Abstract
We examined New York City Department of Health and Mental Hygiene surveillance data on hepatitis A, malaria, and typhoid to determine the proportion of these diseases related to travel and their geographic distribution. We found that 61% of hepatitis A cases, 100% of malaria cases, and 78% of typhoid cases were travel related and that cases clustered in specific populations and neighborhoods at which public health interventions could be targeted. High-risk groups include Hispanics (for hepatitis A), West Africans living in the Bronx (for malaria), and South Asians (for typhoid).
Travel to developing countries is associated with hepatitis A, malaria, and typhoid infection, and travelers who are visiting friends and relatives are at considerably higher risk than are tourists of acquiring these diseases.1–3 Diseases acquired during travel are problematic in New York City (NYC) because the percentage of immigrants residing in the city, with 36% of residents born abroad, is approximately 3.5 times the national percentage. In addition, NYC residents account for 12% of US air travelers to overseas destinations while representing only 3% of the US population.4–6
Using data collected by the NYC Department of Health and Mental Hygiene, we assessed the burden of hepatitis A, malaria, and typhoid (3 diseases targeted by the US Department of Health and Human Services with respect to prevention efforts7) carried back to the city by travelers. We focused on people who had traveled to visit friends and relatives in their home countries in an attempt to determine whether particular high-risk groups (as well as particular areas of NYC) should be targeted for prevention interventions. We classified travelers visiting friends and relatives as immigrants who were ethnically or racially distinct from the majority population of the United States and who returned to their homeland to visit friends or relatives.2,8
METHODS
We used SAS version 9.1 (SAS Institute Inc, Cary, NC) to analyze hepatitis A data from July 5, 2005, through December 31, 2006 (18 months); malaria data from January 1, 2004, through December 31, 2006 (36 months); and typhoid data from January 1, 2000, through December 31, 2005 (72 months). GIS ArcMap version 9.2 (ESRI, Redlands, CA) was used to create maps indicating the geographic locations of cases. We calculated NYC incidence rates using US Census Bureau's 2005 intercensal population estimates.9 For each variable assessed, we calculated percentages using as the denominator the number of patients for whom data for that variable were available. Data on durations of hospitalization for malaria cases reported between 2004 and 2006 were obtained from the NYC Health and Hospitals Corporation (J. Goldstein, MPA, New York City Health and Hospitals Corporation, written communication, November 2007).
A case was considered travel related if the patient was outside the 50 US states for the usual incubation period of each disease. The travel status “visiting friends and relatives” could not be determined for cases of hepatitis A because the questionnaire did not specifically ask for purpose of travel or country of birth. A malaria case was classified as obtained while visiting friends and relatives if the patient had stated that his or her main purpose of travel was to visit friends or relatives. A typhoid case was classified as obtained while visiting friends and relatives if the infection was acquired in the patient's country of birth.
RESULTS
Table 1 reports incidence rates for each of the diseases by city borough, demographic characteristics, and hospitalization data. Figure 1 displays the geographic locations of cases. Maps of all cases, travel-related cases, and cases obtained while visiting friends and relatives displayed similar geography throughout NYC.
TABLE 1.
Incidence Rates, Demographic Characteristics, and Hospitalization Data: Travel-Related Hepatitis A, Malaria, and Typhoid in New York City, 2000–2006
| Hepatitis A | Malaria | Typhoid | |
| US rate per 100 000 population (200510) | 1.5 | 0.51 | 0.11 |
| Total no. of cases, New York City | 251 | 558 | 254 |
| Rate per 100 000 residents, New York City | 2 | 2.3 | 0.52 |
| Rate per 100 000 residents, by borough (no. of cases) | |||
| Bronx | 2.5 (52) | 4.3 (74) | 0.34 (28) |
| Brooklyn | 1.9 (71) | 2.1 (159) | 0.35 (54) |
| Manhattan | 1.7 (42) | 1.5 (102) | 0.35 (34) |
| Queens | 2.5 (83) | 1.5 (101) | 0.97 (131) |
| Staten Island | 0.4 (3) | 1.5 (22) | 0.25 (7) |
| Cases related to travel, % | 61 | 100 | 78 |
| Travel-related cases among women, % | 54 | 30 | 44 |
| Mean age, y, of patients with travel-related cases (median) | 21 (16) | 35 (37) | 21 (17) |
| Patients with travel-related cases hospitalized, % | 38 | 72 | 86 |
| Mean duration of hospitalization, d, among patients with travel-related cases (range) | 3.8 (1–8) | 3.6a (1–27) | 8.2 (1–30) |
| VFR patients among travel-related cases, % | … | 76 | 63 |
| Female VFR patients, % | … | 27 | 39 |
| Mean age, y, of VFR patients (median) | … | 35 (38) | 26 (23) |
| VFR patients hospitalized, % | … | 73 | 88 |
| Mean duration of hospitalization, d, among VFR patients (range) | … | … | 7.8 (1–30) |
Note. VFR = visiting friends and relatives.
Data were obtained from the New York City Health and Hospitals Corporation for cases of malaria between 2004 and 2006 (J. Goldstein, written communication, November 2007).
FIGURE 1.
Maps depicting geographic locations of travel-related disease cases by (a) hepatitis A, (b) malaria, and (c) typhoid: New York City, 2000–2006.
