India's flood-ravaged Kerala state is facing shortages of a drug that fights an infectious bacterial disease after the worst flooding in a century, forcing authorities to turn to other states to help ramp up supplies.

Suspected cases of leptospirosis, a waterborne disease known locally as "rat fever," has climbed to 800 since mid-August, a health ministry spokesman said. Transmitted via the urine of infected animals, its symptoms include muscle pain and fever.

Confirmed deaths caused by leptospirosis so far total 12, while suspected deaths, pending full medical reports, number 41, the spokesman added.