were more likely than others to die of influenza (Noymer and Garenne, 2000). However, contradictory evidence from 120 autopsy reports of influenza victims showed that none had evidence of TB in the lungs, leading to the speculation that TB could have had a protective effect (Taubenberger, 2004).

Genetic features of the 1918 virus have also been examined for clues to its deadliness, but none of the mutations identified have been shown to correlate with virulence (see Taubenberger in Chapter 1). Such genomic studies are, however, revealing the genetic basis of viral adaptation to human infection and transmission. For example, research on the 1918 hemagglutinin gene and its product suggest that a single amino acid change allowed the avian-like virus to bind to a human receptor (Kobasa et al., 2004); it was speculated that a similar change in the avian H5 gene—now circulating among birds infected with pandemic H5N1 influenza—would make it easier for the avian virus to infect humans.

Applying Lessons Learned from Past Pandemics

There is particular pressure to recognize and heed the lessons of past pandemics in the shadow of the worrisome 2003–2004 flu season. At the time of this report’s release, 44 confirmed human cases of H5N1 avian influenza occurred in Thailand and Vietnam; 32 (72 percent) of these patients, mostly children and young adults, have died of the disease (ProMED-mail, 2004a; WHO, 2004d). Six of those confirmed deaths have occurred in Vietnam during a resurgence of the avian flu epidemic since July 2004, as this report was being prepared (ProMED-mail, 2004b,c). Concurrently, Thailand has confirmed four deaths since July 2004 (ProMED-mail, 2004d,v), with one case possibly having been transmitted from daughter to mother (ProMED-mail, 2004e).14,15

In addition, an early-onset, severe form of influenza A (H3N2) made headlines when it claimed the lives of many children in the United States in late 2003. As a result, stronger than usual demand for annual flu vaccine outstripped the vaccine supply, of which 10 to 20 percent typically goes unused (Hosbach, 2004). Because statistics on pediatric flu deaths had not been collected previously, it is unknown if the 2003–2004 season witnessed a significant change in mortality patterns. However, in response to these deaths, the Centers for Disease Control and Prevention’s (CDC’s) Advisory


Editor’s note: During the production process, further evidence suggests the daughter transmitted H5N1 to her mother and this report also suggests she transmitted H5N1 to her aunt (Ungchusak et al., 2005).


Editor’s note: It should be noted that during the production process of this report there were 12 additional deaths in Vietnam during January 2005 and the first case and death in Cambodia, bringing the total number of deaths to 45 (ProMED-mail, 2005).

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