Lab Matters Winter 2018 - Page 7

feature Coffin Supply is Exhausted Undertakers Must Wait Turn for Caskets to Bury “Flu” Victims Headline, The Courier-Journal, Louisville October 23, 1918 “I thought I was going to die. I remember lying here in the front room and watching hearse after hearse pass by my window outside.” So Barbara Burkett-Halapin, PhD, remembers her grandmother telling her as she recounted her illness with the influenza virus that ravaged the world in 1918-19. Burkett-Halapin’s grandmother, whose experience is captured in the US Centers for Disease Control and Prevention’s (CDC’s) Pandemic Influenza Storybook, was lucky. She survived the virus at age 20 in small-town Shenandoah, VA. But an estimated 675,000 Americans— and 50 million to 100 million people worldwide—succumbed to the first pandemic influenza of the 20th Century, 100 years ago this year. The toll of that pandemic—described as the “greatest medical holocaust in history”—was so great that it eclipsed the loss of 18 million lives in World War I and actually decreased the population of the US. Because the “grippe,” as influenza was also known, disproportionately killed those in the prime of life, it shortened US life expectancy by 12 years. After the virus slowed in 1919, this particular lineage disappeared into the pig population—a known virus reservoir, considered a “universal mixing bowl” where avian, swine and human flu viruses reshuffle their genomes. Then, nearly a century after its deadly debut, a descendent of the 1918 virus re-emerged to prompt the first pandemic of the 21st Century—the 2009 influenza A(H1N1) pandemic. But this time the virus was substantially changed. And so was the world. PublicHealthLabs @APHL 100 Years of Detective Work In 1918, no one even knew for sure that influenza was a viral disease; the potentially grave respiratory illness was widely believed to be bacterial, perhaps caused by a species of Bacillus. But then, the field of public health laboratory practice was still in its infancy. In 1930, scientists isolated influenza virus for the very first time, from a specimen taken from a pig. This classical swine flu strain was later dubbed influenza A(H1N1), with the “H” and the “N” referring to hemagglutinin and neuraminidase, two glycoproteins that sit on the surface of the virus and play a major role in its transmission and pathogenicity. (Hemagglutinin, additionally, is the major antigenic target that triggers the host’s immune response.) In 1933, the first human influenza virus was isolated. With laboratory case confirmation now possible, the public health community made rapid gains. A second influenza genus, influenza B, was identified in 1940. Not long thereafter, the first vaccines appeared. Today, the world enjoys a robust, laboratory-based Global Influenza Surveillance and Response System (GISRS), coordinated by the World Health Organization (WHO), which was itself established in 1948. Yet, the threat of another 1918- type pandemic persists. “I wouldn’t call it likely, but I wouldn’t be at all surprised if it happened,” said Pete Shult, PhD, who heads the Communicable Disease Division of the Wisconsin State Laboratory of Hygiene. “We have it in the back of our mind that it could happen at any time. That’s a prudent way to look at it.” Said Daniel Jernigan, MD, MPH, director of CDC’s Influenza Division, “Influen za is as much of a foe now as it was [in 1918]. We can treat it better, we can prevent it better, we can detect it a lot better. But the potential for a severe pandemic now is just as great as it was then.” The most worrisome emerging influenza today is the A(H7N9) virus, first detected in China in 2013. H7N9 is the only virus rated as having a “moderate-high” risk for emergence and impact based on the criteria considered in CDC’s Influenza Risk Assessment Tool, including (1) viral properties (e.g., antiviral susceptibility), (2) population attributes (e.g., existing immunity) and (3) viral ecology (e.g., infection rates in animals). To fully appreciate the risk, it helps to recall the impact of past pandemics. The 2009 A(H1N1) virus infected 24% of the world population and had a case fatality rate about 0.02%—a relatively mild outcome compared with its 1918 ancestor, which infected a third of the global population and killed over 2.5% of those stricken. In contrast, influenza A(H7N9) has a mortality rate approaching 40%. Although human H7N9 cases have been mostly associated with exposure to infected poultry, the number and geographic distribution of cases expanded significantly between the first four Chinese outbreaks—involving 798 human infections during March 2013 to September 30, 2016—and the fifth outbreak—involving 759 human infections during October 1, 2016 to August 7, 2017. Should the virus acquire greater facility for human-to-human transmission, GISRS will face its biggest test yet. Winter 2018 LAB MATTERS 5