Systematic Hospital-Based Travel Screening to Assess Exposure to Zika Virus

We queried hospital patients about international travel in the previous 30 days to assess potential importation of emerging infections. We used 12 months of deidentified data to analyze patient demographics, travel destinations, and diagnoses for exposure to Zika virus. Our approach could be used to analyze potential infectious disease exposures.

1 Preliminary results were presented at the 65th Annual Meeting of the American Society of Tropical Medicine and Hygiene, Atlanta, Georgia, November 12-17, 2016.
We queried hospital patients about international travel in the previous 30 days to assess potential importation of emerging infections. We used 12 months of deidentified data to analyze patient demographics, travel destinations, and diagnoses for exposure to Zika virus. Our approach could be used to analyze potential infectious disease exposures.
patients who had complete demographic, destination, and diagnostic data, 3,109 (62.1%) were female and 1,895 (37.9%) male; patients were 10 months-94 years of age. A total of 959 (19%) were evaluated in the ED/WIC, and 161 (3.2%) with recent travel were hospitalized. The most frequently visited destinations were Canada, the United Kingdom, and Mexico (Table 1).
When analyzed for destinations in WHO categories 1-3 (11), 1,492 travelers, 963 female and 529 male, visited 1,570 destinations with ZIKV transmission. Mexico, the Dominican Republic, Aruba, Brazil, and Costa Rica (Table 1) were the most frequently visited destinations, and the Caribbean was the most frequently visited region (n = 648).
Among patients who traveled to countries with ZIKV transmission whose admitting diagnosis or description was available, 42 listed symptoms compatible with ZIKV infection (  identify Guillain-Barré syndrome or any complications of pregnancy among the 42 patients, but 2 had laboratory-confirmed ZIKV infection. Our results approximate the Global Travel Epidemiology Network analysis of pretravel consultations (13), in which 28% of 22,736 travelers planned trips to ZIKV-affected countries and >75% were of reproductive age. Another study retrospectively reviewed 46 patients for possible ZIKV infection and found 17% had laboratory evidence of infection (14). Applying this seropositivity rate to our study, if testing had been done, 7 patients with symptoms compatible with ZIKV clinical criteria might have had laboratory-confirmed ZIKV infection.
We found that a standardized question to screen for international travel provided a description of travel patterns for this patient community. Data from the 12-month period coincided with the rapid spread of ZIKV and revealed the sizable portion of patients who might have been exposed to ZIKV during travel. Population-based analysis of travelrelated ZIKV exposure could provide estimates of at-risk populations and diagnostic testing needs, especially for pregnant women. The application is especially promising with newer electronic health record systems. However, limited testing capability might have underestimated the actual number of travel-associated cases (15), even when clinicians suspected ZIKV. Our study had some limitations. Because we only reviewed the population at 1 hospital during a single 12-month period, our results might not be generalizable to the US population. Our analysis relied on recent travel to countries and territories that reported ZIKV transmission, but some travelers might have visited risk-free settings, such as locations at higher altitudes, resulting in overestimation of the number of possible infections. Infectious ZIKV has been detected in semen mainly <30 days after fever onset, but its presence in semen has been documented longer (10,15); therefore, the potential number of ZIKV infections might exceed our estimate because sexual partners could become infected. Also, we did not have information on whether the patients of reproductive age were sexually active, fertile, had pregnant partners, or were planning conception. We might have missed cases for the following reasons: we relied on diagnoses and diagnostic descriptions, but omission of symptoms in these fields might not represent truly absent symptoms; some infected persons might have been unaware of ZIKV and might not have sought medical evaluation; the incubation period of sexually transmitted ZIKV might be >30 days and patients might have become ill after being seen; we did not collect or record ZIKV infections identified after the study period; only patients strongly suspected of ZIKV were tested due to limited laboratory capacity; and the travel screening question would not have identified sexually transmitted ZIKV infection in a patient who had not traveled internationally.

Conclusions
We used a systematic travel screening question to analyze potential exposure to ZIKV in a hospital population. Because up to 80% of ZIKV infections are asymptomatic (2), we used travel to Zika-affected countries as a proxy for potential ZIKV exposure. In patients with international travel <30 days before seeking treatment, 31.4% visited countries with ZIKV transmission. Half of the female patients and most male patients were of reproductive age. In this population, 30% of female patients who were of reproductive age or pregnant reported travel with potential exposure to ZIKV; male patients similarly were affected. Despite severe restrictions on testing for ZIKV infection at the time of the study, our analysis demonstrated the ability to identify patients with clinical findings that fit the ZIKV case definition even if they were not tested. We also identified a large proportion of patients who should have received Zika pretravel counseling.
Analysis of the hospitalwide data for recent travel history provided a tool to assess the proportion of the population that might have been exposed to ZIKV. These data could inform population-based ZIKV vaccination needs in the future. In addition, systematic travel screening also could be applied to other imported emerging infections in the future.