Photo Credit WH
# 7819
Continuing with this week’s flood of new reports and summaries on the MERS Coronavirus (see these from the WHO, the ECDC, and the CDC’s MMWR) – yesterday the journal Eurosurveillance published a detailed look at the changing demographics of the first 133 diagnosed MERS cases.
Eurosurveillance, Volume 18, Issue 39, 26 September 2013
Taking stock of the first 133 MERS coronavirus cases globally – Is the epidemic changing?
P M Penttinen , K Kaasik-Aaslav, A Friaux, A Donachie, B Sudre, A J Amato-Gauci, Z A Memish, D Coulombier
Since June 2012, 133 Middle East respiratory syndrome coronavirus (MERS-CoV) cases have been identified in nine countries. Two time periods in 2013 were compared to identify changes in the epidemiology. The case-fatality risk (CFR) is 45% and is decreasing. Men have a higher CFR (52%) and are over-represented among cases. Thirteen out of 14 known primary cases died. The sex-ratio is more balanced in the latter period. Nosocomial transmission was implied in 26% of the cases.
Early on this disease was predominantly seen as affecting older males, and the ICU admission rate and case fatality ratio (CFR) was higher. Over the summer the male-female ratios, average patient age, and mortality rates have slowly shifted – although I’d be quick to caution that surveillance for mild and/or asymptomatic cases in Saudi Arabia (and elsewhere) is hardly optimal.
Quite frankly, we don’t know what we are missing. Calculations like mortality rates are based only on the cases that have been documented, and since those tend to be more serious presentations of any illness, they have the potential of being skewed.
Regarding mild or asymptomatic cases, this article reports:
Since June 2013, 18 asymptomatic or mildly symptomatic cases have been reported. All were without any symptom or very mild with one episode of fever with or without myalgia and chills. In SA, 16 asymptomatic cases were detected during screening of all contacts of diagnosed cases and were included if positive for two specific gene targets (upE and ORF1a) on polymerase chain reaction (PCR). The remaining two asymptomatic cases were detected in UAE.
Other demographic and epidemiological findings include:
The majority of reported cases are adult men and very few children or adolescents have been diagnosed with MERS-CoV infection (Table). The female to male ratio of cases is 0.67 overall. However, it increased in 2013 from 0.33 in March to May, to 1.08 in June to September.
We identified 14 clusters of 2-34 cases, where the primary cases were identified or suspected. However, data quality on the clusters is weak. All of the known 14 primary cases in clusters were adult men (24-83 years old) who were most likely exposed on the Arabian Peninsula. Of 129 cases with available information on transmission, 33 (26%) were possible nosocomial transmissions, 15 of these cases were healthcare workers (HCW). Seventeen of the 23 cases reported as HCW were female.
Of all reported 133 cases, 60 (45%) cases were admitted to intensive care (ICU). In comparison, between March and May 2013, 25 of 40 cases (63%) were admitted to ICU, while from June to September 2013, 25 of 77 cases (33%) were admitted to intensive care.
The overall CFR among the 133 cases is 45% on 25 September 2013. Among symptomatic cases the CFR decreased from 23 of 40 cases (58%) in March to May to 21 of 77 (27%) in June to September.
Men have a higher CFR compared with females (52 versus 24%) (Table). Among the known primary cases in clusters with available information on outcomes, the CFR is 93% (13/14).
Seventy-three per cent of the 55 fatalities had at least one comorbidity reported compared to 41% of 73 surviving cases. All deaths have been reported among adults except one in a two-year-old child.
Regarding these shifts in demographics, the authors write:
Our data point towards a changing pattern of cases compared with the previously published case series [2-13] and with the review of the first 47 cases detected in SA [29]. More women and cases without comorbidities are being reported. The increased proportion of asymptomatic cases and the decreased CFR may reflect enhanced surveillance catching cases having remained unnoticed at the early stages of the epidemic.
For now MERS cases remain sporadic, and largely confined to the Arabian peninsula. Small clusters involving human-to-human transmission have been reported, but community spread of the virus has not been documented.
There are concerns that the virus may be spreading, undetected among mildly affected or asymptomatic persons, but without good community seroprevalence studies the scope and extent of such transmission remains unknown.
While we are learning more each day about this virus, a year after MERS was first detected there remain many unanswered questions about this emerging disease.
- Where (what animal species) does it come from?
- How does it jump to human populations?
- What (if anything) changed recently to prompt or facilitate that jump?
- How widespread is it in the human population?
- What can be done to prevent its spread?
Compared to where we were - and how much we knew a year after the detection of SARS in 2003 - we have a long way to go to catch up. And with roughly 2 million religious pilgrims expected to visit the Saudi Kingdom next month for the Hajj, finding the answers to these (and other) questions takes on even greater urgency.
Stay tuned.
