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Lifelong protection against severe influenza 
  
 The first influenza attack that a child suffers can affect the way that their lifelong immunity to the virus builds up. A wide range of influenza A virus subtypes infect humans. Subtype H5 belongs to HA group 1 (which also includes H1 and H2 subtypes), and subtype H7 belongs to HA group 2 (which also includes the H3 subtype). Gostic et al. found that birth-year cohorts that experienced first infections with seasonal H3 subtype viruses were less susceptible to the potentially fatal avian influenza H7N9 virus (see the Perspective by Viboud and Epstein). Conversely, older individuals who were exposed to H1 or H2 subtype viruses as youngsters were less susceptible to avian H5N1-bearing viruses. A mathematical model of the protective effect of this imprinting could potentially prove useful to predict the age distribution and severity of future pandemics. 
  
 Science, this issue p. 722; see also p. 706 ||||| THURSDAY, Nov. 10, 2016 -- The year you were born could help predict your risk of becoming seriously ill or dying after exposure to a flu virus that jumped from animals to humans, researchers suggest. 
  
 It was believed that previous exposure to a flu virus offered people little to no protection against new animal-origin flu viruses, according to investigators from the University of Arizona in Tucson and the University of California, Los Angeles. 
  
 But an analysis of all known cases of severe illness or death caused by the H5N1 and H7N9 bird flu viruses showed that the first infection with flu virus as child helps determine which new bird flu viruses people would be protected against in the future. 
  
 Depending on when people were born, they were infected with different types of flu viruses for the first time as children, the researchers explained. This causes their bodies to produce different types of flu-fighting antibodies. 
  
 As an analogy, "let's say you were first exposed to a human 'orange lollipop' flu as a kid," said co-senior author Michael Worobey. "If later in life you encounter another subtype of flu virus, one from a bird . . . that your immune system has never seen before but whose proteins also are of a similar 'orange' flavor, your chances of dying are quite low because of cross-protection," he said. Worobey is head of the department of ecology and evolutionary biology at the University of Arizona. 
  
 "But if you were first infected with a virus from the 'blue lollipop' group as a kid, that won't protect you against this novel, 'orange' strain," he explained in a university news release. 
  
 If you do get infected with a strain you had as a child, the researchers estimated that there is a 75 percent protection rate against severe disease, and an 80 percent protection rate from flu death. 
  
 The findings could lead to new ways to reduce the risks of major flu outbreaks. The next step is to determine exactly how a child's first bout of the flu affects the immune system and possible ways to modify it with a vaccine, the researchers said. 
  
 "In a way it's a good-news, bad-news story. It's good news in the sense that we can now see the factor that really explains a big part of the story: Your first infection sets you up for either success or failure in a huge way, even against 'novel' flu strains," Worobey said. 
  
 "The bad news is the very same imprinting that provides such great protection may be difficult to alter with vaccines: A good universal vaccine should provide protection where you lack it most, but the epidemiological data suggest we may be locked into strong protection against just half of the family tree of flu strains," he added. 
  
 The study was published in the Nov. 11 issue of the journal Science. 
  
 The U.S. Centers for Disease Control and Prevention has more on the flu. 
  
 Copyright © 2016 HealthDay. All rights reserved. 
  
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 / Updated By Maggie Fox 
  
 People's birth years can affect their risk of catching certain strains of influenza — probably because their first case of flu somehow sets their immune system, researchers reported Thursday. 
  
 Their findings could be good news for what scientists predict about the risk of a killer flu pandemic, and they could also help researchers find better flu vaccines, the researchers said. 
  
 A new study explains why children and young adults are more likely to be infected with H5N1, shown here, while H7N9 disproportionately affects older adults. CYNTHIA GOLDSMITH / UCLA 
  
 “Our work implies that we have never seen a true ‘virgin soil’ influenza pandemic,” the team wrote in their report, published in the journal Science. “Virgin soil” means a population that has no immunity at all to a new infection. 
  
 The teams were looking at the puzzling characteristics of two strains of bird flu that keep popping up in people: the H5N1 and H7N9 avian influenza viruses. 
  
 They’ve been spilling over into people for years and scaring scientists who see the potential for a pandemic of flu that could kill tens or even hundreds of millions of people. But this hasn't happened yet. 
  
 And, oddly, while H5N1 has hit young people and children especially hard, H7N9 seems to attack older people. 
  
 “Roughly half of the people are quite well-protected against one of these potential pandemic viruses but not the other." 
  
 H5N1 has infected 856 people since 2003 and killed 452 of them, WHO reports. H7N9 has infected 452 people and killed 124 of them, according to the Center for Infectious Disease Research and Policy at the University of Minnesota. 
  
 The team at the University of Arizona and the University of California Los Angeles dove into the numbers, examining the reports of each case, who was affected and how severely. 
  
 Related: Where has H5N1 Been, Anyway? 
  
 They found an almost startling link with birth year. 
  
 “It’s ridiculously predictive,” said Michael Worobey, an expert in viral genetics at the University of Arizona. 
  
 Worobey thinks he knows why. Other research suggests that early infections “imprint” the body’s immune system. It makes sense — the human immune system makes cells and antibodies that “learn” to recognize and react more quickly to microbial invaders the next time they infect someone. 
  
 Worobey has also found that influenza viruses that commonly infect people can be categorized into two groups. Group 1 consists of subtypes H1, H2, and avian H5, while group 2 includes seasonal H3 and avian H7. 
  
