Via CIDRAP, Robert Roos writes: WHO revises guidance on MERS case-control studies. Excerpt:
In the wake of its recent conclusion that camels are probably fueling Middle East respiratory syndrome coronavirus (MERS-CoV) cases in humans, the World Health Organization (WHO) has revised its guidance for case-control studies to ascertain exactly how the virus is getting into people.
The 22-page guidance is designed to equip investigators to compare MERS case-patients with other people who don't have MERS, with the aim of identifying what factors might have caused exposure to the virus. The revision includes many questions about contact with animals, especially camels.
The lack of case-control studies has been cited by experts as a major gap in the response to MERS-CoV. It's not clear if any of the Middle Eastern countries most affected by MERS have launched a case-control study as yet.
In its Mar 27 summary of MERS developments, the WHO said, "Recent studies support the premise that camels serve as the primary source of the MERS-CoV infecting humans and that other livestock are not involved."
It said that available genetic data show the MERS-CoV isolates in camels and humans are closely linked and "suggest the current observed pattern of disease in humans is the result of repeated introductions into human populations from camels, with subsequent limited human-to-human transmission, rather than sustained community transmission among humans. As such, discovery of the route of transmission between camels and humans remains critical to stopping the initial introduction into human populations."
Multinational effort wanted
The case-control study guidance, dated Mar 28, was completed at a meeting in Riyadh on Mar 1 and 2 and was distributed to affected countries after the meeting, according to the WHO.
The stated goals of the guidance are to "identify modifiable non-human exposures that lead to human MERS-CoV infection" and describe other risk factors for infection, such as pre-existing medical conditions.
Investigation should focus on primary (index or sporadic) cases, meaning those in patients with no recent exposure to other confirmed or probable MERS patients, the document says.
"The study should be a multinational effort combining standardized data from all participating countries," it states. "Implementation will be supported by an international team of experts and national focal points that will jointly resolve issues and questions regarding implementation by consensus."
Anthony W. Mounts, MD, the WHO's MERS-CoV technical lead, recently told CIDRAP News that the agency would like to see the case-control study "include some retrospective cases but also enroll new cases as they occur."
He said the study would be carried out by the affected countries, with the WHO in a strictly advisory role.