Chances of catching flu down to first strain caught

A study published in the journal Science, has indicated that a person’s chance of becoming ill from a new strain of flu are partly determined by the first strain they were ever exposed to.

The research analysed 18 strains of influenza A and the hemagglutinin protein attached.

The scientists explained that there are only two forms of the hemagglutinin protein and people develop an immunity to the type that their body meets first. They claimed the findings could also provide some explanation as to why some flu outbreaks cause more deaths and serious
illnesses in younger people.

The study classed the two types of hemagglutinin as ‘blue’ and ‘orange’ and explained that people born before the late 1960s had been exposed to the ‘blue’ H1 and H2 hemagglutinin so were less at risk of falling ill again from the same type protein later in life. However their risk of falling ill and potentially dying from the ‘orange’ form of influenza was increased and vice-versa.

Dr Worobey, who led the research, said the finding could explain the unusual effect of the 1918 ‘Spanish flu’ pandemic, which was more deadly among young adults.

"Those young adults were killed by an H1 virus and from blood analysed many decades later there is a pretty strong indication that those individuals had been exposed to a mismatched H3 as children and were therefore not protected against H1.

"The fact that we are seeing exactly the same pattern with current H5N1 and H7N9 cases suggests that the same fundamental processes may govern both the historic 1918 pandemic and today's contenders for the next big flu pandemic."

Jonathan Ball, professor of molecular virology at the University of Nottingham, said: "This is a really neat piece of work and provides a reason why human populations have been susceptible to different strains of bird influenza over the past 100 years or so.

"The findings are based on analysis of patient records and they certainly need validating in the laboratory, but nonetheless the results are pretty compelling."