As the chart above (courtesy of Dr. Ian Mackay’s VDU Blog) illustrates – even though we are just over halfway through the month of February - this month is already the fourth most active month for MERS cases on record (n=41).
Although we track the daily numbers via the Saudi MOH announcements, those reports are represented by charts, and contain few epidemiological details, and so we rely heavily on the follow up reports from the World Health Organization for more insight.
Today’s report covers 5 cases reported between 10 and 12 days ago – just a few days before the surge which began on the 11th. As you will see, of the five cases detailed, one had contact with camels (which may, or may not have led to infection), and another attended a wedding party.
But none of them had other history of exposure to known risk factors in the 2 weeks prior to the onset of symptoms. First the WHO GAR report (emphasis mine), then I’ll return with a bit more.
Middle East respiratory syndrome coronavirus (MERS-CoV) – Saudi Arabia
Disease outbreak news
16 February 2015
Between 5 and 7 February 2015, the IHR National Focal Point for the Kingdom of Saudi Arabia (SAU) notified WHO of 5 additional cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection. Cases are listed by date of reporting, with the most recent case listed first.
Details of the cases are as follows:
- A 50-year-old female from Najran city developed symptoms on 31 January and was admitted to a hospital on 5 February. The patient has comorbidities. She attended a wedding party in the 14 days prior to the onset of symptoms. The patient has no history of exposure to other risk factors in the 14 days prior to the onset of symptoms. She was admitted to ICU and is currently in critical condition.
- A 57-year-old male from Riyadh city developed symptoms on 25 January and was admitted to a hospital on 29 January. The patient has comorbidities but no history of exposure to any known risk factors in the 14 days prior to the onset of symptoms. He was admitted to ICU and is currently in critical condition.
- A 49-year-old male from Dammam city developed symptoms on 2 February and was admitted to a hospital on 4 February. The patient has comorbidities but no history of exposure to any known risk factors in the 14 days prior to the onset of symptoms. He was admitted to ICU and is currently in critical condition.
- A 62-year-old male from Riyadh city developed symptoms on 30 January and was admitted to a hospital on 4 February. The patient has comorbidities. He owns camels and has a history of frequent contact with them and consumption of raw camel milk. The patient has no history of exposure to other known risk factors in the 14 days prior to the onset of symptoms. He was admitted to a negative pressure isolation room on a ward and is currently in stable condition.
- A 34-year-old, non-national male from Riyadh city developed symptoms on 31 January and was admitted to a hospital on 3 February. The patient has no comorbidities and no history of exposure to any known risk factors in the 14 days prior to the onset of symptoms. He was admitted to a negative pressure isolation room on a ward and is currently in stable condition.
Contact tracing of household contacts and healthcare contacts is ongoing for these cases.
The IHR National Focal Point for the Kingdom of Saudi Arabia also notified WHO of the death of 1 previously reported MERS-CoV cases. The case was reported in a previous DON on 11 February (Case n. 5).
Globally, WHO has been notified of 983 laboratory-confirmed cases of infection with MERS-CoV, including at least 360 related deaths.
Nearly 3 years after the first known outbreak (April 2012) at Jordanian hospital, and 30 months since the virus was identified in Saudi Arabia, and we still don’t have a good understanding of how the virus is being transmitted in the community.
Zoonotic transmission – probably from camels – appears likely, but only represents a small percentage of infections. From there, patients often end up in the hospital, where nosocomial transmission is all-too-common, and we’ve seen some very large healthcare associated clusters.
But hospital-acquired infections only account for part of the picture.
We continue to see many cases arise in the community without any history of exposure to known risk factors (hospital or community exposure to known cases, animal exposure), begging the question – How were they infected?
The question of `asymptomatic’ transmission of the virus has yet to be answered, although we’ve seen hints that it may be a factor (see Study: Possible Transmission From Asymptomatic MERS-CoV Case).
Roughly 20% of known MERS cases are described as being mild (or asymptomatic), and so it isn’t far-fetched to think there are undiagnosed cases in the community, stealthily spreading the virus.
Normally we’d get answers to these questions from a a case-control study, where epidemiologists would compare laboratory-confirmed cases to a large number of controls, matched for age, sex, and by neighborhood.
By examining their respective exposures against their outcomes, patterns of risk are often revealed.
In the summer of 2013 the World Health Organization published a framework for just such a project on MERS (see case-control study protocol), and entreated the Saudi Ministry of Health to conduct, and publish, the study. While repeated promises have been made (see KSA Announces Start To Long-Awaited MERS Case Control Study), for whatever reason, we’ve yet to see the results.
For now the World Health Organization (in their February 5th WHO Summary & Risk Assessment On MERS-CoV) advises:
Can we expect additional cases of MERS-CoV infection in the Middle East? And can we expect additional cases exported to other countries?
WHO expects that additional cases of MERS-CoV infection will be reported from the Middle East, and it is likely that cases will continue to be exported to other countries by tourists, travellers, migrant workers or pilgrims who might acquire infection after exposure to an animal (for example, while visiting farms or markets) or human source (possibly in a health care setting). Until more is understood about mode of transmission and risk factors for infection, cases resulting from zoonotic transmission will continue to occur, and will eventually lead to limited community transmission within households and possibly significant hospital-associated outbreaks. Among the recently exported cases who reported performing Umrah in SAU, investigation into their activities while in SAU revealed that they had either visited a healthcare facility or had come into contact with camels or raw camel products while in SAU.