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1918 influenza evolution

bhjelle at unm.edu bhjelle at unm.edu
Wed Mar 22 10:31:40 EST 1995

In article <Pine.SOL.3.91.950321170508.15087A-100000 at corona>,
Patrick O'Neil  <patrick at corona> wrote:
>>Again, I don't understand the firm connection in your mind between
>>transmissability and virulence. These concepts should be dissociated.
>>Does a dying soldier transmit influenza virus more effectively than one
>>who is destined to survive?
>In this circumstance, the sick soldier is not going to be isolated from
>the other soldiers to prevent spread and allow recovery.  The unfortunate
>soldiers, therefore, easily transmit virus to fellow soldiers who will
>also not be isolated.  Since so many hosts are so easily available and

>virus to neighbors who will easily pass it on to others, etc.  In this
>case, the fastest, most virulent variants have the upper hand over low
>virulence variants, unlike normally, and even as they quickly lay up the
>host, the host is still effective in passing virus on to new host.  That
>is why I tie the two concepts together in this circumstance:  easy
>transmissibility and selection in favor of high virulence.  Under normal

I think I'm a little closer to understanding your point now,
thanks. Given enough soldiers in the trenches for awhile, it
may be possible that there could be selection for viruses
that replicate quickly. However, lots of viruses replicate quickly
and have little virulence (ie, very low case-fatality). So,
your use of phrases like "...fastest, most virulent variants...",
which takes it as a given that those two properties are
tightly linked is still bothersome. To my mind, given that
influenza is spread by the respiratory route and through
fomites, and that such transmission would be markedly reduced
when a victim dies, it still remains far from clear that
virulence *per se* is favored in settings such as the above.


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