 Related: What's in a Flu Name? 
  
 Influenza A viruses all are named for two proteins found on their surfaces: hemagglutinin (the H in a flu name) and neuraminidase (the N in a flu name). Thus flu strains get names such as H5N1 or H1N1 or H3N2. So human H1N1, H2N2 and the H5N1 bird flu virus are all related in Group 1, while the H3N2 seasonal flu virus is related to the H7N9 bird flu strain. 
  
 Every few decades, the predominant flu strain changes. So the H1N1 flu strain that killed tens of millions of people in 1918 hung around infecting people until 1957, when a pandemic of H2N2 flu swept the world and took over. Then H2N2 predominated until 1968, when the H3N2 “Hong Kong” flu took over. 
  
 Most recently, the H1N1 “swine flu” caused a minor pandemic in 2009. Now H1N1 and H3N2 both regularly circulate as seasonal flu viruses. 
  
 What Worobey and colleagues found was that people born in 1968 and later are less likely to be made severely ill by H7N9. They believe this is because the first flu strain that would have infected them would have been H3N2, which is in the same group as H7N9. 
  
 Related: Canadian Woman Infected With H7N9 Flu 
  
 And people born before 1968 are less likely to die or be made severely ill by H5N1, because their first flu infection would have been an H1N1 or H2N2 strain. 
  
 “Roughly half of the people are quite well-protected against one of these potential pandemic viruses but not the other,” Worobey said. 
  
 "Our findings show clearly that this 'childhood imprinting' gives strong protection against severe infection or death from two major strains of avian influenza," added James Lloyd-Smith, a UCLA professor of evolutionary biology who worked on the study. "These results will help us quantify the risk of particular emerging influenza viruses sparking a major outbreak." 
  
 “This is really the first evidence out in the real world that this kind of cross-protection is possible." 
  
 “It’s imprinting. Not the virus, not the behavior of people, but being exposed to different viruses at an early age,” Worobey said. 
  
 Flu strains mutate all the time, which is why people need a fresh flu shot every year. But Worobey and other researchers say there are unchanging, or “conserved” parts of the flu virus on the “stem” of the mushroom-shaped hemagglutinin structure that the human immune system can recognize. 
  
 It obviously does not provide perfect protection, but enough to protect most people with this immune imprinting from the most severe disease, he said. 
  
 “It is an extra barrier that is probably protecting us from even more frequent influenza pandemics,” he said. 
  
 More importantly, later flu infections do not seem to alter this mechanism, although this theory needs testing. 
  
 The researchers cannot say whether regular flu vaccination affects this “imprinting” effect. People are now encouraged to get annual flu vaccines starting as infants, and they get a cocktail of vaccines that protect against both the Group 1 H1N1 and Group 2 H3N2 viruses. 
  
 They also cannot say whether peoples’ susceptibility to seasonal flu is affected by imprinting. Flu is so very common that it will be hard to say which virus first infected someone and then follow them through life to see which strains make them sicker. 
  
 But it might be possible to use the findings to make better vaccines, Worobey said. 
  
 “This is really the first evidence out in the real world that this kind of cross-protection is possible,” Worobey said. ||||| People born before 1968 are likely to be protected from a dangerous strain of bird flu, a study has indicated. 
  
 Until now, it was believed that previous exposure to a flu virus conferred little or no immunity against new influenza that can jump from animals into humans, such as the H5N1 strain that has infected hundreds of people in the Far East. 
  
 But research from the University of Arizona and the University of California suggests that the vast majority of people exposed to H1 or H2 strains of flu as children are largely protected against H5N1. 
  
 The H1 and H2 strains were prevalent until 1968, when the strain H3 became widespread. People born after that date were found to have greater immunity to the H7N9 strain, which has also killed people in China. 
  
 Researchers say it explains why certain age groups are often more vulnerable in pandemics. 
  
 “We're not a completely blank slate when it comes to how susceptible we are to these emerging flu viruses,” said Dr Michael Worobey, head of the University of Arizona’s Department of Ecology and Evolutionary Biology. 
  
 “Even if we've never been exposed to H5 or H7 viruses, we have some kick-ass protection against one or the other." |||||
Output:
Good news, people born before 1968! You're a whole lot less likely to die from the H5N1 strain of bird flu, the Telegraph reports. Bad news, people born before 1968! You're a whole lot more likely to die from the H7N9 strain of bird flu. In a study published Friday in Science, Dr. Michael Worobey says the year people were born is "ridiculously predictive" of how protected they are from different bird flu strains, according to NBC News. People born before 1968 likely were infected with the H1 or H2 flu strains as children because those strains were prominent at the time. People born after 1968 were likely infected by the H3 strain for the same reason. Researchers say whichever strain of flu people had first permanently affected their immune system going forward. Prior to this study, scientists didn't think this process of "immunological imprinting" affected susceptibility to flu strains with animal origins, UPI reports. That turns out not to be the case thanks to proteins shared by various flu strains. The study found that people have 75% protection against becoming seriously ill and 80% protection against dying from either H7N9 bird flu or H5N1 bird flu depending on the year of their birth. "We have some kick-ass protection against one or the other," Worobey tells the Telegraph. That could explain why strains of bird flu haven't become the millions-killing pandemics some experts predicted. H7N9 and H5N1 have infected a little more than 1,300 people total since 2003, killing fewer than 600 of them. (Our bodies fight off illness far better in the mornings.)