Rotting carcasses of livestock contaminating water in the aftermath of devastating floods in India's Kerala state have given way to a new challenge - battling infectious disease such as leptospirosis or "rat fever".At least 34 deaths in the state since August are suspected to be from leptospirosis. Deepu, an official at the ministry of health in Kerala's capital Trivandrum, told Al Jazeera 515 cases were reported in the past 17 days, 196 of those confirmed.Doctors say rat fever symptoms include high fever, severe muscle and abdominal pain, nausea and vomiting."This is a direct consequence of the flood. The host of this disease is the rat, hence the name rat fever," said Rajeev Sadanandan, chief secretary at Kerala's health department."But there are secondary hosts like cattle and dogs. Once they get infected, their urine carries the bacteria. Since a lot of these infected animals died during the floods, the bacterial levels in the water is high."The disaster - the worst floods the tourist haven of Kerala has witnessed in a century - killed nearly 500 people, drove one million out of their homes, knocked buildings down, washed away farmland, and destroyed major roads and bridges.Infection in the fieldsAmong the latest disease victims was Ujesh, 38, a part-time farmer who died on Saturday in Vadakara, which is among the worst-hit regions. "He was suffering from high fever and severe headaches. He probably caught the infection in the fields. He was working even when the heavy rains hit," Ujesh's brother-in-law Suresh, told Al Jazeera.The outbreak of disease following the devastating floods is causing concern, despite the government announcing it will seek to borrow more than 100bn Indian rupees ($1.4bn) to finance reconstruction work.At the state assembly on Thursday, Kerala Chief Minister Pinarayi Vijayan said the economic losses from the deluge would exceed $3.73bn. 'Severe calamity'The focus has now shifted to clean-up efforts and hospitals preparing to deal with possible outbreaks of water and air-borne disease as people return home from relief camps."We had anticipated this so Doxycycline, which is an antibiotic, was prescribed to people across flood relief camps as preventive care. But we now know that many people simply failed to take the medication," Dr V Jayashree told Al Jazeera from Kozhikode district.The state government has deployed special units of doctors and nurses to flood-affected areas, officials said.In New Delhi, India's central government classified the floods as a "calamity of severe nature" and committed $84.3m so far.