Via CIDRAP, Lisa Schnirring has a long, informative report: WHO sees camels as MERS source, but route uncertain. Excerpt:
Camels are the source of Middle East respiratory syndrome coronavirus (MERS-CoV), but it's still not clear how the virus is jumping to humans, the World Health Organization (WHO) said yesterday in a summary of its latest thinking on the disease, based on cases and scientific reports.
The agency also raised concerns about transmission of the disease in hospitals, which seems to be fueling a good portion of the limited human-to-human spread of the virus.
The WHO's fresh assessment came with a separate statement revealing more about six recent cases reported by Saudi Arabia and on the eve of yet another new case reported by the country's health ministry.
The new WHO review is its first on MERS since Jan 20. Since then, researchers have published three major animal studies, and health officials from five different Middle Eastern countries have reported 28 human infections, 10 fatal, to the WHO.
Clues from animal studies
Genetic sequencing conducted in two of the studies—one on camels in Egypt and one on an infected camel linked to a human case in Saudi Arabia—found high similarity to MERS-CoV viruses that have infected people.
In the third study, testing found evidence of the virus in a large number of camels across Saudi Arabia, but not in goats and sheep. The same study looked at archived specimens hinted that camels have been exposed to the virus as far back as 1992.
Genetic sequencing doesn't just show the similarity between the camel and human viruses, it also seems suggest that human disease patterns result from repeated introductions into human populations from camels, with only limited ongoing transmission in humans, the WHO said.
However, less clear is how the virus is transmitting from camels to humans. The WHO said that so far, its analysis of primary cases—those not infected by other humans—suggests that transmission is indirect, because most patients lack a recent history of direct contact with camels.