(Updates with more rain, storm, locust swarm)

By Bappa Majumdar

KOLKATA, India, July 5 (Reuters) - Health officials in India's flood-hit city of Kolkata said on Thursday they were worried about the outbreak of disease, as residents drank and swam in filthy, neck-deep water.

The city of over 8 million faced the prospect of more flooding as a storm, 50 km (20 miles) north of Kolkata, brought fresh downpours and uprooted trees. Weather officials forecast heavy rains over the next two days.

Monsoon rains have already swamped homes and disrupted power in the eastern city. Most schools were closed for the third day running and many offices empty as people avoided going to work through the flooded streets.

Authorities used sandbags to shore up embankments along the Hooghly river.

Health workers in boats distributed rehydration packets and medicine as reports of skin infections and fever came in.

"Each time I wade across the flooded streets, my skin starts burning," Ravindra Shaw, 33, a resident said.

As overflowing sewage mixed with rain water, health experts worried about the outbreak of disease.

"We are warning children not to swim in these waters and avoid wading across the streets just for fun as this could be hazardous," said Deb Dwaipayan Chattopadhyay, a senior health department official.

Many people also do not have clean drinking water.

"With safe drinking water reserves gone, people have no choice but to opt for contaminated water to survive," said Deepika Sur, a top official at the National Institute of Cholera and Enteric Diseases.

RIVERS SURGE

Storms, heavy rains and flooding have hit huge swathes of South Asia over the past 13 days, leaving close to 700 dead and scores missing as well as tens of thousands homeless.

In neighbouring Pakistan's desert-like Baluchistan province, tens of thousands of people remained homeless after a cyclone caused flash floods last week, leaving at least 132 people dead.

Around Kolkata, the Hooghly river and the nearby Matla -- swollen by monsoon rains -- were lapping at mud embankments and authorities asked residents to help reinforce defences with hundreds of sandbags.

For many inhabitants, the flooding brought back memories of week-long rains in 1978 that marooned tens of thousands in the teeming city for days.

The forecast of more rain from the storm has worried weary residents.

"We thought the rains would eventually stop but now, it seems, our troubles will continue," said Kuntal Mondol, a resident on the city's northern fringe.

In the western state of Gujarat, where over 40 people have been killed this week in monsoon flooding, authorities issued food packets and blankets to thousands of people.

The state also faced a threat from desert locusts after a U.N. warning that swarms of the grasshoppers could cross the Indian Ocean from the Horn of Africa.

The government has sent teams armed with pesticides and specialist equipment to Gujarat, where heavy monsoon rainfall will create favourable breeding conditions for the insects.

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