Late Breaking News
A recent article in the New England Journal of Medicine drives home the importance of prompt reporting and response to limit spread of the disease, particularly in a hospital setting. Johns Hopkins researchers found that, in an outbreak this spring in Saudi Arabia, 21 of the 23 cases acquired MERS-CoV through person-to-person transmission in four healthcare facilities. Fifteen of the 23 total cases died, a 65% fatality rate.2
According to the researchers, “person-to-person transmission of MERS-CoV can occur in health care settings and may be associated with considerable morbidity. Surveillance and infection-control measures are critical to a global public health response.”
Early testing of suspected cases has shown significant benefit. The survival rate of patients identified by active surveillance during the outbreak was much higher (75%) than the survival rate of those identified clinically (16%), likely because “enhanced surveillance was more effective at detecting less severe disease than was identification of clinical features,” the authors wrote.
Clinical testing poses challenges, however. Validated serologic assays are not yet available, and throat swabs among patients in this cluster were occasionally negative.
“It is not clear whether sputum or nasopharyngeal samples might be superior to throat samples or whether virus is shed more abundantly later in the course of the illness or in more severe illness,” as it is in severe acute respiratory syndrome (SARS), according to the NEJM report.
AFHSC and WHO strongly recommend obtaining lower respiratory specimens for testing. If lower track specimens are not available or clinically indicated, clinicians should obtain both nasopharyngeal and oropharyngeal swab specimens. If patients strongly suspected to have MERS-CoV have an initial negative result, they should be retested.
The researchers noted that MERS-CoV had many similarities to SARS, including initial symptoms of nonspecific fever and mild, nonproductive cough that progresses to pneumonia and gastrointestinal symptoms in some patients. As with SARS, some MERS-CoV infected patients do not appear to transmit the disease at all, and some seem to be highly contagious.
The median incubation period for SARS is about four days with a serial interval of 8.4 days; for MERS-CoV, the researchers estimated median incubation of 5.2 days and a serial interval of 7.6 days.
MERS-CoV has a much higher fatality rate, however, at 55%, compared with an 8% to 10% fatality rate for SARS. So far, MERS-CoV has not had the rapid spread seen with SARS, which infected more than 8,000 people in nine months.
French researchers recently published a study in Lancet that concluded that MERS-CoV is unlikely to have pandemic potential, partly because it is so lethal.3
1. “Revised interim case definition for reporting to WHO — Middle East respiratory syndrome-coronovirus.” Global Alert and Response (GAR). WHO. July 3, 2013.
2. Assiri A, McGeer A, Perl TM, et al. Hospital outbreak of Middle East respiratory syndrome coronavirus. N Engl J Med 2013. Epub June 19, 2013.
3. Breban R, Riou J, Fontanet A. “Interhuman transmissibility of Middle East respiratory syndrome coronavirus: estimation of pandemic risk.” The Lancet. Epub ahead of print. July 5, 2013.