Kerala, the southern Indian state reeling from its worst flooding in a century, is now battling a “fast, progressive” strain of leptospirosis, or “rat fever”, as it is known locally.

Some 200 cases of the infection have been confirmed so far, a health ministry spokesman said, and authorities suspect it is the cause of dozens of deaths since mid-August.

The waterborne bacterial disease can prove fatal and is transmitted by the urine of infected animals, with symptoms including muscle pain and fever.

The outbreak comes after flooding triggered by torrential rain devastated almost the entire state, destroying thousands of homes, killing hundreds of people and running up a bill for at least £2.81bn in damage.

The health ministry began distributing preventative medicine last month and warned about the outbreak of leptospirosis and other waterborne diseases such as typhoid and cholera, health minister K K Shailaja told reporters.

Local media reported three leptospirosis deaths on Monday.

“The victims had unfortunately not taken preventive medicine,” the minister said.

Overall, nine deaths from the disease have been confirmed, but the number may rise to over 40 pending full medical reports, the ministry spokesman said.

Leptospirosis rarely spreads from person to person and can be treated with common antibiotics.

“In the past week, we have seen about 30 deaths in Kozhikode and Wayanad,” said Mohammed Javeed, internal medicine specialist at a private hospital in Kerala, referring to two of the worst flood-affected districts on the state’s southwest coast.

Mr Javeed said the state has leptospirosis cases every monsoon season as paddy fields fill with water, increasing the chance of infection for farmers, especially through wounds such as cuts.

Volunteers rescue animals in kerala floods

Of particular concern, however, is that some of the victims this year did not have usual symptoms such as mild jaundice, blood in urine or bleeding spots on the skin, he said.

“This time it is a fast, progressive infection,” Mr Javeed. “The recent deaths indicate clearly the threat of an epidemic.”

Medical professionals are continuing to dispense preventive medicine in the form of tablets which need to be taken once a week for a month, he added.

According to the World Health Organisation, leptospirosis' incubation period is between five and 14 days. Symptoms can be as mild as a flu-like illness but it can be fatal.

The infection can be transmitted to humans through cuts and abrasions, or through the mucus membranes of the eyes, nose or mouth, the body said.

