Virus or bacteria? Using human genes to identify a fever’s cause

Gene expression signatures in blood can help distinguish between viral and bacterial causes of fever in young children. Shutterstock

Scientists have discovered a new way of distinguishing between childhood fevers caused by viral infections and those caused by bacteria, according to a new study published today.

The new finding paves the way for more targeted use of medication and will reduce the incidence of children taking antibiotics for viral infections, which are impervious to antibiotics.

However, one expert has said that a rapid bedside test could be years off.

The new findings, published in the Proceedings of the National Academy of Sciences (PNAS), centre on identifying the genetic expressions of viral infections and bacterial infections.

Traditionally, clinicians have tested white blood counts to offer clues as to the cause of childhood fevers but the new technique yields more accurate results.

The authors of the study analysed gene data from 30 feverish children who had various viral or bacterial infections and 35 children without fevers, some of whom were positive for viral infections.

The study revealed unique signatures for specific fever-causing viral infections such as herpes, adenovirus (which can cause respiratory diseases), or enterovirus (which can cause polio, hand foot and mouth disease and hepatitis A).

The researchers also identified genetic signatures for bacterial infections in febrile children.

“Our results support the paradigm of using host response to define the etiology (cause) of childhood infections. This approach could be an important supplement to highly sensitive tests that detect the presence of a possible pathogen but do not address its pathogenic (disease-causing) role in the patient being evaluated,” the researchers said in their paper.

Rapid bedside test

Trent Yarwood, an infectious diseases physician at Queensland Health and Associate Lecturer at the University of Queensland said the new study “aimed to differentiate viral infections by looking at the children’s immune response to the infection, rather than for the bacteria or virus itself or for antibodies - which usually come later in the infection.”

“Common bacterial tests rely on waiting for the bacteria to grow, while viral testing may not be helpful because there is a large number of different viruses that cause childhood illnesses and it’s not practical to test for all of them,” he said.

“Some different rapid tests are available, but they are better for confirming a suspicion, such as ‘Does this child have meningococcus?’ rather than ‘What is causing this child’s illness?’. They are also more expensive and not available quickly in all centres.”

Waiting three days for a test result for a serious bacterial infection like meningococcus means the patient may get seriously ill or die, he said.

A rapid test would be an ideal long-term goal, Dr Yarwood said.

“However, the technology is many years away from being able to be used by the bedside like this. Also, there are other advantages for more traditional testing. For example, this sort of test won’t give you information on the antibiotic sensitivity or resistance of a bacterial infection - or even what bacterial infection it is,” he said.