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
. The research focused on five cytokine genetic variants. Cytokines are protein hormone messengers of the immune system which defend against infection.
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.
"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 perform their normal roles and duties."
The research focused on a group of 300 people of a similar age and ethnic background who were enrolled in the research after being diagnosed with acute glandular fever, Ross River virus or Q fever infections in Dubbo. The Dubbo Infection Outcomes Study is named after the NSW town in which the work was conducted.
Of those 300, almost 28 per cent (83 people) had the genetic predisposition to having a more severe and prolonged illness.
The co-authors on the paper are UNSW's Barbara Piraino, Barbara Cameron, Denis Wakefield and Andrew Lloyd from the Centre for Infection and Inflammation Research; and Tracey Davenport and Ian Hickie from the Brain and Mind Institute at the University of Sydney.