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influenza
36
NOV / DEC 2013
I
Healthcare Journal of NEW ORLEANS
likely as those over 65 to get sick with this
virus, according to the CDC.
Second, the 1918 flu likely originated in
a Kansas farming community, where pigs,
birds, and humans lived in close prox-
imity, that was located near a large army
base. The base, Camp Funston, housed over
50,000 troops, and people regularly trav-
eled between the rural community and the
base, exposing a farm-origin virus to a large,
crowded population. The new virus was then
able to not only spread through this large,
tightly packed population of soldiers, but
was also regularly exported out as troops
moved to different army bases in the U.S.
and were deployed to Europe. This ‘perfect
storm’ scenario is not likely to be repeated
in the contemporary developed world. With
today’s communication and public health
systems in place, an outbreak this severe, in
circumstances like these, would be noticed
and acted upon much earlier.
Third, the conditions of war most certainly
had a large impact on the evolution of the
virus. Normal, peacetime conditions favor
the evolution of mild viruses, since people
with severe illness tend to stay home, and
therefore isolated, whereas those with mild
illness tend to go to work or elsewhere where
they mingle with, and infect, other people.
Therefore, viruses causing mild illness have
a selective advantage over those that cause
severe illness. Under wartime conditions,
however, those with mild illness will tend
to stay outside, whereas those with severe
illness will be crowded together in field hos-
pitals, ideal places for the spread of influ-
enza. Conditions in contemporary Louisi-
ana therefore favor mild strains of influenza.
On the other hand, virulent strains might
be selected for in regions of the world cur-
rently experiencing war or upheaval. The
speed of modern transportation and gen-
eral mobility of the global population make
it entirely possible that such strains could
then be transported far and wide. After all,
it was not the war itself, but simply cargo
ships arriving from afar that brought the
1918 influenza epidemic to NewOrleans that
long-ago, ill-fated September.
n
flu virus and a wild-bird avian influenza
virus (AIV) contracted during hunting (or
biological collection) activities. While anti-
body evidence clearly shows that hunters
do get infected with AIV, the authors con-
cluded that, due to the fact that seasonal
human influenza and AIV are active at dif-
ferent times of the year here, it is unlikely
that such recombination would occur. How-
ever, the season of peak activity of the H1N1-
2009 virus in Louisiana did coincide with
that of AIV in wild birds, making reassort-
ment between these two strains possible
in unvaccinated hunters or ornithologists.
So, if flu viruses are constantly develop-
ing new strains via reassortment, is it just
a matter of time before a severe pandemic
like the 1918 flu sweeps through the world
again? A few epidemiological clues provide
hints of the likelihood of such an outbreak.
First, whereas the seasonal flu is more severe
in vulnerable patients with weaker immune
systems, the 1918 flu preferentially affected
healthy individuals with strong immune sys-
tems; half of the victims were in their 20s and
30s. (Research done with reconstructed 1918
influenza virus supports an over-reaction
by the immune system itself as the cause of
most of the fatalities.) A pattern of human-
to-human transmission preferentially affect-
ing healthy individuals with robust immune
systems would serve as a stark warning sign.
This is not the pattern seen for H7N9 and
H3N2v. For the H1N1-2009 pandemic, how-
ever, this was somewhat true; individuals
aged 24 and younger were 15 to 20 times as
r
...in states like Louisiana, the popularity
of waterfowl hunting may present
another source of new influenza strains—
direct infection of hunters with wild-
bird viruses. Louisiana hosts the largest
harvest of wild birds in the USA.