Coronavirus – Credit CDC PHIL
# 7532
If we know of one thing that viruses are particularly good at, it’s evolving over time. Viruses are continually changing – some more rapidly than others – but always with the same goal . . . survival.
Viruses need susceptible hosts in order to replicate. Since most viruses either leave behind a degree of immunity in (or kill off) their hosts, the need for new, immunologically naive hosts is ongoing.
So viruses must either change enough over time to be able to re-infect a host without triggering pre-existing antibodies, or they must find new hosts or species to infect.
Since viruses predate mankind by hundreds of millions of years (see Oldest Viruses Infected Insects 300 Million Years Ago), they’ve had a lot of practice evolving, and are exceedingly good at it.
Which is why we watch emerging viruses that infect mammals with such rapt attention. If today they do not possess the ability to spark a pandemic, there are no guarantees of what tomorrow will bring.
All of which serves as prelude to a NEJM editorial on the evolving picture of MERS-CoV. The authors point out that while a larger epidemic is far from a certainty, that this virus is not without pandemic potential.
Follow the link below to read their editorial in full, as there is much to glean here. I’ve only included a small excerpt.
Person-to-Person Spread of the MERS Coronavirus — An Evolving Picture
Stanley Perlman, M.D., Ph.D., and Paul B. McCray, Jr., M.D.
N Engl J Med 2013; 369:466-467August 1, 2013DOI: 10.1056/NEJMe1308724
(EXCERPT)
On one hand, coronaviruses are notorious for rapid adaptation to new hosts,8 a finding that is best illustrated by the ability of SARS-CoV to adapt to replication in the human lung. Adaptation involved changes in the surface glycoprotein, which is responsible for binding to the host-cell entry receptor, and in proteins involved in viral replication.9 Additional adaptation of MERS-CoV to human populations, although not observed thus far, is likely to occur and would augment the possibility of widespread infection.
Furthermore, the community (probably zoonotic) source for MERS-CoV remains unknown, making it difficult to know whether periodic reintroduction into human populations will occur and contribute to the potential for human adaptation. Moreover, the relative importance of aerosol transmission versus spread by large droplets or contact is unknown, but the mode of transmission will affect the likelihood of large-scale human infection.
Dr. Ian Mackay takes notice of this editorial this morning on his Virology Down Under blog as well. You can read his comments in:
Patients with diabetes or chronic renal failure at high risk for MERS...
