CHICAGO (WGN) – Chicago health officials are sounding the alarm after multiple cases of leptospirosis have been reported.
The Chicago Department of Public Health said a total of six cases have been reported to the department so far this year, which is more than expected.
Officials said median case numbers historically have been two per year.
Leptospirosis is transmitted to human via exposure to infected animal urine, often through contaminated water or soil. The bacteria can survive in water or soil for weeks or months.
Of the six cases reported, four of them were identified as having experienced symptoms between July 16 to Aug. 28. The cases in July and August all reported either direct exposure to animal waste, particularly from rats, or indirect exposure to rodent waste through gardening/yard work; the recent cases have been clustered around the Logan Square and West Town areas, according to officials.
Officials said the majority of cases are mild, but about 10% of cases become severe and life-threatening, including hepatic and renal failure, and in some cases, pulmonary hemorrhage.
The health department said about 100-150 cases of leptospirosis are reported annually in the United States.
Outbreaks are more likely to happen after heavy rain and flooding.
High-risk activities for transmission include swimming or boating in freshwater or floodwater that may be contaminated with animal urine, gardening, yardwork, outdoor cleaning/maintenance, hiking and work or activities that include direct contact with animals or animal urines or other body fluids.
The incubation period after exposure is usually 5-14 days, but may range from 2-30 days.
Most common symptoms include fever, chills, body aches (especially in the calves and lower back), nausea, vomiting, diarrhea, abdominal pain, cough, conjunctival suffusion and sometimes skin rash.
Officials said illnesses may come with two phases, where a patient may briefly recover only to develop severe symptoms afterwards.
About 10% of cases progress to severe disease and symptoms of severe disease include renal failure, pulmonary hemorrhage, jaundice, respiratory failure, meningitis, cardiac arrythmias and circulatory collapse.
Leptospirosis can also cause complications in pregnancy, including spontaneous abortion or fetal death.
From 2015-2025, officials said 28 cases of leptospirosis have been reported in Chicago.
The Chicago Department of Public Health recommends the following:
- Healthcare providers should consider testing patients for leptospirosis or referring patients with high suspicion of illness to a nearby emergency department, especially for patients with biphasic illness followed by severe disease symptoms. Refer to Leptospirosis Fact Sheet for Clinicians for more details about testing and treatment.
- Early identification of disease can facilitate prompt treatment and public health action. Encourage prevention methods to at-risk patients, including avoiding flood or freshwater, addressing rodent problems in the home or nearby areas, covering wounds with waterproof bandages, wearing gloves, boots or closed toe shoes during high-risk activities, and considering leptospirosis vaccination for pet dogs.
- Chicago clinicians who suspect (or have confirmed) a case of leptospirosis should call CDPH via the disease reporting line: 312-743-9000, option number 7.
The full warning from the Chicago Department of Public Health can be found below.
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