A letter appearing today in the New England Journal of Medicine describes mild and asymptomatic cases of MERS-CoV (Middle East respiratory syndrome coronavirus) in seven female Saudi Arabian nurses, further solidifying the evidence that the illness can be other than severe.
The letter, by two Saudi health officials and a British expert, says two of the nurses had no symptoms and the others had only mild ones, and all recovered without treatment. Further, the nurses apparently did not pass the virus to anyone else.
Until recently, most confirmed MERS cases have been severe; 46 of the 94 cases recognized by the World Health Organization have been fatal. But at least 16 asymptomatic cases have been reported since mid June, along with several mild cases.
Health officials are anxious to define the full range of clinical disease associated with MERS-CoV. One of the reasons is the concern that asymptomatic carriers of the virus may unwittingly pass the virus to others.
The letter says the nurses' cases were identified through screening of close contacts of confirmed MERS-CoV patients by means of polymerase chain reaction testing of nasopharyngeal swabs. The nurses, who all worked at different hospitals, ranged in age from 28 to 56, with a mean of 42.7. All were previously healthy except one, who had diabetes.
All seven had some level of exposure to MERS-CoV patients, and six of them were present during aerosol-generating procedures. Their compliance with infection control precautions was spotty, and some had "maximal exposure." They had no history of exposure to animals or to MERS-CoV cases in the community.
Of the five nurses who had mild symptoms, one had only a runny nose. "They did not require treatment, recovered fully within a week, and remained healthy on follow-up," the letter states.
The authors say no subsequent MERS cases were associated with the nurses. However, earlier this week, Saudi health officials reported in another journal that a Saudi man contracted MERS-CoV from an unknown source in a hospital while being treated for an unrelated condition. That report suggested that unrecognized mild or asymptomatic cases may be a more important contributor to transmission than previously thought.
The NEJM letter states, "The identification of asymptomatic and subclinical cases of MERS-CoV infection in health care workers 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 add that vigilance for the possibility of MERS cases and rapid implementation of infection prevention measures are important for controlling nosocomial transmission.
Memish ZA, Zumla AI, Assiri A. Middle East respiratory syndrome coronavirus infections in health care workers. (Letter) N Engl J Med 2013 (early online publication Aug 7) [Full text]
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