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Monday, September 2, 2013

What is the MERS virus ?

What is the MERS virus and what do Bats have to do with it?

The MERS virus (Middle East Respiratory Syndrome) has been on the news a lot. Recently, a virus fragment was isolated in a bat, captured in the same area as the first diagnosed patient, in Saudi Arabia. Read this summary to learn more about this story.

MERS Virus and the Bat out of Hell

Last week there was news reports that the virus responsible for the Middle Eastern Respiratory Syndrome (MERS) was found in a bat in Saudi Arabia. As per usual the headlines pounced on this story announcing that bats were definitely the source of the MERS virus. I want to write a quick post going over the basics of what we know of MERS, and where the bats come into the picture.

✤ MERS belongs to a type of virus known as coronaviruses. They are RNA viruses, meaning their genome is made of RNA; in contrast, ours is made of DNA. Coronoviruses are so named because under an electron microscope they appear circular with spikes sticking out of the surface, much like the solar corona of our Sun. 

✤ The most famous coronavirus is the virus responsible for SARS (Severe Acute Respiratory Syndrome). The new MERS virus is not the same as the SARS virus, but there is concern because it is related to bat coronaviruses, and could therefore spread rapidly among humans.

✤ Since being discovered last year, MERS has 108 laboratory-confirmed cases of infection, including 50 deaths.Understanding the origins and possible reservoir (long term host) of MERS can help us control its spread within the region. 

✤ So where did MERS come from? Scientists went to the home of the first known MERS patient in Saudi Arabia (who died last year) and collected samples from 96 bats that were captured close to where the man lived and worked. By sequencing the genetic material isolated from these samples, the scientists found  *a piece of viral RNA identical to that of the virus isolated from the patient who died*. Of all 96 bats that were analyzed, they only got one hit from a single bat's fecal pellet. The findings were reported in the journal Emerging Infectious Diseases and is #OpenAccess( 

✤ Before we rush off to proclaim that bats are definitively the source of the MERS virus, it is worth noting that the scientists only isolated a single fragment of the viral RNA. From a single batNo infectious MERS coronavirus has been isolated from a bat yet. Clearly, more animals need to be tested, more samples need to be sequenced before jumping the gun. Meanwhile, MERS is a virus to keep a close eye on.

✤ As an aside, apparently the scientists were hoping to isolate more genetic material from the samples, but US Customs 'helpfully' thawed all the samples! "The samples, collected in October 2012, were frozen and transported to Columbia University on dry ice. But customs officers opened the shipment and its contents sat at room temperature for 2 days, thawing all the samples".  Geniuses.

Further reading:
☣ A good article (albeit behind a silly paywall) in Science about why bats seem to be such common hosts for various viruses that infect us (

☣ Excellent write-ups from +Vincent Racaniello  on his Virology blog about this emerging virus ( and

☣ Latest WHO update on MERS August 30th 2013 (

☣ Results from sequencing the genetic material of 96 bats from Saudi Arabia published in Emerging Infectious Diseases#OpenAccess ( 

Image: Transmission electron micrograph of MERS coronavirus particles, colorized in yellow
Image and the National Institute of Allergy and Infectious Diseases.