Officials warn of deadly brain-swelling bacteria lurking in the water of spring break hotspot
Health officials are warning of a deadly bacteria lurking in Hawaii’s flood waters.
The Hawaii Department of Health (DOH) and Hawaiian Humane Society (HHS) have urged residents and recovery workers to monitor for signs of leptospirosis after the ‘Kona low’ storms that hit earlier this month.
The storms dumped more than two trillion gallons of rain across the state, enough to fill three million Olympic-sized swimming pools. Throughout March, some areas recorded 14-day rainfall totals 3,000 times higher than normal, and wind gusts reached up to 135mph.
In addition to causing devastating damage, the storm waters also left behind the dangerous bacteria. Leptospirosis is a rare but potentially deadly illness caused by the bacterium Leptospira, which contaminates water and soil.
Leptospira bacteria spread through the urine of infected animals and survives in water or soil for weeks or months at a time. During heavy flooding, rainfall or hurricanes, contaminated soil or water can get into the body through the nose, mouth, eyes or break in the skin.
Once the bacterium infiltrates the body, it can travel to the bloodstream and attack vital organs, leading to trouble breathing, coughing up blood, black or tarry stool and blood in the urine.
Left untreated, severe leptospirosis can cause liver, kidney and respiratory failure, as well as brain swelling. It may also cause severe pulmonary hemorrhagic syndrome (SPHS), massive bleeding into the lungs.
While it’s rare for leptospirosis to spread from person to person, living in temporary shelters, such as during a storm, or facilities with a rodent infestation could increase the risk.
Pictured above are US National Guard soldiers assisting flood recover efforts in Waialua, Hawaii, on March 21, 2026 (file photo)
Leptospira bacteria, which causes leptospirosis, is pictured in the above illustration (stock image)
Up to one in six patients with severe leptospirosis die, but among those with SPHS, the mortality rate can reach 50 percent.
‘Hawaii already has among the highest rates of leptospirosis in the country due to its warm, wet climate,’ HHS and DOH said, ‘and flooding events like the recent Kona low storm can dramatically increase exposure risk by spreading contaminated soil and water across a broad area.’
About 100 to 200 cases of human leptospirosis are reported in the US each year, half of which occur in Hawaii due to the state’s heavy rainfall and frequent flooding. Puerto Rico, California and Illinois also report sporadic cases.
The disease primarily affects those with recreational exposure to soil and water, such as veterinarians and farmers, or those participating in recreational water sports like swimming and kayaking.
Leptospirosis in humans has two phases: leptospiremic (acute) phase and immune (delayed) phase.
People in the leptospiremic phase may have mild flu-like symptoms or none at all, but as the bacteria moves through the bloodstream, more severe signs like vomiting, fever and diarrhea can occur.
These signs usually start within two to 14 days after infection and last three to 10 days.
In the immune phase, bacteria moves from the blood to the organs. In rare cases, this phase can cause Weil’s syndrome, leading to internal bleeding and organ failure.
In pets, leptospirosis causes fever, decreased appetite or lethargy, vomiting, diarrhea, increased thirst or urination, muscle soreness, reluctance to move or jaundice.
Pictured above is an aerial view of flooding in a residential neighborhood in Waialua, Hawaii, on, March 20, 2026 (file photo)
Haleiwa, Hawaii, residents Kaybri Jones, left, and Anthony Scala are seen removing debris after flooding (file photo)
‘After heavy rain and flooding, we typically see an elevated risk of leptospirosis in our community, and this storm is no exception,’ Dr Lisa Labrecque, Chief Veterinarian at the Hawaiian Humane Society, told the Honolulu Star-Advertiser.
‘So many families were doing everything they could just to get through this storm, and their pets were right there with them in those conditions.
‘If your pet begins showing any signs of illness in the coming days, please reach out to your veterinarian immediately. Early treatment with antibiotics is effective, but this disease can progress quickly and become life-threatening, if left untreated.’
Leptospirosis can be treated in both pets and humans with antibiotics. There are no vaccines available for humans, though there is a two-dose shot for dogs.
‘Pets are often the first indicator that leptospirosis is circulating in a community, and after a flooding event like this one, that risk is very real,’ Dr Ariella Barry, Epidemiology and Laboratory Capacity Veterinary Medical Officer with the DOH Disease Investigation Branch, told the Honolulu Star-Advertiser.
