METHOD: We estimated the two conditions for a Zika outbreak emergence in Southeast Asia: (i) the risk of Zika introduction from Latin America and the Caribbean and, (ii) the risk of autochthonous transmission under varying assumptions on population immunity. We also validated the model used to estimate the risk of introduction by comparing the estimated number of Zika seeds introduced into the United States with case counts reported by the Centers for Disease Control and Prevention (CDC).
RESULTS: There was good agreement between our estimates and case counts reported by the CDC. We thus applied the model to Southeast Asia and estimated that, on average, 1-10 seeds were introduced into Indonesia, Malaysia, the Philippines, Singapore, Thailand and Vietnam. We also found increasing population immunity levels from 0 to 90% reduced probability of autochthonous transmission by 40% and increasing individual variation in transmission further reduced the outbreak probability.
CONCLUSIONS: Population immunity, combined with heterogeneity in transmission, can explain why no large-scale outbreak was observed in Southeast Asia during the 2015-16 epidemic.
METHODS: The PubMed database was accessed to source relevant literature, using combinations of pertinent search terms. Only articles published in the English language were selected. Reference lists of published articles were also examined for relevant articles.
RESULTS: With regard to preferred destinations, South/Central America and the Caribbean were more likely to receive tourists looking for casual sex. Longer duration of travel, travelling alone or with friends, alcohol or drug use, being younger and being single were factors associated with higher levels of casual sex overseas. The majority of literature retrieved on sex workers focused on risk behaviours, sexually transmitted infections (STI), mobility of sex workers and how these factors affected their lives. Sex tourists require better access to effective methods of preventing HIV, such as pre-exposure prophylaxis, and better education on HIV prevention. Drugs and alcohol play a major role as risk factors for and cofactors in casual sexual behaviour while abroad.
CONCLUSIONS: Travellers need to be informed of the increased risks of STI before travel. They should be aware of the local prevalence of STIs and the risks associated with their sexual practices when they travel, including engaging with commercial sex workers, having unprotected sexual intercourse and becoming victims of sexual violence.