Laboratory testing for MERS-CoV remains a
challenge. Validated serologic assays are not yet
available, and this may have limited the identification
of cases. In this cluster, results of throat
swabs were occasionally negative and repeat testing
for MERS-CoV was required. 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
SARS.36 It seems prudent to conclude that one
cannot reliably rule out MERS-CoV disease on
the basis of a single negative test when a patient
presents with the appropriate clinical syndrome
and epidemiologic exposure. There is evidence
that repeat testing and tests on sputum orbronchoalveolar-lavage fluid are of value in improving
diagnostic accuracy.
The repeated introduction of the infection
into the community, the ongoing detection of
new illness, and the substantial impact of hospital
transmission in this outbreak underscore the
importance of investigations into the community
source of MERS-CoV. Without the ability to
prevent community infection, prevention of health
care transmission will remain a challenge. Outbreak-
control measures included precautions for
patients until 24 hours after symptoms resolved.
To date, the Ministry of Health has found no
evidence of transmission from patients in whom
precautions have been discontinued. Further investigations
to identify the duration of viral
shedding as well as the complete spectrum of
disease are needed to refine public health recommendations.