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H5N1 Bird Flu and 1918 Pandemic Flu Similarities

Recombinomics Commentary
February 18, 2005

>> Hien noted that influenza viruses in general were known to cause encephalitis and can damage the respiratory, nervous and digestive systems as well as the heart, kidney and liver.

"But we have not found encephalitis among the patients who died recently from bird flu in Vietnam," <<

Although this may be the first documented case of H5N1 associated with encephalitis, there have been prior examples in animals, as well as warnings about the varied presentations of pandemic influenza.

Proceedings of a recent workshop entitled The Threat of Pandemic Influenza: Are We Ready?, clearly detailed similarities between H5N1 and the 1918 pandemic influenza.

Neurological problems were seen then, and the pandemic generated interest in influenza research.  The first human influenza virus, WS/33, was isolated in 1933 and a variant that grew in mouse brains, WSN/33, was isolated in 1940.  Much of today's research, including using ferrets as an animal model, and using mice to determine lethality and tissue tropism, traces back to these experiments.

Recent data has shown that H5N1, like WSN/33, can grow in mice without adaptation, and some strains can be isolated from mouse brains.  Various strains can cause hind leg paralysis in mice and one of the 2004 isolates from Vietnam that is being used to create a pandemic vaccine causes hind leg paralysis in ferrets.  Moreover, chickens in Thailand with "nerve problems" and duck die offs in Vietnam with leg paralysis have been reported.

The failure to test out conditions for avian influenza has been a concern.   This concern is linked in part to comments on the 1918 flu pandemic described in the recent pandemic flu workshop summary:

Symptoms in 1918 were so unusual that initially influenza was misdiagnosed as dengue, as cholera, as typhoid.  Wrote one observer, "One of the most striking of the complications was hemorrhage from mucous membranes, especially from the nose, stomach, and intestine. Bleeding from the ears and petechial hemorrhages in the skin also occurred." A German investigator recorded "hemorrhages occurring in different parts of the interior of the eye" with great frequency. An American pathologist noted: "Fifty cases of soft subconjunctival hemorrhage were counted. Twelve had true hemotosis, bright red blood with no admixture of mucus. Three cases had hemorrhage". The New York City Health Department's chief pathologist said "Cases with pain look and act like cases of dengue...hemorrhage from nose or bronchi... paresis or paralysis of either cerebral or spinal origin... impairment of motion may be severe or mild, permanent or temporary... physical and mental depression. Intense and protracted prostration led to hysteria, melancholia, and insanity with suicidal intent."

The above comments combined with the recent cases in Vietnam that did not initially present with respiratory symptoms, clearly indicate that history is repeating itself. 

Although modern lab techniques allow for very specific sub-type testing of clinical samples and isolation of the etiological agent, the lack of surveillance remains scandalous.

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