MERS-CoV: Healthcare Workers Infected, Not All Cases Serious

Laurie Barclay, MD

August 08, 2013

Of 7 healthcare workers (HCW) in Saudi Arabia with Middle East respiratory syndrome coronavirus (MERS-CoV) infection identified by nasopharyngeal swab screening, 2 were asymptomatic and 5 had mild upper respiratory tract symptoms, according to a letter to the editor published online August 7 in the New England Journal of Medicine. To date, most of the 94 cases reported in the overall population have been in Saudi Arabia.

"Patients with [MERS-CoV] infection have presented with serious respiratory disease and have required hospitalization," write Ziad A. Memish, MD, from the Ministry of Health in Riyadh, Saudi Arabia, and colleagues. "However, there have been case reports of less severe disease within family and hospital clusters, and the clinical spectrum of MERS-CoV infections may extend to asymptomatic and subclinical cases. Therefore, the epidemiologic and clinical characteristics of this infection need further definition."

Transmission appears to occur through droplets or contact, according to patterns of spread of MERS-CoV among family or hospital clusters. HCW may particularly be at risk because of handling of sputum, respiratory secretions, feces, urine, and/or blood. Persons with asymptomatic or subclinical MERS-CoV infections in the community or in healthcare settings could result in transmission to close contacts or to patients with comorbid conditions.

In Saudi Arabia, the Ministry of Health routinely screens all close contacts of cases with MERS-CoV infection, with more than 3000 people screened to date.

Of the 7 cases recently identified and described in this letter, 2 were asymptomatic, 1 had only a runny nose, and 4 had mild upper respiratory tract symptoms. All were previously healthy female nurses with the exception of 1 person, who had diabetes.

Investigators screened single nasopharyngeal swabs, using a real-time reverse transcriptase–polymerase chain reaction amplification tests for the upstream E protein gene and for open reading frame 1a. Confirmed MERS-CoV infection was defined as having both assays positive. Six of the 7 HCW tested positive for MERS-CoV on day 2 and negative on day 3, but 1 remained positive until day 8.

Exposure was maximal in some of the nurses who did not completely follow infection control procedures. None of the nurses required treatment, all recovered fully within a week and remained healthy at follow-up, and no subsequent cases of MERS-CoV were associated with these cases.

The possible infectiousness of biological samples and their cross-transmission through contaminated surfaces and medical devices to the hands of HCW are still unclear. The investigators urge hospitals that provide care for patients with suspected or confirmed MERS-CoV infection to take appropriate measures to reduce transmission risk to other patients, HCW, and visitors.

"The identification of asymptomatic and subclinical cases of MERS CoV infection in [HCW] brings to light the urgent need to develop a rapid, sensitive, and specific diagnostic test and to conduct studies to accurately define the clinical spectrum of MERS-CoV infection," the authors conclude. "Maintaining a high awareness of the possibility of MERS-CoV infection and rapidly initiating infection-control measures are important strategies for controlling nosocomial transmission. [HCW] should be reminded of the importance of systematic implementation of infection-prevention and infection-control measures."

The authors have disclosed no relevant financial relationships.

N Engl J Med. Published online August 7, 2013. Full text

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