In some regions, most camels carry a strain of the MERS virus in their blood. (AP photo/Health Protection Agency)

(Bloomberg) — An American who had contact with an Indiana health-care worker infected with a potentially lethal Middle Eastern respiratory syndrome (MERS) virus was found to have the disease, though he had no symptoms and didn’t require medical care.

The latest MERS-CoV coronavirus case, located in Illinois, is the third confirmed on U.S. soil, the Centers for Disease Control and Prevention (CDC) said in a statement.

The original U.S. case of MERS involved a person who returned April 24 from Saudi Arabia. That patient was successfully treated in a U.S. hospital and has since been released.

The newest patient, whom the CDC didn’t identify, “did not seek or require medical care,” the agency said.

Local health officials in Illinois have been monitoring the new patient’s health daily since May 3 as part of the CDC’s review of the outbreak, the agency said. The man met with the Indiana patient twice since he returned from Saudi Arabia.

The Illinois patient was first tested for MERS on May 5 and results were negative. A subsequent test turned up positive for MERS antibodies on May 16, though the man never reported feeling sick and is still “feeling well,” the CDC said.

Earlier, a 44- year-old man in Orlando, Fla., who arrived from Saudi Arabia on May 1 was diagnosed with MERS. He was admitted to Orlando’s Dr. P. Phillips hospital on May 8.

He was “in good condition and continuing to improve,” the hospital said May 12.

A spokesman for the hospital, Geo Morales, didn’t immediately respond to an e-mail today asking for an update on the Orlando patient’s current condition, or the results of tests on hospital workers. At least 20 workers at Philips were tested for MERS and one was admitted to the hospital, although the person wasn’t found to carry the virus.

The MERS virus belongs to the same family of pathogens as SARS, which killed about 800 people worldwide after first appearing in China about a decade ago.

Symptoms of MERS include coughing, fever and respiratory distress. None of the U.S. MERS patients appear to have developed life-threatening illness.

MERS has sickened at least 614 people, killing 184 of them since 2012, according to the World Health Organization (WHO).

But the WHO’s emergency committee last week decided against declaring MERS a global health emergency, citing the lack of evidence for sustained human-to-human transmission. Most of the infections have been because of poor infection-control practices in hospitals, the WHO said.

Saudi Arabia expects millions of Muslims from around the world to perform the annual Hajj pilgrimage to Mecca and Medina in early October. The WHO doesn’t recommend any travel restrictions related to MERS, though Saudi Arabia has suggested that pilgrims over 65 years or under 12, and pregnant women, refrain from the journey.

The CDC appears to share WHO’s skepticism about the magnitude of the threat posed by MERS.

“This latest development does not change CDC’s current recommendations to prevent the spread of MERS,” said David Swerdlow, who is leading CDC’s MERS response, in the agency’s statement. “It’s possible that as the investigation continues, others may also test positive for MERS-CoV infection but not get sick.”

Origins

While most of the cases and deaths have been in Saudi Arabia, there have been infections in Europe, Africa, Asia and the U.S. All cases are linked to people who live in or have traveled to the Middle East, or who were exposed to someone who traveled to the Middle East.

The potential route of transmission from camels to humans isn’t well understood. Many cases of the illness have occurred among camel herders and people who visited camel farms or consumed unpasteurized camel milk.

This month, researchers in the Netherlands have reported in a new study in Emerging Infections Diseases – a CDC journal — that the MERS coronavirus occurs frequently in camels in Nigeria, Tunisia and Ethiopia, not just in camels in Saudi Arabia.

The researchers based their study on an analysis of camel blood samples collected from 2009 through 2011. The first human cases of MERS came to world health officials’ attention in 2012.

The Dutch researchers say they found MERS in almost all of the blood samples taken from 358 dromedary camels in Nigeria and 188 camels in Ethiopia.

In Tunisia, MERS was found in 54 percent of adult camels, and in all of the animals from one southern province.

The findings add to previous studies that have found the virus in camels in Spain’s Canary Islands and in Egypt, as well as in several nations on the Arabian peninsula.

The findings also suggest that there may be undiagnosed human cases in Africa, the Dutch researchers wrote.

“The possibility exists that [human] MERS-CoV illness occurred before its discovery in 2012 and that such infection has been overlooked in the areas with evidence for virus circulation among animals during the past 10 years,” the authors wrote in the journal.

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