Middle East respiratory syndrome (MERS)

Case definition for reporting to WOAH

(Update: January 2019)


Middle East respiratory syndrome (MERS) is a viral respiratory infection of humans and dromedary camels which is caused by a coronavirus called Middle East Respiratory Syndrome Coronavirus (MERS-CoV).

Dromedary camels (Camelus dromedarius) have been confirmed by several studies to be the natural host and zoonotic source of the MERS-CoV infection in humans. Other species may be susceptible to infection with MERS-CoV. However, their epidemiological significance has not been proven.

MERS-CoV has been associated with mild upper respiratory signs in some dromedary camels. While the impact of MERS-CoV on animal health is very low, human infections has a significant public health impact.

Positive RT-PCR results for MERS-CoV or isolation of the virus from dromedary camels is notifiable to the WOAH because MERS is an emerging disease with a significant public health impact to human. The aims of reporting to the WOAH are to mitigate the human health risk of MERS-CoV and to prevent international spread, while ensuring safe international trade of dromedary camels and their products.

Confirmed case

The following defines a laboratory confirmed case of MERS-CoV infection (with or without clinical signs):

  1. MERS-CoV has been isolated from a dromedary camel; OR
  2. Viral nucleic acid has been identified in a sample from a dromedary camel on:
    a.    at least two specific genomic targets; OR
    b.    a single positive target with sequencing of a secondary target; OR
    c.    a single positive target and tested positive to rapid MERS-CoV antigen test

Additional notes

A case can be suspected based on a direct epidemiological link with a confirmed human case, living or traveling together in close proximity to a MERS-CoV infected dromedary camel or sharing the same environment with an individual dromedary infected with MERS-CoV. If testing for MERS-CoV is unavailable, negative or inconclusive on a single inadequate specimen, the case should also be suspected. Inconclusive tests may include a positive screening test on a single real time RT-PCR target without further confirmation. Animals with an inconclusive initial test should undergo additional sampling and testing to determine if the animal can be classified as a confirmed MERS-CoV case. Preference should be a repeat nasopharyngeal specimen. Other types of clinical specimens could also be considered for molecular testing if necessary, including blood/serum, and stool/rectal swab. These generally have lower titres of virus than respiratory tract specimens but have been used to confirm cases when other specimens were inadequate or unobtainable.