Australian scientists have discovered that a person's genetic makeup can influence how they are affected by illness - they say a certain genetic vulnerability can amplify an illness.
The researchers from the University of New South Wales have found people with a genetic vulnerability spend twice as long in bed when they become ill and are significantly more likely to have an intense illness during the acute stage of an infection - when fever, aches and pain first strike signalling the start of the body's immune response.
According to the researchers 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 but other people have a gene combination which makes them particularly hardy, with a less severe illness.
The research is the first to explore how genetic makeup determines the severity of an illness and could lead to ways in which people who are particularly vulnerable are identified and to the provision of individualised prevention and treatment programmes for common infectious diseases.
The researchers say in some cases it may even save lives as in the event of a major pandemic such as SARS or bird flu, where this vulnerable population might be given preference when a vaccine becomes available.
Lead author of the study Dr Ute Vollmer-Conna says it is widely acknowledged that individuals differ a great deal in their acute sickness response to an infection and an understanding of the important role genetic combinations play is now beginning to emerge.
Dr Vollmer-Conna from UNSW's School of Psychiatry, is an expert on how the brain and immune system interact and she says 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 due to their genetic make-up.
Dr Vollmer-Conna says this group in the population were found to spend twice as many days in bed during the acute illness and they also reported more than twice as many days when they were unable to function normally.
The research - the Dubbo Infection Outcomes Study - focused on a group of 300 people of a similar age and ethnic background who were enrolled after being diagnosed with acute glandular fever, Ross River virus or Q fever infections in the NSW town of Dubbo - of the 300, almost 28% (83 people) had the genetic predisposition to having a more severe and prolonged illness.
The researchers say their findings suggest that genetic variations underpin the severity of the response to acute sickness and also affect the recovery time.
The research is published in the current issue of the journal Clinical Infectious Diseases.