The 10-day running total of new MERS cases in Saudi Arabia reaches 16 today, with the addition of three new `primary' cases, from three different localities All three are male, listed in stable condition, and have no known risk exposures.
This recent uptick in cases have been widely scattered across the Kingdom, with just 4 of the last 16 cases linked to camel exposure. One was listed as a household contact of a known case, while the remaining 11 are listed as `primary' cases with no known risk exposure.
The number and size of large nosocomial MERS outbreaks is down markedly in KSA in 2016, with just two of real note; one in the spring and one in early summer (see graph below).
This major improvement in Saudi hospital infection control has helped limit the number of new MERS cases to only 218 since the start of the year; less than half the number reported in 2015 (n=460).
The percentage of Healthcare acquired cases has dropped from 33% to 27% over the past 11 months. At the same time, the number of `primary' cases has jumped from 39% to 45%.
While a substantial percentage of these primary cases are linked - at least tentatively - to camel exposure (direct or indirect), for the vast majority no known risk exposure is ever identified.
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. A year ago, a study in the EID Journal: Risk Factors For Primary MERS-CoV Infection, Saudi Arabia, while finding camel exposure a major risk factor, wrote:
Other potential explanations of MERS-CoV illness in primary case-patients who did not have direct contact with dromedaries include unrecognized community exposure to patients with mild or subclinical MERS-CoV infection or exposure to other sources of primary MERS-CoV infection not ascertained in our study.For now, the role of mild or asymptomatic cases in spreading the virus remains suspected, but largely unproven.