Leptospirosis Outbreak in NYC Has Public Health Officials on Alert

In 2016, officials from the New York City Department of Health estimated that the rat population in America’s largest city might be as high the human one—or roughly 8 million.

While that may be disconcerting to the faint of heart, it also poses a potential public health challenge, as rats, like most living creatures, carry infectious diseases and have been known to attack and bite humans when they feel threatened. In addition, they can pass along diseases more innocently, through their feces and/or urine. In fact, it is believed rats are behind a human outbreak of leptospirosis in the Bronx section of New York, 1 of the 5 boroughs and an area that includes some of the poorest neighborhoods in the United States.

According to an Associated Press report on February 15th, 1 person has died and 2 others have suffered serious illness as a result of the bacterial disease, which is transmitted via rats (through their urine). All 3 cases were confirmed between mid-December and February, and all 3 were reported within a 1-block radius—on the Grand Concourse in the Melrose neighborhood, one of the poorest in the region. The New York City Department of Health confirmed the case cluster in a statement.

“The Health Department has identified a cluster of three cases of leptospirosis on one block in the Concourse area of the Bronx,” said Health Commissioner Mary T. Bassett, MD, MPH, said in the release. “This illness can be serious but is treatable with readily available antibiotics. The Health Department, in partnership with its sister agencies the Housing Preservation and Development and the Buildings Departments, has taken immediate measures to ensure the health and safety of residents by reducing the rat population in the area and is educating tenants about precautions, signs, and treatment.”

According to city health officials, New York City typically sees 1 to 3 cases of leptospirosis annually; however, this is the first time a “case cluster” (multiple localized cases) has been identified. In the statement, they noted that they are working with other city agencies to reduce the rat population in the affected neighborhood and educate local residents about the disease and how to prevent infection. At least 1 of the 3 people infected lived in a building that had signs of rat infestation.

Worldwide, human leptospirosis infections are much more common, particularly in tropical and sub-tropical climates. A recent systematic review estimated that there are more than 1 million cases of—and nearly 60,000 deaths caused by—leptospirosis annually. Although the disease has historically been linked with rats, recent research suggests it may also be transmitted via the urine of dogs and livestock. It can pass to humans through direct contact with the urine of infected animals or through contact with water or soil that is contaminated with infected urine, via the mucous membrane or cuts on the skin. Interestingly, risk for transmission increases due to environmental factors (eg, heavy rainfall/flooding, poor sanitation, and population growth).

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.