Biology Reference
In-Depth Information
2
The Virulence of Poverty
Our worst nightmare may not be a new one. 25
Richard Webby and Robert Webster
Influenza is both familiar and unknown. Although easily distinguished from most common colds by a char-
acteristic moderate to high fever and dry cough, influenza A can exhibit an extremely broad range of symp-
toms (including sore throat, headache, bone aches, conjunctivitis, dizziness, vomiting, and diarrhea) that
overlap with numerous other so-called “grippes, catarrhs and colds.” The continuing, rampant prescription
of antibiotics for influenza is proof of the difficulty that most general practitioners and clinic staff face in
distinguishing between viral and bacterial infections. “[I]t is now accepted,” writes one world authority,
“that influenza is quite protean in its manifestations. Influenza cannot be distinguished readily on clinical
grounds from other acute respiratory infections, and during virologically confirmed outbreaks of influenza
the proportion of influenzal illnesses confirmed by laboratory tests as being influenza is currently about
half.” 26
If diagnosis is often mere guesswork, an accurate census of influenza mortality is almost an impossibil-
ity: except during pandemics, influenza is usually only the accessory to murder. By destroying the ciliated
epithelial cells that sweep dust and germs out of the respiratory tract, flu encourages superinfection by bac-
teria. ( Haemophilus influenzae —widely believed in 1918-19 to be the actual pathogen of the pandemic—is
a famous fellow traveler.) A lethal synergy is believed to operate between influenza A and pneumonic bac-
teria, with Staphylococcus aureus and Strepto coccus pneumoniae being particularly vicious; thus, bacteri-
al pneumonia is the most common, or at least the most clearly associated cause of influenza deaths. But
how to distinguish influenza-related cases from the rest of pneumonia mortality? As Registrar General of
England William Farr first realized during an influenza epidemic in 1847, the infection's well-defined sea-
sonality (October to March in the Northern Hemisphere) in temperate countries allows a rough calculation
of excess mortality by simple subtraction of the annual average from the winter spike. 27
Although epidemiologists now use sophisticated regression modeling, influenza mortality is still estim-
ated in North America and Europe as excess annual mortality. Recently, however, it has become evident
that the traditional reporting category “pneumonia and influenza” shortchanges influenza's deadly impact.
Most of the winter spike in ischemic heart disease, diabetes, and cerebrovascular disease mortality may
also result from the impact of the annual flu epidemic; conversely, “influenza vaccination has been associ-
ated with large reductions in the risks of primary cardiac arrest, recurrent myocardial infection, cardiac dis-
ease and stroke.” 28 In a normal year, researchers now believe that influenza kills between 36,000 to 50,000
mostly elderly (and especially poor) Americans, a reality that belies the benign image of flu as nothing
more than a winter nuisance. 29 Sadly, an infection that primarily kills infants and old people is not likely to
arouse as much concern as a disease that kills young or middle-aged adults.
 
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