A cluster of illnesses in Oklahoma could have been caused by swimming in water contaminated with urine from rats, an expert suggests.
Several people have fallen ill after taking a dip in rivers and lakes near Bartlesville city, in the east of the state, officials say.
They are believed to be suffering from meningitis, or an inflammation of the lining of the brain or spinal cord caused by an infection.
Testing has already ruled out the brain-eating amoeba naegleria fowleri, which can lurk in stagnant water, but infectious disease expert Dr Thomas Russo said the cases may instead have been caused by a bacteria found in animal urine.
Health officials are urging people living in the area not to swim in rivers and lakes in the area before Memorial Day this weekend, the unofficial start of summer.
People who have caught the disease in Oklahoma include Keegan Smith (pictured) who became ill after swimming in Copan Lake
The above map shows Bartlesville, Oklahoma, and the two locations where local reports suggest cases have occurred
Among those affected is youngster Keegan Smith, who got sick after swimming in Copan Lake near Bartlesville.
His grandmother Terri Smith told FOX News 23: ‘He was having a terrible headache, running a fever, and had a kind of purple rash on his chest.
‘It weren’t just a normal headache for a little kid, it was a bad headache.’
She said he was being treated for suspected meningitis by doctors.
Testing showed he did not have Primary Amebic Meningoencephalitis, or PAM, which is caused by N. fowleri.
Another boy is also believed to have fallen ill with meningitis after swimming in the Caney River, which runs from Copan Lake through Bartlesville.
Dr Russo, from the University of Buffalo in New York, suggested to LiveScience that it was most likely the boys had been infected by a bacteria from the urine of animals — including rats, cattle and pigs.
Leptospira can lurk in these animals and then be excreted in their urine.
This can flow into waterways, or be washed into them by heavy rains, where the bacteria can remain for weeks.
When humans swim in contaminated water, swallow it or go into the water with an open cut or graze they can then become infected.
The infection — medically termed leptospirosis — emerges within a few days to a few weeks later.
Symptoms begin with fever, headache and muscle pain, but can then progress to jaundice, trouble breathing and meningitis.
There are up to 150 cases of infection with the bacteria in the US every year. But the disease is rarely fatal, with about one in 50 patients dying from the illness.
Dr Russo also suggested other explanations for the infections including enteroviruses — normally behind stomach problems — lurking in freshwater that were then ingested or Listeria, a cause of food poisoning that can also hide in water.
‘If the water was contaminated with an enterovirus and was ingested, it could potentially cause a meningitis syndrome,’ Dr Russo said.
The state health department also says there is a drought in the area at present, which can cause pollutants in water to become more concentrated.
Several people have fallen ill after taking dips in rivers and lakes near Bartlesville, in the east of the state. The two sites where illnesses have been reported at Copan Lake and Caney River (pictured above)
They are urging people to avoid swimming in rivers and lakes ahead of Memorial Day celebrations this weekend.
They said in a statement: ‘The [Health Department] is investigating a cluster of illnesses in the Bartlesville area.
‘What we know at this time is a few individuals have presented to healthcare providers with varying symptoms.
‘Initial testing has been negative for primary amebic meningoencephalitis, or PAM, caused by the organism Naegleria fowleri.’
They added: ‘We are continuing to monitor for more individuals who may be sick as a part of this cluster.
‘While investigations continue, if individuals feel ill, we encourage them to reach out to their healthcare provider and discuss their symptoms.’