Hepatitis A
There were 251 cases of hepatitis A. Travel status was known for 234 cases, of which 143 (61%) were travel related. Ethnicity was known for 131 of these cases, and Hispanics accounted for 74 of the 131 cases (56%). The rate among Hispanics was 4.0 per 100 000 NYC residents, as compared with 1.1 per 100 000 among non-Hispanics. Among travelers reporting their destination (n = 134), 92 (69%) had traveled to the Caribbean or South or Central American countries. Three countries, the Dominican Republic, Ecuador, and Mexico, accounted for 69 (51%) of the destinations. Hepatitis A was distributed across all of the city's boroughs, with the Bronx having the highest rate. Only 4 patients reported a history of hepatitis A vaccination before travel.
Malaria
All 558 malaria cases were travel related. Reason for travel was known for 476 cases, of which 363 (76%) were classified as obtained while visiting friends and relatives. Four hundred twenty (75%) cases were acquired in West Africa, with Nigeria and Ghana accounting for more than half of those acquisitions (n = 280). The incidence of malaria in the Bronx was twice that of other boroughs. Antimalarial prophylaxis was taken by 102 (18%) malaria patients overall and by 60 (17%) patients with cases classified as obtained while visiting friends and relatives.
Typhoid Fever
There were 254 cases of typhoid fever. Travel status was known for 225 cases, of which 175 (78%) were travel related. Country of birth was also known for 160 of these cases, with 110 (63%) classified as obtained while visiting friends and relatives. Seventy-five (68%) patients classified as visiting friends and relatives contracted typhoid in Bangladesh, India, or Pakistan. The incidence of typhoid in Queens was nearly 3 times that of other boroughs. Two of the patients with travel-related cases reported receiving typhoid vaccine.
DISCUSSION
Our data confirm that NYC bears a disproportionate burden of hepatitis A, malaria, and typhoid cases compared with reported national US rates for these diseases; they also corroborate previous research findings that these diseases are frequently associated with travel and focused in specific populations.1,2,11 Furthermore, our findings demonstrate that, within NYC, these diseases are concentrated in distinct high-risk populations and areas. For example, the rate of hepatitis A among NYC Hispanics is 3 times that of non-Hispanics; malaria rates are highest in northern Manhattan and the Bronx, at approximately 8 times the national rate; and the typhoid rate in Queens is nearly triple that of the other NYC boroughs.
If anything, we suspect that the burden may be larger than observed here because of the systemic underreporting common in surveillance studies. We suspect that such underreporting is more frequent among patients visiting friends and relatives because they may be disenfranchised or less willing to access the medical system for certain conditions (e.g., fever due to typhoid) unless they are very ill.
It has been shown that travelers, particularly travelers visiting friends and relatives, receive poor medical preparation for international travel for myriad reasons.11–13 For instance, primary health care workers do not always provide appropriate education, medications, or vaccines to travelers.3,12,14 In addition, travelers visiting friends and relatives are less likely than are tourist travelers to seek pretravel health advice.2 In a study conducted at NYC's John F. Kennedy International Airport, 22% of individuals traveling to the developing world were unaware of the need for pretravel health advice and vaccinations, and 20% did not perceive a risk of infection.13 The costs associated with obtaining travel health advice or purchasing vaccines and medications were reported as deterrants.12
Furthermore, many travelers, in particular travelers visiting friends and relatives, may not adhere to advice on how to avoid disease and may decline medications or vaccines as a result of perceived exaggerated concerns about risks or their belief that they know how to protect themselves from illness.12,13 Although vaccines and prophylaxis are not 100% effective and travelers can still fall ill, the low vaccination and prophylaxis rates among returning travelers in our study suggest that travel information and prophylactic measures are not being disseminated or advice is not being followed.
Compounding these issues is the fact that travelers visiting friends and relatives are members of a subgroup of the US population that typically receives less health care than other groups.4 Foreign-born US residents are less likely to have health insurance and have lower levels of vaccination than are US-born residents.4,15 According to the 2000 census, uninsurance rates were 22%, 21%, and 19% in the Bronx, Brooklyn, and Queens, respectively, whereas uninsurance rates were between 7% and 15% in all other counties of New York State.16 As a possible example of the effects of this disparity, the majority of cases of hepatitis A have been shown to occur among Hispanic travelers and immunization levels are lower for Hispanic than non-Hispanic children.17
Treating these diseases imposes a considerable financial burden on NYC's health care system. Given the $1660 mean daily cost of a non–intensive-care-unit bed at a NYC Health and Hospitals Corporation hospital (i.e., public hospital) in 2007 (E. Brenner, BS, New York City Health and Hospitals Corporation, written communication, January 2008) and our length of stay data, the estimated annual cost associated with inpatient treatment (excluding intensive-care-unit, outpatient, and indirect expenses) for travel-related cases of hepatitis A, malaria, and typhoid in NYC would be $1 291 065.
We suggest targeting efforts to prevent these diseases in the high-risk areas and populations identified in our data. Interventions might include educating primary care providers and pharmacists in the identified areas, providing education about avoidance measures for travel-related illnesses in schools, and mandating that travel agents in these areas (as well as low-cost Internet services that cater to these populations) explain the need for education and vaccinations when selling tickets to high-risk destinations. Targeting the NYC populations demonstrated to be at the highest risk for hepatitis A, malaria, and typhoid would provide an opportunity not only to prevent these diseases but also to improve the health of these underserved communities.
Human Participant Protection
No protocol approval was needed for this study.
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