September 19, 2013
MERS Cases Jump By 18, WHO Revises Lab Testing Recommendations
Lawrence LeBlond for redOrbit.com - Your Universe Online
The Middle East respiratory syndrome (MERS) coronavirus continues to spread, with more than a dozen new laboratory-confirmed cases being reported to the World Health Organization (WHO) since September 1, 2013.
All patients are reported from Hafar Al-Batin, Medina and Riyadh. The ages of all patients range from three to 75 years old. The cases were reported to the WHO on Sept. 1, 5, 8, 10 and 11, 2013.
Saudi Arabia’s Ministry of Health also reported to the WHO an additional two deaths from MERS-CoV. The Ministry of Health also informed the WHO of one additional death from a previously lab-confirmed case; the patient died on September 6.
According to AFP, Saudi’s Health Ministry reported the death of a 75-year-old woman, who had chronic illness, died in Medina, while an 83-year-old man, who also had chronic disease, died in the country’s capital city.
The new reports bring the worldwide total number of MERS-CoV cases to 132, with 58 deaths. Interestingly, the mortality rate has dropped some since earlier reports. As late as mid-June, mortality was seen at more than 50 percent. With the latest number of cases in the books, mortality rate has seemingly dropped to below 44 percent.
Due likely to the increasing number of cases of MERS-CoV and the fact that experts have yet to get a handle on the origins of the disease, the WHO offered newly revised recommendations on lab testing for MERS-CoV.
The new recommendations also encourage caution with the use of serologic tests -- diagnostic identification of antibodies in plasma serum -- because they have yet to be extensively validated, according to University of Minnesota’s CIDRAP editor Robert Roos.
The latest recommendations are an update to guidance released by the WHO last December. Much like the earlier version, the new recommendations advise use of lower respiratory tract specimens for testing, mostly because they contain the highest viral load, but also advise that upper respiratory tract samples should be collected when possible.
The WHO also encourages sampling from multiple sites to increase the likelihood of finding the virus, potentially giving more clues to the origin of MERS-CoV. It noted that currently there is little information that testing whole blood is of any value.
As for serological testing, several tests have been published and the US Centers for Disease Control and Prevention (CDC) has developed a two-stage process for detecting antibodies, according to the WHO. However, the group adds, "All serological tests developed thus far have been validated only against a small number of convalescent sera from MERS CoV cases and it has not yet been possible to compare the performance of the different assays. No kits are currently available for serological testing."
The new recommendation advises that “any positive result by a single serologic test should be confirmed with a virus neutralization assay.” It adds that “there is no clear consensus on the interpretation of serologic findings in individuals and calls for a cautious approach when confirming cases on the basis of serologic testing.”
"For the time being, cases where the testing laboratory has reported positive serologic test results in the absence of PCR [polymerase chain reaction] testing or sequencing, are considered probable cases of MERS-CoV infection, if they meet the other conditions of that case definition," the WHO recommends.