After reporting no new cases yesterday, today the Saudi MOH announced 2 additional asymptomatic HCW infections in Domat Al Jandal, bringing the number of Saudi cases reported this month to 18.
Additionally, two previously announced cases have died.
Seven of the eleven (63%) Domat Al Jandal cases have been listed as asymptomatic, something we are seeing reported more often over the past year or so. Prior to 2016, it was estimated that only about 10% of cases were asymptomatic.
Most of those were detected through RT-PCR testing of close contacts of symptomatic patients, although until summer of 2015, the Saudi MOH didn't appear to be aggressively looking for asymptomatic cases.
That changed nearly two years ago after the WHO Statement On The 10th Meeting Of the IHR Emergency Committee On MERS rebuked the Saudis for their handling of asymptomatic cases (among other issues).
Since then, the Saudis have been far more diligent in seeking out, and reporting, asymptomatic cases. But this does make it difficult to compare rates today to rates reported in previous years.Like most viral infections, MERS-CoV can produce a wide range of illness, and so it is likely that many mild or asymptomatic cases go undetected. In 2013, we looked at a study published in The Lancet Infectious Diseases, that estimated for every case identified, there are likely 5 to 10 that go undetected.
Last year, in EID Journal: Estimation of Severe MERS Cases in the Middle East, 2012–2016, we saw a study that suggested the number of severe cases is 2.3-times higher than the total number of all laboratory-confirmed cases combined (including mild and asymptomatic) cases in the region.Since the source of many community acquired cases remains unknown, and asymptomatic carriage and transmission is viewed as a plausible - if not yet proven - explanation, a better understanding of the role of asymptomatic cases in spreading the MERS virus is badly needed.