Epidemiologic and phylogenetic analyses support
person-to-person transmission; however, it
is not possible to be certain about whether there
were single or multiple introductions from the
community. Similarly, we are unable to determine
whether person-to-person transmission
occurred through respiratory droplets or through
direct or indirect contact and whether the virus
was transmitted when the contact was more
than 1 m away from the case patient. Because
some patients presented with gastrointestinal
symptoms, and transmission appeared to occur
between rooms on the ward, the current WHO
recommendations for surveillance and control
should be regarded as the minimum standards35;
hospitals should use contact and droplet precautions
and should consider the follow-up of persons
who were in the same ward as a patient
with MERS-CoV infection.
It is possible to explain all the episodes of
transmission in this outbreak by assuming that
patients were infectious only when they were
symptomatic; however, this does not rule out
transmission during the incubation phase or
during asymptomatic infection. Because this
was a retrospective investigation, we may have
missed exposures that were not documented or
that were forgotten; we may also have misclassified
community-acquired cases as health care–
associated cases. Our choice of the most likely
exposure to link patients may have been incorrect.
Despite these limitations, multiple iterations
of transmission mapping resulted in maps with
similar overall results.