Pregnant women and the extremely obese are among those at high risk for complications from the influenza or flu -- including death -- and should be tested and begin antiviral treatment promptly, according to new guidelines.

The new guidelines released by the Infectious Diseases Society of America (IDSA), noted that antiviral treatment should be given within two days after the start of flu symptoms in people both at high risk for complications (such as bronchitis, middle ear infection, and pneumonia), and even for those without.

"High-risk individuals who are hospitalised with flu complications are at an increased risk for serious bacterial infections and infectious diseases. Physicians' expertise is critical to ensuring they receive the best care," said Andrew T. Pavia, from the University of Utah in the US. 

"Annual influenza vaccination is the best way to prevent influenza, but it is not 100 per cent effective. Those at high risk need to be encouraged to seek medical care right away if they develop influenza symptoms during influenza season," added Timothy M. Uyeki, chief medical officer of the National Center for Immunisation and Respiratory Diseases in the US.

Influenza testing is important because physicians are more likely to treat patients with antiviral medications if they have a definitive diagnosis, further reducing the likelihood of prescribing antibiotics inappropriately, especially in outpatients. In addition, newer and highly accurate molecular tests that deliver results in 15-60 minutes should be used instead of rapid-influenza diagnostic tests (RIDTs), which produce quick results, the guidelines said. 

However, it can prove to be falsely negative in at least 30 per cent of outpatients with influenza. Others in the high-risk category include young children (especially those younger than two years old), women who have recently given birth, those with a weakened immune system due to disease or medication (such as people with HIV or AIDS, cancer, who have had an organ transplant or who are on chronic steroids), as described in the journal Clinical Infectious Diseases. Typical flu signs and symptoms include fever, cough, muscle aches, chills, runny nose and sore throat. Other symptoms can include headache and chest pain.