Coronaviruses are enveloped RNA viruses. Coronavirus infections in humans most frequently cause symptoms of the common cold. Coronaviruses 229E and OC43 cause the common cold; the serotypes NL63 and HUK1 have also been associated with this syndrome.
Two coronaviruses, MERS-CoV and SARS-CoV, cause much more severe respiratory infections in humans than other coronaviruses. In 2012, the coronavirus MERS-CoV was identified as the cause of Middle East respiratory syndrome (MERS). In late 2002, SARS-CoV caused an outbreak of severe acute respiratory syndrome (SARS).
Middle East Respiratory Syndrome (MERS)
Middle East respiratory syndrome (MERS) is a severe acute respiratory illness caused by the newly identified MERS coronavirus (MERS-CoV).
MERS-CoV infection was first reported in September 2012 in Saudi Arabia, but an outbreak in April 2012 in Jordan was confirmed retrospectively. Between April 2012 and August 2013, 91 cases were laboratory-confirmed; 74 of them occurred in Saudi Arabia, where new cases continue to appear. Other cases have been confirmed in Qatar and the United Arab Emirates. Cases have also been confirmed in France, Germany, Italy, Tunisia, and the United Kingdom in patients who were either transferred there for care or became ill after returning from the Middle East. Person-to-person transmission has been established by the development of infection in people whose only risk was close contact with people who had MERS. Some infected patients, called superspreaders, have infected many contacts.
The reservoir of MERS-CoV is unknown; however, a closely related coronavirus was isolated from a bat.
The incubation period is about 5 days. More than half of cases have been fatal. Median patient age is 56 yr, and the male:female ratio is about 3:1. Infection tends to be more severe in elderly patients and in patients with a preexisting disorder such as diabetes, a chronic heart disorder, or a chronic renal disorder.
Fever, chills, myalgia, and cough are common. GI symptoms (eg, diarrhea, vomiting, abdominal pain) occur in about one third of patients.
In all patients, chest imaging detects abnormalities, which may be subtle or extensive, unilateral or bilateral. In some patients, levels of LDH and AST are elevated and/or levels of platelets and lymphocytes are low. A few patients have acute kidney injury. Disseminated intravascular coagulation and hemolysis may develop.
The WHO considers the risk of contracting MERS-CoV infection to be very low for pilgrims traveling to Saudi Arabia for Umrah and Hajj; last year's Hajj did not result in an increase of patients with MERS-CoV infection. For additional information about pilgrimages to the Middle East, see www.who.int/ith/updates/20130725/en/.
MERS should be suspected in patients who have an unexplained acute lower respiratory infection and either
The most recent recommendations are available from the WHO (Interim surveillance recommendations for human infection with novel coronavirus) and, in the US, the Centers for Disease Control and Prevention (Interim Guidelines for Investigation for Middle East Respiratory Syndrome (MERS)).
Testing should include real-time RT-PCR testing of lower respiratory secretions, ideally taken from different sites and at different times. Serum should be obtained from patients and from all, even asymptomatic close contacts, including health care workers (to help identify mild or asymptomatic MERS). Serum is obtained immediately after MERS is suspected or after contacts are exposed (acute serum) and 3 to 4 wk later (convalescent serum).
Treatment is supportive. To help prevent spread from suspected cases, health care practitioners should use standard, contact, and airborne precautions.
There is no vaccine.
Severe Acute Respiratory Syndrome (SARS)
Severe acute respiratory syndrome (SARS) is a severe, acute respiratory illness caused by the SARS coronavirus (SARS-CoV).
SARS is much more severe than other coronavirus infections. SARS is an influenza-like illness that occasionally leads to progressively severe respiratory insufficiency. SARS-CoV was first detected in the Guangdong province of China in November 2002 and subsequently spread to > 30 countries. As of mid-July 2003, > 8000 cases had been reported worldwide, with > 800 deaths (about 10% case mortality rate). This outbreak subsided, and no new cases have been identified since 2004.
Diagnosis is made clinically, and treatment is supportive.
Last full review/revision October 2009 by Ronald B. Turner, MD
Content last modified October 2013