ATLANTA – The risk of dengue remains a concern for residents of the United States who travel to the tropics, and the disease burden may be underestimated, surveillance data suggest.
Between 2005 and 2010, 1,697 laboratory-positive cases were reported to the Centers for Disease Control and Prevention’s arbovirus surveillance system (ArboNET) and/or to the CDC dengue branch, for an annual average of 285 cases. A substantial number of cases occurred in New York City and in Florida, and most travelers failed to take precautionary measures when traveling to endemic areas, according to data presented at the International Conference on Emerging Infectious Diseases.
CDC/James Gathany
World travelers should minimize mosquito exposure as dengue remains a legitimate concern for those headed to the tropics.
Furthermore, when the estimated number of cases derived from laboratory testing data was compared with the number of laboratory-positive cases, there was a fourfold degree of underreporting, Dr. D. Fermin Arguello of the CDC, San Juan, Puerto Rico reported in a poster at the conference.
The CDC data indicated that half of the cases occurred in travelers to the Dominican Republic, Puerto Rico, India, Mexico, or Haiti.
Data from the New York City Department of Health and Mental Hygiene showed that between 2001 and 2009 the annual average was 36 cases, but that in 2010, when a global dengue epidemic occurred, 144 cases were identified, according to Brooke Bregman of the department.
This was more than any other single year, she pointed out.
Cases in New York also frequently occurred in travelers to the Dominican Republic and Puerto Rico. In fact, most cases there (68%) were associated with travel to the Caribbean. Others were associated with travel to Southeast Asia (13%), and South America (10%), Ms. Bregman said.
The New York data indicated that, although 81% of patients recalled being bitten by mosquitoes, only 29% reported using mosquito repellent and only 14% used a bed net.
Only 10% sought medical advice before traveling, Ms. Bregman said, noting that effective strategies are needed to encourage travelers to adopt protective measures.
Dr. Arguello agreed, noting also that travelers should seek pre-travel consultation, minimize mosquito exposure while traveling, and seek medical attention if they develop a fever either during travel or soon after return from travel.
He also noted a need for improvements in national surveillance reporting to determine the risk and impact of dengue in U.S. travelers.
In another poster presented at the conference, researchers noted that educational strategies do have a beneficial impact.
A 2011 population-based evaluation of knowledge, attitudes, and behaviors toward dengue prevention in Key West showed that of 526 households evaluated, more than 80% were able to identify infected mosquitoes as the transition mode for dengue, and standing water as an important source for the mosquito vector, according to Emily Zielinski-Gutiérrez, DrPH of the CDC, Fort Collins, Colo.
Respondents who reported being exposed to dengue educational messages were significantly more knowledgeable about the disease than were those with no recall of exposure to such messages, according to scores on a dengue knowledge scale, she said.
The Florida Keys Mosquito Control District and local newspaper articles were the most frequently cited sources of information about dengue.
This study highlighted areas where more effort is needed, however; less than half of the respondents were aware that some patients in Key West had been hospitalized for dengue, and a third could not name specific symptoms of dengue illness, Dr. Zielinski-Gutiérrez reported.
None of the authors had disclosures to report.