The bacteria that causes it—spirochete bacteria of the genus Leptospira—infect rats, which shed the bacteria in their urine.
Between 2001 and 2020, the city logged an average of just three leptospirosis cases a year—and some of those were travel related.
In 2023, there were 24 cases, the highest number of cases ever recorded for a single year.
That number of cases so far this year is concerning given that Leptospira bacteria are “fragile,” as the NYC health department puts it.
The health department noted that climate change, which is causing excessive rain and unseasonably warm temperatures, may be partly driving the uptick in cases.
The cases are typically related to living or working in environments with rat urine, contaminated soil and water, or materials frequently contaminated with rat urine, such as trash bags or food waste bins.
The health department noted that human-to-human transmission is rare.
New York isn’t the only city plagued by leptospirosis cases.
Following a record number of cases last year in New York City due to a potentially fatal bacterial infection typically spread by rat urine, the NYC Department of Health and Mental Hygiene reports that this year is expected to set a new record.
Leptospirosis is the infection, and it can cause a variety of symptoms, including general ones like fever, chills, headache, and muscle aches, as well as vomiting, diarrhea, and cough. However, if treatment is not received, the condition may worsen and result in liver damage, kidney failure, bleeding, jaundice, conjunctival suffusion (bloody eyes), breathing difficulties, and even death.
Rats are infected with the bacteria that causes it, spirochete bacteria of the genus Leptospira, which they excrete in their urine. Contact with open wounds or mucous membranes directly transfers the germs to humans.
There are an estimated 3 million rats living in New York City, and the city has long been engaged in a losing battle with them. Fighting the rat population has become a top priority for Mayor Eric Adams, and the city council just last week suggested using salty pellets as birth control to reduce the number of furry brown rodents living in the colony.
Nevertheless, until recently, leptospirosis was not a major concern resulting from the rats’ mischievous behavior. In just three leptospirosis cases annually on average between 2001 and 2020, some of which were linked to travel. However, during the pandemic, things changed as it appeared that the rat population was growing. The average increased to 15 between 2021 and 2022. The greatest number of cases ever reported for a single year was 24, which occurred in 2023. Furthermore, as of April 10, there had been six cases reported.
Considering that Leptospira bacteria are “fragile,” as the NYC health department describes them, the number of cases this year to date is concerning. Both the dry heat of summer and the freezing temperatures of winter cause them to perish quickly. Their primary growth period is in warm, humid environments. June and October of last year were the months with the highest number of cases. The health department stated that the increase in cases might be partially attributed to climate change, which is bringing on excessive rain and unusually warm temperatures.
The city’s health department issued a health advisory last week, advising physicians to be alert for cases. Common oral antibiotics are used to treat mild cases, while intravenous doses are used for severe cases. after an exposure, symptoms usually appear 5 to 14 days later, though they can appear as late as 2 to 30 days eventually.
Out of the 98 locally acquired cases that the city has documented between 2001 and 2023, men accounted for 94% of the cases, with a median age of 50 and a range of 20 to 80 years. The Bronx had the highest number of cases (37), followed by Manhattan (28), Brooklyn (19), Queens (10), and Staten Island (4). Patients with severe respiratory involvement, liver and kidney failure, and sometimes both were brought to the attention of physicians. Six of the 98 cases resulted in death.
The cases usually have to do with rat urine-contaminated soil and water, rat urine-contaminated materials (like trash bags and food waste bins), or rat urine-contaminated living or working environments. It is uncommon for human-to-human transmission, according to the health department.
Not just New York is experiencing an epidemic of leptospirosis cases. Doctors in the Netherlands reported a case last year involving an 18-year-old who had fallen into a canal that was probably tainted with rodent urine, resulting in leptospirosis and jaundiced, bloodshot eyes.
