Health officials have backtracked on an earlier report that a mysterious Middle East virus had apparently spread from one person to another in the US.
Additional testing has shown the virus did not, in fact, spread to an Illinois man from a traveller he met in a business meeting.
This month, a doctor who travelled from Saudi Arabia to Indiana was identified as the first US case of Middle East respiratory syndrome (Mers). Officials tested people he met, and two checks detected antibodies against Mers in the Illinois man. No other contacts tested positive.
On May 17, officials at the Centres for Disease Control and Prevention (CDC) said the Illinois man was not sick and tests for presence of the actual virus in him had been negative. But the blood tests that detected antibodies to the virus were sufficient grounds to take action.
Health officials began testing people he had been in contact with and asked the man to wear a mask and avoid crowds.
Since then, other tests - including a more definitive one that takes five days to complete - have discounted that finding, CDC officials said on Wednesday.
But one official said the CDC would continue to err on the side of caution if it might stop the spread of the disease. "We can't wait until we have all the tests back to take public health action," said Dr David Swerdlow.
Mers has infected more than 600 people mostly, in the Middle East, and killed more than 175. It belongs to the coronavirus family that includes severe acute respiratory syndrome (Sars), which killed 774 people in 2003, including 299 people in Hong Kong.