Editor's note: This story was updated on May 28.
May 27, 2014 -- All hospital workers in Florida and Indiana who were in contact with the patients diagnosed with Middle East respiratory syndrome (MERS) have been cleared to return to work, hospital officials say.
In Florida, follow-up testing on all 23 health care workers exposed to the MERS patient showed they didn't catch the virus, according to Dain Weister, a spokesman for the Florida Department of Health. They were able to return to work May 24.
In Indiana, all 50 employees of Community Hospital in Munster who had direct contact with the patient diagnosed there did not catch MERS either, a second test confirmed, according to the hospital.
MERS first surfaced in Saudi Arabia in 2012. As of May 28, 636 confirmed cases have been reported, according to the World Health Organization, with 193 deaths. The death rate of MERS is about 30%.
The virus first appeared in the U.S. May 2, when a health care worker traveled from Saudi Arabia to Indiana, then went to the emergency room in Munster with symptoms. Fever, cough, and shortness of breath are typical MERS symptoms.
A second health care worker who traveled from Saudi Arabia to Orlando fell ill upon his arrival in Florida, with health care officials confirming that case May 11.
Both patients have been discharged from the hospital.
A third man from Illinois, who had met with the Indiana MERS patient twice before the patient was hospitalized, was initially thought to have been exposed to the virus. At the time, his blood test showed potential exposure to MERS in the past. But CDC officials now say that in-depth testing showed the Illinois man was not infected.
The MERS virus is also known as MERS-CoV, or coronavirus. Coronaviruses are a large family of viruses. They cause a range of illnesses in people and animals. The source of MERS is not known, according to the CDC, although the virus has been found in camels and a bat. There is no vaccine.
The CDC does not recommend any change in travel plans. It advises travelers to take precautions: Wash hands with soap and water often, and avoid sick people.
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