By Zeba Siddiqui

MUMBAI (Reuters) - Campaigners and a former official overseeing Asia's largest tuberculosis hospital in Mumbai say staff deaths there are being under-reported, highlighting India's growing struggle to contain multi-drug resistant forms of the contagious, airborne disease.

Many of India's toughest TB cases end up in the metal cots of the state-run Sewri Hospital, where on a recent Reuters visit open wards were lined with emaciated patients, many left alone by families scared by the disease and its stigma.

Medical Superintendent Rajendra Nanavare, Sewri's top doctor, says an average of six patients a day die at the 1,200-bed hospital.

Nanavare says a dozen hospital workers had also died from TB in the last five years. But others say the real number of staff deaths is higher - although they could not give a precise figure - pointing to a public health crisis at the heart of one of the world's most densely populated cities.

"A lot of class 4 workers like the sweepers and the cleaners at the hospital leave work after they get the infection," said Prakash Devdas, president of the local workers' union.

"We don't know if they're alive with the infection or dead. Nobody tracks them. That's why I said the actual number would be much higher."

Campaigners blame weak infection controls, poor oversight and infrequent checks on workers in a country where the shame of TB alone drives people to suicide.

"There is so much interaction between the patients and staff. They become more vulnerable... especially if they have weak immunity," said former TB officer Mini Khetarpal, who supervised the hospital for Mumbai authorities until earlier this year.

Nanavare said 69 employees has been diagnosed with TB since 2011, of whom 12 had died while 28 had been cured.

A lot of staff continue to work at the hospital long after being infected.

GLOBAL HEALTH THREAT

India has the world's largest number of TB patients - an estimated 2.6 million Indians live with the bacterial lung disease, which is spread through coughs and sneezes.

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The country is second only to China in the number of patients with drug-resistant TB, a major threat to TB control with repercussions well beyond India.

In July this year, a Mumbai woman who flew to Chicago was found to have the extremely drug resistant TB (XDR TB). She has since been quarantined and is under treatment there.

"Globally, XDR TB presents the greatest threat to TB control," said Brian Katzowitz, a spokesman at the Centers for Disease Control and Prevention, the leading national public health institute in the United States.

Nerges Mistry, director of the Mumbai-based Foundation for Medical Research, investigated conditions at the Sewri hospital at the behest of city authorities in 2011. That report - seen by Reuters but not released publicly - found about 65 hospital staff died between 2007 and 2011, many of them cooks.

It also highlighted serious problems including inadequate record-keeping, sanitation and hygiene problems. Doctors failed to wear N-95 disposable masks, it said, a basic form of infection control recommended by the World Health Organization.

Mistry said it was unclear if any of the proposals made were implemented.

"It's a last ditch thing. You go there and you never come out," she said.

Nanavare says the hospital has brought in changes to ensure better staff protection, though masks remain an "individual decision".

HIGH PRIORITY

Prime Minister Narendra Modi's manifesto ahead of last year's election accorded "high priority" to the health sector, and promised a universal health assurance plan.

But he has been forced to tightly control healthcare spending as India battles to spend its way out of slow-moving recovery.

In the latest high profile case at the Sewri hospital, a nurse died in September from drug-resistant TB, prompting staff protests to demand better working conditions.

High profile campaigners such Leena Menghaney, an HIV and TB activist, say still not enough is being done.

"Despite increased investment in prevention and treatment of drug resistant TB over the last decade, local authorities, the National TB Programme and policymakers in India are not directing sufficient attention to infection control," she said.

Mumbai city officials in charge of overseeing the hospital say sub-standard private care before patients are sent to Sewri must share the blame for its travails.

A Reuters reporter found cats wandering around wards and few visible instructions to keep visiting relatives safe. None of the nurses wore masks and two said they were encouraged not to, on the grounds that they were already exposed to TB bacteria.

One patient, 12-year-old Kamala, wore a light green muslin mask, untied at one end. "I just removed it because I was coughing too much," she said.

A group of about 60 health experts and activists including the U.S.-based Treatment Action Group, wrote a letter in August to the state, federal and city authorities highlighting what they described as "dismal" conditions at the hospital.

They have yet to receive a response.

Sunil Khaparde, a health ministry official in New Delhi who oversees India's TB control program, said the hospital had been asked to tighten procedures and more training was planned.

"The Sewri Hospital is in urgent need for a facelift," said Zarir Udwadia, a chest physician at Hinduja Hospital in Mumbai and one of India's best-known TB experts. "More funds, more staff and more commitment are needed."

(Additional reporting by Aditya Kalra in New Delhi; Editing by Clara Ferreira Marques and Alex Richardson)