MERS is Widespread in Saudi Arabia

Middle East Respiratory Syndrome (MERS) has infected at least 1370 individuals (including asymptomatic cases) in Saudi Arabia since 2012 (e.g. ProMED link). Since mid-February 2016, Buraidah in Al Qassim region in Saudia Arabia has been experiencing a local MERS outbreak with 23 cases reported through March 16, 2016 (link). As of April 3, 2016 there have been an additional 11 cases reported, bringing the total cases reported from Buraidah by Saudi Arabia Ministry of Health to 34.  Many of these cases are a result of nosocomial infection, but perhaps as many as eight of these cases were community acquired infections with some individuals having contact with animals. Among these 34 cases, 17 have been reported as deaths so far. (see note)

While the Buraidah MERS outbreak has raised concerns, the 34 cases from Buraidah represented about 40% of all MERS cases reported from Saudi Arabia since January 1, 2016. The majority of MERS cases since January 1, 2016, about 49 cases, have been reported from numerous other locations around Saudi Arabia as shown in the map below. 

Since January 1, 2016, human MERS cases have been reported from at least 23 populated places scattered across Saudi Arabia. The widespread geographic distribution of these cases suggests that MERS has now become endemic in Saudi Arabia.

 Note: The total cases from Buraidah include a 60 year-old male who experienced symptom onset in Hail and was treated in the Buraidah hospital where he died (Case No 3. DON March 21,  2016)

Case Details from the Current MERS Outbreak in Riyadh Saudi Arabia, August 2015

The current outbreak in Riyadh started mid-July when a 56-year-old man became infected with Middle East Respiratory Syndrome coronavirus (MERS). This individual had frequent contacts with camels and consumed raw camel milk. This man infected his 52-year-old wife, his 53-year-old brother, and 30-year old son. The index case and his wife are reported to have died.

Almost 120 cases have been confirmed during this MERS outbreak in Riyadh through August 28, 2015.  As in other MERS outbreaks, more males then females are infected, about 61%. The males range in age from 2-109 years old with a median age of 61. The females range in age from 25 to 98 with a median age of 58.

The fatality rate for this outbreak is about 25%, with similar death percentages for both males and females. However the fatality statistics could change because the Saudi Arabia Ministry of Health is reporting that there are at least 50 cases still under treatment.

In this outbreak, most of the infections had been contracted by either visiting or being treated in a hospital with current MERS patients. A few cases are reported to have contact with confirmed MERS patients possibly outside of a healthcare setting. Information on family clusters is not available. It is difficult to assess the extent of family clusters, since that information is not generally available. 

Besides the initial family cluster in this outbreak, one other possible family cluster can be proposed from the data. A 56-year-old female experienced symptom onset on August 7, with her death reported on August 17. The World Health Organization reports that a 28-year-old female had contact with this woman and became symptomatic on August 12. A third individual, a two-year-old boy, also had contact with this woman and became symptomatic on August 12 as well. The boy is reported by the Saudi Arabia Ministry of Health to have recovered. Speculating, this cluster would seem to be a result of a daughter and a grandson interacting with the 56-year-old grandparent.

Healthcare workers represent about 11% of all infected individuals in this current outbreak.  This is similar to the overall percentage of healthcare workers infected with MERS in Riyadh since 2012. About 10% of all of MERS cases reported from Riyadh since 2012 were healthcare workers.

The epidemiological similarities among various MERS outbreaks should begin to provide a framework for understanding and controlling this disease in the future.

Where are the pediatric cases of MERS Infections?

Prior to the report of the Middle East Respiratory Syndrome (MERS) outbreak in the Republic of Korea (South Korea) in mid-May, more than 1000 cases of MERS had been reported from around the world since 2012. Most of these cases, about 87%, have been reported from the Kingdom of Saudi Arabia (Saudi Arabia). Only about 3% of the MERS cases reported through mid-May from Saudi Arabia can be can be classified as pediatric cases (cases less than 18 years old). There has been speculation that Saudi Arabia has had pediatric cases of MERS that were unreported (link).

Through June 14, 2015, South Korea has reported 150 MERS cases. The number MERS cases reported from South Korea is second only to Saudi Arabia. Since the beginning of the outbreak in South Korea only a single pediatric MERS case has been reported, a hospitalized, 16-year-old male.

As unfortunate as the outbreak in South Korea is, it provides an important data set for analyzing the nature of MERS infections. The South Korea outbreak was caused by a single individual (index case) who was infected on the Arabian Peninsula and returned to South Korea. Unlike the Arabian Peninsula, there is no evidence that any animal species on the Korean Peninsula is infected with or could transmit the MERS coronavirus to humans. The infection of all 150 cases in South Korea is a direct result of human-to-human transmission that can be traced back to the initial index case.

A risk assessment from the European Centre for Disease Prevention and Control (ECDC) (link) provides a graph showing the relationship of age groups of MERS cases distinguished by gender for about 200 cases from Saudi Arabia since the beginning of 2015 and the 107 cases from South Korea since the MERS outbreak began. The graphs seem to show a comparable age distribution of infected individuals from South Korea and Saudi Arabia in 2015. A more rigorous statistical comparison can be developed by comparing the age distribution of the currently confirmed 150 cases from South Korea with the most recent 150 MERS cases reported by the Saudi Arabia Ministry of Health (150 cases since February 15, 2015).

