11:00 Dose of EIDology: MERS, the Newfangled SARS

MERS and SARS, the Mean-Spirited Cousins of a Common Cold Virus

Perhaps you've heard of a disease called MERS ('Middle Eastern Respiratory Syndrome') in the last year or so.   This is especially prescient since it just took two more lives this morning.   MERS is severe viral pneumonia, and has a case fatality rate of about 30%.  The virus that causes it, MERS-CoV, first appeared in humans in 2012 in Saudi Arabia.  Since then cases have been reported in numerous countries (including the US), though most patients have had recent travel to the Mid East or a household contact who has.  This is because MERS does not appear to spread easily from person-to-person, and those who have it have almost exclusively become infected by contact with camels or dromedaries.

SARS ('Severe Acute Respiratory Syndrome') though...SARS was scary.  SARS was a disease worthy of the recent Ebola hysteria.  SARS had a 10% case-fatality rate, and was extremely contagious by droplet aerosol.  SARS emerged in humans in 2002 in Guangdong China following contact between humans and civet cats.  Within weeks, it has spread to other continents and a major satellite outbreak occurred in Toronto.  SARS took months to come under control under the auspices of some of the best healthcare and epidemiological care in the world.  

Ballet Students in China During the SARS Outbreak

Are these new viruses?  Not really, no.  They are both part of a family called Coronaviruses, which have long been recognized as minor pathogens of humans.  They are one of the major causative agents of the common cold.  Why are MERS-CoV and SARS Co-V so much more deadly?  It has to do with an idea called host adaptation (check back at 5:00!).  A question to consider as a preview: Does a good pathogen kill its host?