This section provides information about which disease exposures are likely in different geographic regions of the world. It is intended to help the clinician provide useful region-specific education and other interventions to prospective travelers and assist in the evaluation of ill returned travelers. Because infectious diseases are dynamic and new microbial threats continue to emerge (1), this chapter cannot accurately reflect the current situation with infections that are changing in distribution, such as H5N1 avian influenza, polio, and chikungunya virus infection (2,3). Regularly updated information and reports of outbreaks can be found on several official websites (e.g., http://wwwn.cdc.gov/travel/ and http://www.who.int/csr/don/en/); not all sites (e.g., ProMED) are verified (4-7). The information is displayed in different ways. Table 3-1 portrays 24 of the more common infections in travelers and allows a quick overview of disease risks for specific pathogens by region. Respiratory tract and diarrheal infections, among the most common infections in travelers, are caused by multiple different pathogens, many with a global distribution. For infections caused by specific pathogens, the level of risk (including history of epidemic activity or high-risk areas) is based on information in local populations. In the summary for each region, important infectious disease risks are described, organized by means of transmission. Those marked by an asterisk (*) within the text have more than one mode of transmission.
The reader should keep in mind that many microbes, such as influenza virus, cytomegalovirus, Epstein-Barr virus, HIV, Toxoplasma, Streptococci, Streptococcus pneumoniae, Salmonella, Neisseria gonorrhoeae, Treponema pallidum (syphilis), Campylobacter, the coliforms causing urinary tract infections, and many others are globally distributed and cause infections in travelers. Travelers may be at increased risk for some of these because of the conditions of travel (e.g., crowding, poor sanitation, and poor air quality) or activities during travel (e.g., sex with new partners) (8). Most of these broadly distributed infections are not described specifically in the regional sections.
Most sections include a comment about more common infections that occur in travelers to the region and also note chronic and latent infections that may be seen in immigrants from the region.
The disease lists are by no means exhaustive. Priority is given to infections that are preventable and treatable. The materials in this section are intended to be used in conjunction with other sections of this book that provide maps and give more details about specific diseases. Other useful materials can be found on the CDC and WHO websites and from other sources.
The data presented here have many limitations. The areas where an infection can be acquired may expand, contract, and shift over time. New diseases are recognized; old ones are sometimes eliminated, although sequelae in individuals may persist after active transmission has ceased. Humans migrate, sometimes carrying pathogens (and potential for transmission) with them. The data on which these descriptions are based may be incomplete, inaccurate, or out of date. Most infectious diseases are not notifiable; even when cases are reported, the data typically reflect only a small fraction of actual cases. Reports may be withheld, delayed, or modified because of concerns about the economic impact of an infectious disease on travel and trade. Maps of disease distribution are usually based on infections in a local population, yet risk of clinical infection (e.g., hepatitis A or diarrhea) in a traveler to a region may be substantially higher than in a local resident (most of whom may be immune) or substantially lower (e.g., ascaris, hookworm, or filariasis) because of living conditions and duration of time spent in the area. Manifestations of the same infection in traveler and local resident may differ because of host factors.
Although we define areas of risk by regions, not all countries within a given region may pose risk for exposure to that infection. For some diseases, risk may exist in only one or two countries within a region or in focal areas within a country. For infections that are designated as having local or sporadic transmission, risk may be absent from much of the region. Distributions of infection typically do not coincide with geopolitical boundaries. Adding to the complexity, countries may be split, boundaries may shift, and names may change, making tracking data about distribution in a particular country over time more difficult.
Ideally, spatial (location of transmission) and temporal (seasons or years of risk) distribution and intensity of transmission would be displayed. Semiquantitative terms, such as common, uncommon, and rare, used to describe risk of infection have different meanings for different people and are used inconsistently. Portrayal of risk is often influenced by the severity or lethality of infection and not just by numbers of cases.
Host factors, duration of stay, accommodations, and specific activities influence types and level of risk. These summaries represent broad generalizations intended to provide some initial guidance to clinicians, who may need to consult other references or websites for more detailed information about distribution (9-14).