The table and graph below present the count and percentages of MERS cases by10-year age groups for these two countries. The table and graph demonstrate that there is a high correspondence in MERS cases by age category between South Korea and Saudi Arabia. In fact, these two age-category distributions of infected individuals, separated geographically by almost 7500 km, are highly correlated with an R value of .95. But, what can we learn from this table and what does this correlation tell us?

First, it tells us that pediatric cases are rare in South Korea, and by extension, they are also rare in Saudi Arabia. Second, the high correlation coefficient, along with few pediatric cases in both countries, indicates that Saudi Arabia is not hiding or covering up pediatric cases of MERS. Third, its tells us that MERS seems to be differentially infecting adults compared to children or adolescents. Why this is the case is not clear.

It is important to reiterate that all of the MERS cases in  South Korea are a result of human-to-human transmission. None of the MERS cases in South Korea are a result of the coronavirus jumping from an animal host to humans. The outbreak in South Korea is shedding light on the nature of the MERS coronavirus and how it affects and transmits among humans.

WHO provides additional data on MERS cases from Saudi Arabia in October

Earlier this month, I noted that the World Health Organization (WHO) did not report information on five MERS cases from Saudi Arabia from October  (see Has WHO overlooked 5 MERS cases in Saudi Arabia?), although theses cases were counted in the world-wide total in the Disease Outbreak News posted on November 7, 2014 (link).

Two days ago, the WHO provided additional details about these five cases (link)  that are not available on the statistics page of the Saudi Arabia Ministry of Health website. The reporting of these additional case details is important to understanding the nature of human MERS infections.

Since, the last WHO update on MERS from Saudi Arabia (through October 30, 2014), the Saudi Arabia Ministry of Health website has reported almost 20 new MERS cases (link),. Hopefully, WHO will publish details about these cases soon as well.

Has WHO overlooked 5 MERS cases in Saudi Arabia?

Previously, I discussed discrepancies between the MERS case counts for the World Health Organization (WHO) and the European Centre for Disease Prevention and Control (ECDC) (link). The WHO case count differed from the number posted on the Saudi Arabia Ministry of Health website by 15 cases. At least 12 cases previously announced by the Saudi Arabia Ministry of Health had not yet been posted in Disease Outbreak News by the WHO through October 21, 2014.

Yesterday the WHO reported in aggregate 12 new MERS cases from Saudi Arabia from the period October 18 to October 26, 2014 (link). These 12 cases do not equate to the 12-case differential noted in my previous post. The most recent WHO report regarding cases from Saudi Arabia (October 16 link) only enumerates cases through October 11, 2014. However, between October 12 and October 16, the Saudi Arabia Ministry of Health website announced five additional MERS cases, Taif (3), Riyadh (1), and Al Karj (1).

Hopefully, the WHO will report these cases in the future or discuss why they are not included in the total count for MERS cases from around the world.

Links to five Saudi Arabia MERS Cases (October 12-16)

http://www.moh.gov.sa/en/CCC/PressReleases/Pages/Statistics-2014-10-12-001.aspx

http://www.moh.gov.sa/en/CCC/PressReleases/Pages/Statistics-2014-10-13-001.aspx

http://www.moh.gov.sa/en/CCC/PressReleases/Pages/Statistics-2014-10-14-001.aspx

http://www.moh.gov.sa/en/CCC/PressReleases/Pages/Statistics-2014-10-16-001.aspx (2 cases)

Another Cluster of MERS cases in Saudi Arabia

In the past several days, the Ministry of Health in Saudi Arabia has announced two new cases of Middle East Respiratory Syndrome (MERS), both from the city of Dammam in eastern Saudi Arabia. One is a 69 year-old male and the other is a 52 year-old female. Neither are health care workers and both are hospitalized.  The relationship between these two cases is not reported, however, these case could signal another local MERS outbreak in Saudi Arabia.

http://www.moh.gov.sa/en/CCC/PressReleases/Pages/Statistics-2014-08-25-001.aspx

http://www.moh.gov.sa/en/CCC/PressReleases/Pages/Statistics-2014-08-26-001.aspx

Another reported MERS infection in Saudi Arabia

Yesterday, Saudi Arabia reported a new case of Middle East Respiratory Syndrome (MERS) infection, a 72-year-old male from Riyadh. (link) This is the first MERS infection reported from Saudi Arabia since July 10 (link) and the first MERS cases reported for Riyadh since July 7. (link)

Because the incubation period of MERS is reported to be between 5 and 14 days, and assuming the Saudi Arabia Ministry of Health is reporting all MERS infections in the country, this newly reported case does not seem to be a result of human-to-human transmission but rather an independent infection most likely from a non-human animal source. It is unlikely, but possible, that this individual contracted the coronavirus from an asymptomatic human carrier. There is no reason to believe that this case resulted from a deliberate release of the coronavirus. See The discrepant epidemiology of Middle East respiratory syndrome coronavirus (MERS-CoV) for a hypothesis that MERS infections are a result of a bio-terrorist plot.