Hospitalization rates from leptospirosis have remained low in the United States since the late 1990s, but federal health investigators say clinically diagnosed cases of the bacterial infection may be underreported.
To get a better idea of the disease’s US prevalence, the investigators analyzed hospital discharge data from 1998 to 2009 in the Nationwide Inpatient Sample, the largest all-payer inpatient care database in the country.
The average annual rate of leptospirosis-associated hospitalizations was 0.6 hospitalizations per 1 million population during the study period. But the investigators noted that tracking hospitalizations is a passive means of surveillance compared with tracking reported cases. Previous studies have indicated that active surveillance can identify 5 times more leptospirosis cases than passive surveillance, which also detects only about one-third as many hospitalizations as does active surveillance. Consequently, cases may be underreported (Traxler RM et al. Emerg Infect Dis. doi:10.3201/eid2008.130450 [published online July 16, 2014]).
Reemerging Leptospirosis May Be Underreported in the United States. JAMA. 2014;312(9):884. doi:10.1001/jama.2014.10414