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CDC Confirms MERS Cases in U.S., Issues Travel Alert

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May 29, 2014

UPDATE: The CDC has determined that the third patient, the Illinois resident, does not have MERS. Earlier tests indicated antibodies to coronavirus, the family of virus to which MERS belongs. However, subsequent, more sophisticated tests completed after the CDC announced the third case of MERS indicate that earlier findings of MERS antibodies in the Illinois patient were antibodies to a much milder coronavirus. (There are six known coronaviruses, according to the CDC. Four cause very mild illness and two others cause MERS and severe acute respiratory syndrome (SARS), which can be lead to severe illness and death.)

"The initial ELISA and IFA serology results indicated the possibility that the Illinois resident had been previously infected with MERS-CoV," said David Swerdlow, MD, who is leading CDC's MERS-CoV response. Since then, however, CDC scientists have tested additional blood samples and completed a slower and more definitive serology test, called a neutralizing antibody test, which requires at least five days before a result is available. Based on the result of all of these tests, the CDC has concluded that the Illinois resident was not previously infected with MERS-CoV.

"While we never want to cause undue concern among those who have had contact with a MERS patient, it is our job to move quickly when there is a potential public health threat," said Dr. Swerdlow. "Because there is still much we don't know about this virus, we will continue to err on the side of caution when responding to and investigating cases of MERS in this country." So far, active MERS-CoV infection has not been found in any of the contacts of the two people in the U.S. definitively confirmed to have the disease.

Original article published May 28, 2014:

As of May 20, three cases of Middle Eastern Respiratory Syndrome (MERS), caused by a potentially fatal virus (MERS-CoV), have been reported in the United States by the Centers for Disease Control and Prevention (CDC).

Two of the patients diagnosed with the virus are healthcare workers who had traveled from Saudi Arabia, where many cases of the virus have been confirmed. Those two patients were hospitalized and have now been released and are healthy. A third person was confirmed by lab tests to have developed antibodies to the MERS virus, indicating exposure. However, he did not test positive for the virus and did not become ill. The individual had not been outside the U.S., but had contact twice with one of the returning healthcare workers.

While CDC director Thomas Frieden, MD announced after the first U.S. confirmation of a patient with MERS that the agency had been expecting cases to appear in this country, the virus is causing concern because it is highly virulent. About one-third of infected individuals have died from the disease. Currently, however, there is no evidence that the virus spreads easily within communities and the risk that MERS poses to the U.S. public remains low.

Most people who have been confirmed to have MERS have developed lower respiratory infections, including fever, cough, and shortness of breath. As of May 22, globally, 635 laboratory-confirmed cases of infection with MERS-CoV have officially been reported to the World Health Organization, including 193 deaths. Ages of those infected range from 2 to 94, according to the CDC. The virus appears to be most aggressive in people with underlying medical conditions.

The virus was first identified in Saudi Arabia. Other countries in the Arabian Peninsula with MERS cases include the United Arab Emirates (UAE), Qatar, Oman, Jordan, Kuwait, Yemen and Lebanon. The CDC recently issued an advisory for travel to countries in or near the Arabian Peninsula but does not restrict travel to that area or recommend that travelers change their plans because of MERS. This is because most cases of person-to-person spread have occurred in healthcare workers and other close contacts, such as family members and caregivers of people sick with MERS.

The CDC advises that travelers to these countries pay close attention to their health during and after their trip. They are urged to call a healthcare practitioner right away if they develop fever and symptoms of lower respiratory illness, such as cough or shortness of breath, within 14 days after travel and to inform their healthcare practitioner of the countries they visited before becoming ill.

The CDC recommends testing for any travelers with acute lower respiratory symptoms within 14 days of travel and for people who had close contact with someone diagnosed with MERS or someone who traveled to endemic areas and has MERS symptoms.

Diagnosis of MERS is made by detecting the virus in a sample of sputum or fluid from the lungs, which is the preferred sample, according to the CDC. Alternatively, a respiratory sample collected by swabbing the back of the nostrils or throat, a blood sample, or a stool sample can be tested. The samples are then analyzed using a method called PCR to see if a person is infected. In the U.S., testing is carried out by the CDC or state public health laboratories.

The MERS virus was first identified as a novel virus in 2012 and caused several new cases last year. CDC virologists say it is likely that the original source of the virus was an animal. In addition to humans, MERS has been found in camels in several countries, including Qatar, Egypt and Saudi Arabia, and in a bat in Saudi Arabia. CDC says more information is needed before it is known whether animals are the source of the virus and, if so, how they transmit it to humans.

The CDC continues to work with the World Health Organization to better understand the virus, how it is spread, ways to prevent spread, and the risk it poses to the general public. Meanwhile, the agency recommends that everyone follow the general recommendations for reducing infections:

  • Wash hands well and frequently
  • Cover your mouth and nose when sneezing or coughing
  • Avoid touching face, eyes, nose, mouth without washing hands
  • Avoid close contact with sick people
  • Wash surfaces frequently with disinfectant

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Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used. To access online sources, copy and paste the URL into your browser.

(Reviewed May 17, 2014). Centers for Disease Control and Prevention. Middle East Respiratory Syndrome (MERS). Available online at through Accessed May 18, 2014.

(Reviewed May 17, 2014). Centers for Disease Control and Prevention. Frequently Asked Questions on MERS. Available online at through Accessed May 18, 2014.

(May 21, 2014). Centers for Disease Control and Prevention. Travel Advisory, MERS in the Arabian Peninsula. Available online at through Accessed May 27, 2014.

(May 23, 2014). World Health Organization. Middle East Respiratory Syndrome Coronavirus (MERS-CoV) – Update. Available online at through Accessed May 27, 2014.

Centers for Disease Control and Prevention. Press Release: CDC concludes Indiana MERS patient did not spread virus to Illinois business associate. May 28, 2014. Available online at through Accessed May 29, 2014.