Saudi Arabia's Ministry of Health (MOH) announced 6 new MERS-CoV cases over the past 3 days, including 3 in Riyadh and 3 fatalities, and in a new research development, experimental infection tests on Bactrian camels found that they are susceptible to the virus.
Cases include secondary infection in Riyadh
In epidemiologic week 22 updates, Saudi Arabia's health ministry reported six new MERS-CoV (Middle East respiratory syndrome coronavirus) cases from May 26 to May 28. Of the three Riyadh cases, one involves a 23-year-old woman whose exposure to the virus is listed a secondary, hinting at a potential household or hospital cluster.
The other two patients from Riyadh are a 65-year-old man who died from his infection and whose exposure is listed as primary, meaning he isn't thought to have contracted the virus from another known patient. The other is a 64-year-old man who had contact with camels before he got sick.
The Saudi MOH has now reported seven MERS-CoV cases in Riyadh in May.
The other cases in the ministry's latest updates are in three different cities: Medina, Najran, and Buraydah. The patient from Medina is an 80-year-old man who isn't thought to have contracted MERS-CoV from another patient. His exposure to camels isn't known and he died from his illness.
The patient from Najran is a 35-year-old man with primary exposure who died, and the patient from Buraydah is a 26-year-old man who isn't thought to have contracted the virus from a known case-patient and whose exposure to camels is unknown.
Saudi Arabia has reported 147 MERS-CoV cases this year. The World Health Organization (WHO) said in its most global update that it recorded 2,428 cases through Apr 30, at least 839 of them fatal. The vast majority of the illnesses have been in Saudi Arabia.
Bactrians show similar infection, shedding patterns
Dromedary (one-humped) camels are known to be the major source of zoonotic MERS-CoV transmission, but not much is known about the susceptibility of the double-humped Bactrian camel population, which partly overlaps that of dromedary camels in west and central Asia. So far, serology studies in Bactrian camels haven't found evidence of the virus, which could mean the virus isn't circulating in the animals or that they aren't susceptible to it.
To explore susceptibility in Bactrian camels, a research team based at the National Institute of Allergy and Infectious Diseases (NIAID) Rocky Mountain Laboratories in Hamilton, Montana, experimentally infected two male camels that were housed in an animal biosafety level 3 facility. They reported their findings May 23 in Emerging Microbes and Infection.
After intranasal inoculation with MERS-CoV, the investigators collected nasal swabs from both animals on the first 5 day after inoculation, and from one of the camels at weekly intervals through the 28th day after inoculation. Both camels were euthanized, one 5 days after and one 28 days after inoculation, and the researchers examined and tested their tissues.
The animals developed mainly an upper respiratory illness, and though clinical signs were benign, the Bactrian camels shed large quantities of MERS-CoV, similar to what scientists have observed with dromedary camels, suggesting that the Bactrians are susceptible to the virus. "Moreover, the virus shedding kinetics of MERS-CoV in Bactrian camels was virtually identical to previous experimental studies in dromedary camels," the team wrote.
Also, the investigators found that the DPP4 receptor for MERS-CoV in Bactrian camels was 98.3% similar to that of dromedary camels. It was 100% similar for 14 residues that interact with the MERS-CoV spike receptor.
They concluded that if MERS-CoV were introduced to Bactrian camel populations, the animals could act as a reservoir, similar to dromedaries and possibly exposing humans to infection.
See also:
May 28 Saudi MOH epidemiologic week 22 report
May 23 Emerg Microb Infect study