Kerala floods: heavy monsoon rains lead to deaths in India Show all 40 1 /40 Kerala floods: heavy monsoon rains lead to deaths in India Kerala floods: heavy monsoon rains lead to deaths in India A man removes debris from a collapsed house after floods in Paravur Reuters Kerala floods: heavy monsoon rains lead to deaths in India An ariel shot of Kerala from Thiruvanpuram Getty Kerala floods: heavy monsoon rains lead to deaths in India Murgan and his family clean up their house in Mundancavu village at Chegannur upon returning home after the flood waters receded Getty Kerala floods: heavy monsoon rains lead to deaths in India People assess damage caused by floods on the outskirts of Kochi AP Kerala floods: heavy monsoon rains lead to deaths in India Men paddle their boat through the lawns of a partially submerged church at Kuttanad in Alleppey district Reuters Kerala floods: heavy monsoon rains lead to deaths in India Sandhya Biji and her son in front of their damaged house on the banks of Pamba river Getty Kerala floods: heavy monsoon rains lead to deaths in India Border Security Force distribute food food and water to the residents who are stuck in their houses as well who have not vacated houses because of the flood water in interior places at Allapy Getty Kerala floods: heavy monsoon rains lead to deaths in India A damaged house on the banks of Pamba river Getty Kerala floods: heavy monsoon rains lead to deaths in India Murgan cleaning up his house Getty Images Kerala floods: heavy monsoon rains lead to deaths in India An aerial view shows partially submerged houses at a flooded area in the southern state of Kerala Reuters Kerala floods: heavy monsoon rains lead to deaths in India Murgan and his family clean up their house Getty Images Kerala floods: heavy monsoon rains lead to deaths in India People are airlifted by the Indian Navy soldiers during a rescue operation Reuters Kerala floods: heavy monsoon rains lead to deaths in India People wait for aid on the roof of their house Reuters Kerala floods: heavy monsoon rains lead to deaths in India Indian volunteers and rescue personal evacuate local residents AFP/Getty Kerala floods: heavy monsoon rains lead to deaths in India Indian people use a boat to rescue an elderly man in the flooded water in Kochi EPA Kerala floods: heavy monsoon rains lead to deaths in India An aerial view shows partially submerged houses at a flooded area in the southern state of Kerala Reuters Kerala floods: heavy monsoon rains lead to deaths in India An Indian woman watches residents walking through flood streets next to their marooned houses AFP/Getty Kerala floods: heavy monsoon rains lead to deaths in India Indian army personal evacuate local residents AFP/Getty Kerala floods: heavy monsoon rains lead to deaths in India Indian commuters wade through flooded streets AFP/Getty Kerala floods: heavy monsoon rains lead to deaths in India People move past a flooded road in Thrissur AP Kerala floods: heavy monsoon rains lead to deaths in India Water gushes out following heavy rain and landslide in Kozhikode AP Kerala floods: heavy monsoon rains lead to deaths in India Fire and Rescue personnel evacuate local residents in an inflatable boat from a flooded area at Muppathadam near Eloor AFP/Getty Kerala floods: heavy monsoon rains lead to deaths in India Indian residents look at the Shiva Temple submerged AFP/Getty Kerala floods: heavy monsoon rains lead to deaths in India Roads and houses engulfed in water following heavy rain and landslide in Kozhikode. AP Kerala floods: heavy monsoon rains lead to deaths in India People look at vehicles stuck in the mud AFP/Getty Kerala floods: heavy monsoon rains lead to deaths in India A young man wades through a flooded street in Kochi EPA Kerala floods: heavy monsoon rains lead to deaths in India Rescue operations being conducted at the landslide location at Kuttampuzha AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India An elderly woman is rescued in a cooking utensil AP Kerala floods: heavy monsoon rains lead to deaths in India Local residents look at a partially destroyed house after heavy monsoon rains led to a landslide in Kannappankund AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India An Indian woman sits inside her house immersed in flood waters in Ernakulam district of Kochi AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India Indian fire and rescue personnel evacuate local resident AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India A woman stands at the door of her flooded home in Kochi EPA Kerala floods: heavy monsoon rains lead to deaths in India India residents stand on the shore as Periyar river flooded AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India An Indian man carries a basket of bananas next to houses immersed in flood waters AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India Laborers hailing from northern states wade through flood waters as they shift to higher ground AP Kerala floods: heavy monsoon rains lead to deaths in India Kerala chief minister Pinarayi Vijayan (L) along with opposition leader Ramesh Chennithala (2L) visit relief camp in Chengamanadu Government Higher Secondary School AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India Athirampally Falls EPA Kerala floods: heavy monsoon rains lead to deaths in India epa06939658 A structure is submerged in flood water following heavy rain in Kochi, Kerala state, India, 09 August 2018 (issued 10 August 2018). According to reports, the Indian state of Kerala has been hit by heavy rains, causing floods and killing at least 20 people. Indian Meteorological Department (IMD) has predicted heavy rain to continue on the 10 August. EPA/PRAKASH ELAMAKKARA PRAKASH ELAMAKKARA EPA Kerala floods: heavy monsoon rains lead to deaths in India Indian residents look at houses destroyed by flood waters at Kannappankundu AFP/Getty Images Kerala floods: heavy monsoon rains lead to deaths in India Kochi's International airport apron flooded AFP/Getty Images

Kerala residents returning to their homes have faced another threat, it emerged last month – deadly snakes and scorpions hiding in beds, cupboards and under carpets.

Authorities said thousands of arachnids and reptiles were likely to have been washed into houses that had been submerged.

During the floods more than one million people were evacuated from their homes. Officials said they believed more than 360 people were killed amid the national crisis.

Volunteer fishermen were hailed as “heroes” after they came inland from the coast with a fleet of about 600 boats to rescue villagers.