIP programs). Bootstrap values >60% are shown. The mtDNA tree was plotted in Treeview. This analysis suggests that BH66 was of human origin. Although the phylogenetic tree constructed with mtDNA from a variety of monkey samples can be used to distin- guish human from monkey mtDNA, a large number of nuclear mtDNA sequences, have evolved as pseudogenes (36). These sequences can be highly divergent from mtDNA and resulted in some ambiguity as mtDNA amplified from several monkeys did not group with other members of the same species. Because of the nature and variability of these sequences, definitive conclusions about mtDNA phylogenies could not be determined; however, mtDNA trees were still useful for determining the origin of mtDNA material. liver transplants in 1994, and SFV was detected in the blood and tissues of both at autopsy (39). More research in this area is needed. Moreover, little is known about the epi- zootiology of SFV among wild primates. Although SFV infection in humans has not culminated in any observable symptoms, SFV strains may differ in their capacity to infect or cause disease in humans. Finally, whether SFV can adapt in humans after transmission and potentially lead to disease needs to be examined. Primate-to-Human Retroviral Transmission in Asia Implications and Recommendations for Public Health The recent SARS epidemic vividly demonstrates how the economic infrastructure and dense population of Asia facilitate the rapid international spread of disease. The combination of large primate reservoirs, prevalent human- primate contact, a growing immunocompromised popula- tion, and advanced infrastructure in Asia increases the likelihood of a primateborne zoonosis emerging on this continent. The demonstration of SFV transmission in the context of a monkey temple in Bali points to a broad public health concern: other enzootic primate infectious agents may cross the species barrier and cause significant morbidity and mortality in human populations. Given our lack of knowledge of the effects of SFV, as well as the poorly defined risk of other primateborne zoonoses, steps should be taken to decrease the risks of cross-species transmission among the many persons who visit these sites. Previous data on both worker and visitor exposure to macaques at monkey temples suggest that human behaviors, especially the practice of feeding macaques, is a risk factor for being bitten or scratched (33,34). We have recommended that monkeys be fed only by specially trained personnel who minimize physical contact with monkeys. Such restrictions have been successfully employed at other monkey forests in Asia. For example, Singapore’s Bukit Timah Nature Reserve has nearly 200 free-ranging macaques (M. fascic- ularis), and in 2002, an estimated 380,000 visitors made use of the reserve’s trail system, yet contact between mon- keys and visitors at Bukit Timah is rare. This finding may be ascribed to the park’s policy, enforced by stiff fines, of prohibiting visitors from feeding macaques. Conclusions This study reports the first case of human SFV infection in Asia and also, for the first time, links natural transmis- sion of SFV to a person to a specific population of pri- mates. Our findings suggest that workers in and around monkey temples can become infected with SFV. By impli- cation, visitors to monkey temples, especially those who are bitten by a macaque, may also be at risk for SFV infec- tion. Because many visitors to monkey temples are inter- national travelers, these findings have ramifications for the potential global spread of primateborne infectious agents. Demonstrating natural cross-species transmission in a con- text that does not involve hunting for bushmeat implies that other contexts of primate-human contact may also facilitate the transmission of simian pathogens. These data point to the need for further research into SFV transmis- sion in other contexts, including pet ownership and per- formance animals, as well as in the diverse geographic areas where humans and primates come into contact. Such research will help describe the overall picture of the Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 7, July 2005 1033