Heavy floods in southern India have damaged hundreds of millions of dollars worth of crops and could lead to severe food shortages, aid agencies say.
More than 250 people have died and millions have been displaced in the states of Andhra Pradesh and Karnataka after the worst floods in decades.
Authorities in Karnataka have warned against the outbreak of water-borne diseases in camps for flood victims.
The rains came on the back of one of the worst droughts in India.
Relief workers are trying to transport food and medicines to hundreds of thousands of people who remain cut off in their villages by flood waters.
"There could be 200,000 to 300,000 people in villages where aid has not reached," HV Parashwanath, secretary of Karnataka's disaster monitoring agency told the AFP news agency.
More than a million people are now living in temporary relief camps.
Aid workers are also supplementing the government's efforts.
Cases of villagers suffering from viral fever, diarrhoea and chikungunya, a form of malaria, have been reported from a few flood-affected districts of Karnataka, officials say.
"We have asked everybody to be alert and careful," Karnataka health secretary IR Perumal told BBC.
Teams of doctors have spread out across affected districts, and water-purifying tablets are being distributed, officials say.
"There is a danger of epidemic diseases," Red Cross official NG Narayana said.
But concern is now growing over the long-term impact of the floods.
Only last week the government announced that India had experienced its worst drought in nearly 40 years.
The floods have now dashed any hopes of a recovery in food production, according to World Vision.
"At a national level this will definitely have a say on our food stocks because these places in south India were the ones where there was some evidence of monsoon and summer crop having survived. But now that also is gone at least in Andhra, Karnataka and these districts," Jayakumar Christian, India director for World Vision said.
"Earlier there was migration due to drought and now there is migration due to monsoon," he said.
India's defence ministry said the army had delivered more than 4.5 tonnes of food to survivors who had lost their food stocks.
The rains were blamed by weather experts on a cyclone in the Bay of Bengal.