People with certain high risk gene combinations* are eight times more likely to suffer from a severe and prolonged illness when they have an infection, according to University of New South Wales (UNSW) researchers.
This group of people is significantly more likely to have an intense illness during the acute stage of an infection - when fever, aches and pain strike - to signal the start of the body's immune response.
Conversely, the researchers found some people had a gene combination which made them particularly hardy, with a less severe illness.
The findings have just been published in the prestigious journal Clinical Infectious Diseases.
This is the first time that the genetic determinants of severity of acute sickness have been explored.
Ultimately, it might be possible to identify people who are vulnerable and give them individualised prevention and treatment for common infectious diseases. In certain conditions, it may even be possible to save lives.
In the case of a major pandemic such as SARS or bird flu, this vulnerable population might be given preference with any vaccine that becomes available.
"It is widely acknowledged that individuals differ a great deal in their acute sickness response to an infection," said UNSW's Dr Ute Vollmer-Conna, the lead author of the paper. "We are starting to understand why and how genetic combinations play an important role.
"Some people will experience more severe symptoms than others when they are acutely sick with the same infection because their body's response is more intense which in turn is due to their genetic make-up," said Dr Vollmer-Conna, an expert in how the brain and immune system interact, from UNSW's School of Psychiatry.