MERS: Deadly Virus from the Middle East Spreading Quickly

nCoV-1 Cynthia Goldsmith Maureen Metcalfe Azaibi Tamin

The MERS Middle East Respiratory Syndrome virus has an extremely high fatality rate. Photo by: Cynthia Goldsmith Maureen Metcalfe Azaibi Tamin

A lethal virus has emerged from the Arabian Peninsula and it’s striking fear in the hearts of public health officials throughout the world.

Middle East Respiratory Syndrome (MERS) virus materialized out of nowhere last summer, and has since infected at least 60 individuals -mostly in the Middle East.  Though this sounds like a relatively small number, apparently 65% of those infected die, and the virus appears to rapidly spread from person to person with minimal contact.  World Health Organization Director-General Dr. Margareth Chan recently stated this is an immediate threat to the entire world.

Another Coronavirus

Like severe acute respiratory syndrome (SARS), MERS is novel member of the coronavirus family.  These are large RNA viruses consisting of a spike-lined outer membrane (envelope) and an inner armored shell (protein capsid) that houses instructions for the virus.  The name comes from the spiked, crown-like appearance of these virions under the electron microscope. We find corona viruses throughout all mammals; they generally impact the upper respiratory tract. Besides SARS and MERS, several tamer members of this group are known to cause flu-like symptoms in humans.

Signs of MERS Infection

MERS has a long incubation period – it may simmer up to 2 weeks, with symptoms usually occurring within 10 days of transmission.  Signs and symptoms start out mild (cough, fever, and malaise) then progress over days to renal disease and pneumonia. So far more men have been infected, but all age groups are susceptible. Those with underlying medical conditions are at even more risk for severe illness.

MERS vs. SARS

Both SARS and MERS are novel emerging coronaviruses with high rates of person-to-person transmission.  SARS emerged from Southern China in November of 2002, and became a global threat by March 2003.  Of the 8,100 that became sick, 8% progressed to pneumonia and died. By 2004 the outbreak was over and no new cases were reported. The source of SARS appears to be the consumption of wild civet cats in China.

Of those with a diagnosis of MERS, thus far, 60% have progressed to pneumonia and renal problems before death. Researchers still do not know the source of MERS, but this novel coronavirus appears to be related to virus species that infect bats.

Click to Read Page Two: Why is MERS So Deadly and Contagious?

Could Rousettus aegyptiacus, the Egyptian fruit bat, be the source of MERS? Photo by Dawson

Could Rousettus aegyptiacus, the Egyptian fruit bat, be the source of MERS? Photo by Dawson

Why is MERS so Deadly and Contagious?

The ideal virus is usually well-behaved and tailored to a specific species.  These virions tend to lurk quietly in cells and are kept in check by the host’s immune system.  They silently evade with minimal negative impact to their host.  Their survival and spread depends on the host living a long and productive life, which allows frequent opportunity for interaction with others.

Sometimes an event occurs in the environment that brings two species in contact that normally don’t interact.  These accidental encounters allow for the opportunity to exchange novel microbes like bacteria and virions between the species.

Since the newly infected hosts has never encountered these microbes, it may have no immune defense against them. In this case, expect devastating illness. Eventually the virus may evolve in those that survive to get along with the host -achieving a homeostatic equilibrium-with mild or complete absence of symptoms.

MERS is Probably of Bat Origin

Another consideration is that virions are prone to mutations that might make it easier to take the leap between species.  This is probably the scenario with MERS. The MERS coronavirus appears to be quite similar to those that infect bats in regions of Africa and the Middle East.  Researchers hypothesize that bats harboring a new version of coronavirus are contaminating dates, which people produce and consume heavily throughout the Middle East. Bats may also transmit the virus to goats or camels, which then pass the virus to humans.

Middle East Respiratory Syndrome: Treatment Options

At this time there are few conventional options in the management of MERS beyond supportive measures and quarantine.  No antiviral medications or vaccines have been developed.  Emphasis is on prophylactic strategies like hand washing.

Resources
Assiri, A., A. McGeer, et al. Hospital Outbreak of Middle East Respiratory Syndrome Coronavirus. (2013). N Engl J Med. Accessed June 24, 2013.

Centers for Disease Control and Prevention USA. Middle East Respiratory Syndrome. (2013).

de Groot, R. J., S. C. Baker, et al. Middle East Respiratory Syndrome Coronavirus (MERS-CoV); Announcement of the Coronavirus Study Group. (2013). J Virol.

Drosten, C., M. Seilmaier, et al. Clinical features and virological analysis of a case of Middle East respiratory syndrome coronavirus infection. (2013).Lancet Infect Dis.

Memish, Z. A., A. I. Zumla, et al. Family Cluster of Middle East Respiratory Syndrome Coronavirus Infections. (2013). N Engl J Med.

Mou, H., V. S. Raj, et al. The receptor binding domain of the new MERS coronavirus maps to a 231-residue region in the spike protein that efficiently elicits neutralizing antibodies. (2013). J Virol.

Petherick, A. MERS-CoV: in search of answers. (2013). Lancet 381(9883): 2069.

World Health Organization: Global Alert and Response: Coronavirus Infections. (2013).

© Copyright 2013 James Pendleton, NMD, All rights Reserved. Written For: Decoded Science