According to Dr Vinay Agarwal, secretary of the Indian Medical Association, direct heat can cause sun stroke. And this is the best time of the year for viruses.

But summer is not only the time for viral infections but also bacterial infections -- which can spread through water and food -- and the result may be gastroenteritis, cholera, typhoid and jaundice.

Long exposures out of the shade can make the body temperature shoot up to 106 or 107 degrees Celsius, causing brain fever and cardiac arrest. The remedy, say the doctors of the Respiratory and Critical Care Group of Apollo Hospital, is to consume plenty of oral fluids besides staying in the shade as much as possible.

A person suffering from heat stroke will start getting drowsy, confused, he might have headaches, episodes of vomiting, dizziness and abdominal pain. In Delhi around 12 people die of heat strokes every year, the number is around 4,000 in the whole of the United States, say Dr Rajesh Chawla, Dr Avdhesh Bansal, Dr M.S. Kanwar and Dr R.K. Manit of the critical care group.

Heat stroke can be caused by exertion as among athletes who can prevent it by running early in the mornings, taking fluids during the race and avoiding alcohol or beer during the race. Heat stroke is a medical emergency and the treatment should be quick, they said. The patient should immediately be taken to the hospital. He or she should be given a vigorous massage, plenty of fluids and ice packs can be pressed on the flanks, they said.

While fluids can prevent sun strokes, they can also be carriers of other diseases if infected with germs causing gastroentritis, cholera, typhoid and jaundice, Dr Vinay Agarwal of the IMA said.

Water from shallow handpumps and ice made from such water could be infected. Other remedies for heat like cut fruits, sugar cane juice, `bunta' sodas and ice `golas' can all lead to disease, he said.

`Bunta' sodas are strictly to be avoided, he says, as the water used is always contaminated, the ice used in sugar-cane juice is just as bad. Besides both cane machines and cut fruits attract flies which are a sure way to get cholera.

Of the options then available apart from boiled water in bottles brought from home, are aerated drinks like Coke and Pepsi and bottled mineral water.

According to IMA, the government should ban the sale of cut fruit and also close ice factories which don't conform to standards of cleanliness, Agarwal said. While gastroenteritis presents itself as a case of food poisoning, beginning with vomiting and affects one person at a time, while diseases like cholera could turn out to be an epidemic.

Doctors say that the best way to treat cholera is the oral rehydration solution. Besides lemon which has bactericidal properties can be had with a pinch of salt and some sugar all through summer to prevent infections.