Wednesday, January 20, 2016

The Geography of MERS

Since 2012, the World Health Organization (WHO) has been notified of 1626 laboratory-confirmed cases of Middle East Respiratory Virus Syndrome (MERS) as of January 7, 2016 (link). These cases have been reported from 26 countries as shown on the map and table below. Cases have been reported from most continents: North America, Africa, Europe, and Asia. No cases have been yet been reported from South America, Australia, or the sparsely inhabited Antarctica. More than 75% of these cases have been reported from Saudi Arabia. 

Countries Reporting MERS infections to WHO
Worldwide count of MERS cases  

The earliest cases of MERS in 2012 were geographically associated with countries in the Middle East. Numerous cases in Saudi Arabia are reported as “primary cases”, autochthonous cases, which have been infected from local animal hosts. Current research indicates that camel populations on the Arabian Peninsula are a reservoir for this coronavirus, although there may be other intermediate animal hosts as well. 

The map above only shows countries that have officially reported MERS cases to WHO, not the countries where the individual cases were initially infected. A review of the published case reports indicates local infections from animal sources has only occurred in countries on or adjacent to the Arabian Peninsula as shown in the map below. Although the MERS jump from animals to human appears to be occurring only in a small geographic region in the Middle East, this coronavirus is very infectious. Many infections on the Arabian Peninsula and elsewhere are reported to have occurred from human-to-human contact or by transmission within a healthcare facility. 

Secondary cases of infections have occurred in health care facilities in Saudi Arabia, South Korea, and other countries. The large number of MERS infections among healthcare workers, healthcare facility patients, and patient visitors is a strong indication of the infectious nature of this coronavirus. According to published information, at least 240 reported MERS cases were healthcare workers.

Last year in South Korea, 185 cases of MERS were sparked by a single infected individual who traveled to South Korea from the Middle East. The infections spread primarily though hospitals. The nature of infectious transmission in health care settings is not clear. Human-to-human airborne transmission has been proposed for pneumonia-infected “superspreaders” in South Korea (link), but human-to- fomite-to-human transmission seems to occur frequently as well. 

Because of the nature of international travel and the infectious nature of this coronavirus MERS, cases have been reported from 26 countries around the world in less than four years. We can expect more MERS cases to be infected in the Middle East and to be reported from more countries in the future. 

Countries on the Arabian Peninsula reporting autochthonous cases of MERS 

Sunday, January 10, 2016

Will H5N6 Cause the Next Pandemic?

Influenza A(H5N6) is an emerging novel avian influenza that apparently derived from a reassortment of A(H5N1) with A(H6N6). H5N6 was first reported in domestic poultry in early 2014 from Laos, Vietnam, and China. Since then it has continued to be widely reported from domestic flocks in these countries (primarily China).

In April 2014, the first case of a human infected with the H5N6 influenza virus was reported from Sichuan Province in China. Since then, seven additional human cases have been reported, all from China. The most recent case was reported from Jieyang, Guangdong Province a few days ago. Of these eight cases, six have been reported by the World Health Organization (see links below).

Based on onset dates two of these cases occurred in 2014, four in 2015. Onset dates for the two most recent cases have not yet been reported. Among these cases are five males and three females. One of the females was pregnant. Her child was delivered by caesarian section and the woman is apparently still under treatment. Media reports indicate that the child was not infected.  Ages range from 25 to 50 years old. Five the eight have died according to media reports.


To date, there is no evidence of human-to-human transmission among these eight cases of H5N6. The fatality rate is high, but there are too few cases to project a fatality rate for a larger population of infected individuals. It is not known if subclinical cases of H5N6 are occurring. No asymptomatic cases have been reported and there are no reports of seroprevelance studies of H5N6 among humans.

As shown in the map below, these eight cases from the past two years are widely scattered over China. The map also depicts the location of reported H5N6 outbreaks in poultry flocks in southern China and northern Laos. Like the distribution of human cases, domestic flocks infected with H5N6 are widely scattered across a large area. The wide-spread geographic distribution of infected poultry along with the dispersed nature of human infections in this area suggests that more human cases are likely to be reported in the future. With such a large animal reservoir this influenza virus could reassort and become more easily transmitted to humans. Were H5N6 to pick up the ability to transit easily among humans, H5N6 could become a deadly pandemic virus. 

Citations for Human Cases of H5N6

H5N6 influenza virus infection, the newest influenza (case 1)

Human infection with a novel, highly pathogenic avian influenza A (H5N6) virus: Virological and clinical findings (case 2 and 3)

WHO Links (case 1) (case 2) (cases 3 and 4) (case 5) (case 6)

Other Selected H5N6 Citations