MERS infection confirmed in camels

Middle East respiratory syndrome, or MERS, coronavirus was confirmed in three camels belonging to a herd that was linked to two human cases of infection in Qatar. The evidence was recently published in Lancet Infectious Diseases.

However, researchers are unsure whether the two human cases were infected by camels or vice versa.

“Another possibility is that people and camels could have been infected from a third as yet unknown source,” Mohd M. Al-Hajri, MD, of the Supreme Council of Health in Qatar, and colleagues wrote. “While additional sequencing might provide improved resolution, it probably will not provide conclusive evidence. The important unknown is the exact timing of infections, both in the infected people and camels.”

Mohd M. Al-Hajri

After the two men became infected with MERS on a Qatari farm in October, Qatar health authorities, supported by members of WHO and the Food and Agriculture Organization of the United Nations, conducted an epidemiological investigation into the potential sources of exposure of the two patients.

Nose and rectal swabs and blood samples taken from 14 camels were sent to laboratories in the Netherlands, where they were tested using real-time PCR. Positive samples were tested again using MERS-specific PCRs and genetic sequencing and compared with the samples taken from the human cases.

MERS coronavirus was confirmed by three independent PCRs and genetic sequencing on the nose swabs of three camels, according to the researchers. Eight additional nose swabs tested positive for the virus on one or more PCR tests but could not be confirmed by genetic sequencing. The sequences from the confirmed samples were “very similar” to the MERS virus detected in the two human cases, but not identical.

All 14 camels had MERS neutralizing antibodies, indicating that the outbreak was in its late stages by the time investigators had taken samples.
AlHajri and colleagues suggested the possibility that the source of the infection may have been other livestock species, such as cattle, sheep or goats.

“While confirmation of the source is awaited, we recommend that a detailed case history is taken of any cases of MERS-[coronavirus], including review of any animal exposures (including animal products), and targeted (prospective) serosurveys to determine what risk factors are associated with human infection,” the researchers wrote.

In an accompanying editorial, Neil M. Ferguson, DPhil, and Maria D. Van Kerkhove, PhD, of the Medical Research Council Centre for Outbreak Analysis and Modelling at Imperial College London, said a better understanding of the role of animals in the transmission of MERS is needed to control the spread of the virus.

“The virus can spread from person to person, sometimes causing substantial outbreaks, but whether the virus is capable of self-sustained (ie, epidemic) human-to-human transmission is unknown,” they wrote. “If self-sustained transmission in people is not yet underway, intensive control and risk-reduction measures targeting affected animal species and their handlers might eliminate the virus from the human population.”

Mohd M. Al-Hajri, MD, can be reached at malhajri1@sch.gov.qa.

For more information:

Ferguson NM. Lancet Infect Dis. 2013;doi:10.1016/S1473-3099(13)70691-1.

Haagmans BL. Lancet Infect Dis. 2013;10.1016/S1473-3099(13)70690-X.

Disclosure: Study researchers Haagmans, Raj and Osterhaus have a patent pending for the MERS coronavirus. Osterhaus also is a scientific adviser for Viroclinics Biosciences.