NBC News - A second case of the mysterious MERS virus has been found in Florida, federal health officials announced Monday.

Officials were preparing to release more details about the case later on Monday.

The first known U.S. patient with Middle East Respiratory Syndrome — a healthcare worker in his 60s — went home on Friday from the hospital in Munster, Indiana, where he had been treated. Doctors said he recovered fully.

The patient was kept isolated while he was treated for the virus and health workers who cared for him before they knew he had MERS were kept quarantined and tested for the virus. So far, he does not seem to have infected anyone else and the normal incubation period has passed.

Close to 500 cases of MERS have been reported to the World Health Organization. WHO says the virus is on the upswing, but most cases are in Saudi Arabia. WHO says for some reason hospitals in Saudi Arabia are not able to control the spread of the virus.

It’s been traced to camels and Saudi officials have cautioned people to take care when handling camels, their meat or milk. But no one is sure yet how people are being infected, and most people who have been diagnosed have not had direct contact with camels.

Experts say careful infection control can keep the virus from spreading.

Many hospitals around the world have been phasing in such precautions as the world keeps an eye out for new pandemics, and as evidence piles up on how to stop all sorts of infections, from drug-resistant superbugs such as MRSA to avian influenza.

There's no vaccine and no specific treatment for MERS, which was only identified in 2012. It’s caused by a coronavirus, in the same family of viruses that cause common cold symptoms, but also a relative of the severe acute respiratory syndrome (SARS) virus that swept the world in 2003.

SARS sickened around 8,000 people and killed about 10 percent of victims before it was stopped.

WHO officials fear MERS could do the same thing. So far it has had about a 30 percent fatality rate, but it's less infectious than SARS was.