Changes in a key protein of the influenza virus can help predict the severity of outbreak, and even how long people remain infectious, according to a University of Georgia researcher.
The amount of pre-existing immunity across the population also plays a role and could help explain the unusual impact of the novel influenza A H1N1 virus in younger people.
In a paper published today in the journal Science, an international team led by Andrew W. Park looked at a model for flu transmission and the virus' ability to mutate in order to escape the host's immune system.
Change as small as a two amino acid difference between the circulating virus and the virus from a past immunization or infection can raise the risk of infection.
That in turn influences how many in the overall population are infected, with greater difference producing greater outbreaks, said Dr. Park, an assistant professor in the Odum School of Ecology and in the College of Veterinary Medicine.
The ability to produce those changes becomes an adaptation that helps the virus escape the immune system of those with some level of pre-existing protection.
"Like many of these RNA viruses it is routinely making errors as it replicates so it is spinning off these mutants all the time and that's clearly part of its life history," Dr. Park said.
The study was done with equine influenza virus so he cautioned about trying to apply the findings broadly.
But the study also conversely showed that a mismatch between virus strains could be somewhat minimized by increasing the number vaccinated.
"We know that influenza can change fairly rapidly and we know that sometimes vaccines take a little while to manufacture and dispatch," Dr. Park said.
"It's trading off between the quality, in terms of the genetic closeness, and the quantity that's required in terms of the number of people vaccinated, which was a quite interesting result," he said.
The findings fit in well with earlier work by Jackie Katz, of the Centers for Disease Control and Prevention, on the 2009 H1N1 virus that found cross-reactive proteins in many people born before 1950 and little in those born after 1980, suggesting that older people had some protection from being exposed to a similar flu strain.
It could help explain why younger people seem hardest hit by the new virus but it causes relatively little illness in the elderly, who are normally among the most vulnerable to flu.
Moving from thinking about individual immunity to the immunity of people as a whole is how some are now reordering their thinking about flu, Dr. Park said.
"Starting to think about immunity at the population level is a really important step forward," he said.
Reach Tom Corwin at (706) 823-3213 or tom.corwin@augustachronicle.com.
VACCINE SHOTS ON WAY
Shots against the novel influenza A H1N1 virus could soon be available in health departments in the Augusta area. Shipments of the injectable form of the vaccine should be coming in the next couple of days, said Melba McNorrill, child health and immunization coordinator for the East Central Health District.
"It's still just trickling in," she said.
Columbia County Health Department is expecting 1,300 shots "hopefully by Monday," said Nurse Manager Linda Graves.
No one could provide an answer about Richmond County Health Department on Thursday.
The shots are important because they can be given to many more people in the priority group than the nasal mist formulation, which can only be given to healthy people ages 2 to 49. Among those in the priority group are pregnant women, those six months to 24 years old, health care workers, adults ages 25 to 64 with a chronic disease such as asthma and caregivers for infants six months and younger.
There were 24.8 million doses of the vaccine against the new virus produced by Thursday, 1.6 million more doses than the day before, said Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention.
Those numbers and the progress of the pandemic will be updated by CDC today. Vaccine is being shipped out as quickly as it can be produced, but Dr. Schuchat acknowledged frustration with those who can't find it. Production has been slower in part because this particular strain does not grow well in eggs, which are traditionally used in influenza vaccine production, she said.
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One theroy on why the young are hit hard is that they began taking regular flu shots a few years ago, have taken lots of antibiotics, lots of other vaccinations, eat lots of sugar, almost all are low in vit D and have ended up with a weak immune system. Their bodies have not been allowed to fight off anything and they have become very weak. We need to study the children not getting the flu to see what is the difference. NAET continues to be used to successfully fix those with the flu.
soldout - You have this EXACTLY backwards. The reason that young folks with healthy immune systems are having more significant problems with H1N1 is due to the severity of their immune reaction to the virus. That is what is contributing to the development of severe respiratory problems. It's bad enough that you offer a daily dose of this lunatic witch-doctor crap, but when it's totally wrong, it's even worse and more dangerous.
That is why it is called a "theory" and is from medical sources. Time will prove it wrong or right. All approaches like NAET, EFT, reflexology and others will either succeed or fail with the test of time. God gave us very strong bodies and when they fail there is a reason. Finding the reason something breaks is always better than fixing something that is broken. God wants us healthy and said the curse without a cause will not come which tells me to always look for a reason. One local doctor encouraged his patients to never, never have their child sleeping in a room without a window cracked open whether winter or summer. He thought the indoor pollution was creating breathing and ear problems. That was his theory years before anyone was talking about indoor air pollution. Nothing wrong with discussing ideas or theories.