This year, the number of foreigners coming to India for medical care rose 30 per cent to 175,000, according to the Confederation of Indian Industry. It expects this number to rise to 200,000 next year - and to grow at similar rates for years to come.

Management consultants McKinsey & Company estimates that by 2012 the industry will be able to handle 1 million tourists a year, generating revenue of 50 billion rupees (HK$9.77 billion) to 100 billion rupees.

It is not just the numbers that are rising. Industry experts say that while a few years ago most medical tourists to India came for procedures such as cosmetic surgery and dentistry - practices not usually covered by medical insurance or government health schemes - today people are drawn to India for more complicated, serious operations.

'There's definitely been a change in recent times,' said Hari Boolchandini, marketing manager for Indraprastha Apollo Hospitals, India's biggest hospital provider.

'Before we used to get patients mainly for cosmetic work and non-complicated surgeries. But in the past two to three years we've started getting more serious cases. About 80 per cent of the patients flying in today are coming for procedures like cardiac surgery, orthopaedic joint replacements, spine and neuro surgery, and liver and kidney transplants.'

The reasons for patients looking for care outside their own countries remain the same as they have for years: high costs and inadequate insurance in countries such as the US, long waiting lists in countries with government-funded health care like Britain, and a lack of expertise, especially in some Asian, African or Middle Eastern countries.

Fortis Hospitals, India's second-largest health-care provider, says its target market is the 43.6 million Americans who do not have health insurance. Another big chunk of business comes from Britain, where some patients have to wait a long time for operations.

But the real driver for growth has come from within India itself. As its economy has flourished and the middle class has grown, demand has arisen for high-quality private health care. Modern, well-equipped private hospitals have followed.

'There is a surge in middle-class Indians who want the best and are prepared to pay for it; that's what's led to all this,' said Sanjay Sharma, head of sales and marketing at the Fortis hospital in Vasant Kunj, one of several hospitals Fortis runs in Delhi.

The hospitals that have been established to meet this demand may be costly by Indian standards, but compared with many other countries they offer excellent value.

'We are almost 20 times cheaper than the US and around 10 times cheaper than the UK for most high-end procedures,' said Mr Boolchandini, from Indraprastha Apollo Hospitals.

'A person could fly first class to Delhi, get his cardiac surgery done, take a tour of Agra and Jaipur and fly back first class again to the US - and he would still end up paying a quarter of what he would pay back home.'

In Ms Hersch's case, the discovery that India had cheap private hospitals was a godsend, she said. Without comprehensive medical insurance, her doctor told her she would have to wait two years for a hip replacement in California.

'I told him if I had to do that I'd shoot myself, I was in such agony,' Ms Hersch said.

'From now on, every time I need medical care, I'll just come here.'

But low costs alone are not enough to attract a steady stream of foreigners to India. The country also boasts well-qualified doctors and surgeons, many of whom have trained overseas.

'Our doctors are trained at some of the best hospitals across the globe and they keep themselves updated - theoretically and practically - by being in touch with the international medical community,' Mr Boolchandini said.

He said another bonus was that many Indians spoke English.

'So communication is not a problem,' he said. 'And visitors can get any kind of food they want, at least in the bigger cities where we have hospitals.'

Many hospitals popular with patients from overseas try to offer an experience that is as close to a holiday as possible. At the Fortis hospital in Vasant Kunj, a vast building that proclaims its cleanliness in a typically dusty Delhi street with a spotless white-tiled facade, a doorman with a huge moustache and wearing a white turban helps patients out of their taxi with a flourish.

Inside, patients have a choice of rooms, the grandest of which, the Presidential Suite, is decorated like an especially swanky five-star hotel room, with oil paintings, a huge flat-screen TV and leather sofas. But at 35,000 rupees a night it is cheaper than five-stars in Europe and includes nursing care and food.

Hospitals say most foreign patients come and go - picked up from and delivered to the airport by hospital staff - without holidaying. But a number of hospitals have entered into joint ventures with high-end resorts, where nurses care for post-operative patients.

Fertility treatment for overseas patients is also likely to become a growing field. Pramod Sharma, at the Pratiksha Hospitals in Guwahati, Assam, for example, specialises in IVF and surrogacy for foreigners.

Foreign health-care firms have not yet established hospitals, but it is only a matter of time.

Earlier this month, Tourism Minister Ambika Soni said India was trying to simplify procedures for foreigners to invest in Indian hospitals and hotels. She expected US$6.5 billion to flow into the sector in the coming years.

Dr Sharma, of Fortis, said the greatest potential for growth came from overseas insurance companies. If insurance packages included options of Indian care, premiums would be drastically lowered, he said, pushing up the number of Americans with insurance.

In India, meanwhile, only a fraction of the population has health insurance. Most people are dependent on government-funded hospitals. These will find it harder and harder to recruit doctors as the number of private hospitals offering high salaries grows.

For poor Indians who cannot afford private medical care, this is a very different story. Compared with the US - from where so many of India's medical tourists hail - India has 20 per cent of the number of hospital beds per capita and a quarter the number of doctors. The government's per-person spending is 1.5 per cent that of the US.