Age groups of 10-29 were worst affected during the 2009 swine flu epidemic say Swedish researchers.

Toomas Timpka and colleagues studied how five types of different influenza epidemics struck in Östergötland County of East Sweden between 2005 and 2010. Age seemed to be a factor responsible for the attack of flu. As an example the researchers say that with swine flu, 2.3 cases per thousand inhabitants were diagnosed in the 10-19 age group compared to only 0.2 cases per thousand 70 and older age group.

The risk of falling ill, in all flu outbreaks, was greater for the age groups of 30-39 while it was least for age group 70 and above. The study does not validate the existing belief that children are responsible in spreading flu. Regular vaccination of the elderly is said to have reduced their risks of a flu-attack.

However, Timpka says, it’s clear that the risk of being infected by flu is equally great in various age groups and he wants to study theories as to why:

“Our hypothesis is that the first influenza infection you get in your life affects your immune system. This means that your immune system learns to react to one category of influenza, but has a poorer defense against other types. This is one of the theories that we want to study.”

The body prepares antibodies in response to an external threat. Antibodies fight against an infection and remain in the body. Thus the body is incapable of fighting an infection for the first time. For immediate response to a threat, the body has T cells that can be released immediately to destroy the external agent

“Very small children have their mother’s antibodies. The most vulnerable group is children between one and three; they still lack their antibodies. As a rule they develop them in some form later”.

With the help of unique ABIS register (Alla Barn i Sydöstra Sverige, All Children in South-east Sweden), Timpka and his colleagues want to study which antibodies against various types of influenza were found in children. In ABIS, there are blood tests from most of the children born in the region between October 1997 and October 1999, a total of 17,000 children. The researchers want to follow a selection of these children up to the age of 16 that is through 2015 at the latest. They hope to see the first results in 2013.

“Today we know very little about the immunity in children against influenza and flu-like illnesses. This is knowledge that’s necessary, especially to better plan future vaccination programs,” Timpka says.

The study is published in PLoS ONE dated February 23,2012

What is flu?

Centers for Disease Control and Prevention (CDC) says, that influenza or flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times lead to death.

Swine flu or H1NI emerged between March and early April of 2009 in Mexico and U.S. By the month of May, the virus had spread to nearly 30 countries primarily due to human-human interaction. The alarming spread triggered a state of emergency and the World Health Organization raised its pandemic alert level to 5. (highest pandemic alert rate is 6)

Flu report 2012 in U.S

During week 13 (March 25-31, 2012), influenza activity was elevated in some areas of U.S, but declined nationally and in most regions.

To know more about 2011-2012 season, visit;

For the complete research article, See;