Immediate antiviral treatment is recommended for patients at high risk for complications from influenza, including pregnant women and the extremely obese, according to updated guidelines released by the Infectious Diseases Society of America (IDSA).

The guidelines, which are published in Clinical Infectious Diseases, pointed out that, while antiviral treatment is recommended within two days after the start of flu symptoms in those who aren't at high risk for complications, patients at high risk should be prescribed the drugs even if they have been sick for more than two days.

Flu antivirals. Source: Getty

In addition to pregnant women and people who are extremely obese, defined as a body mass index (BMI) of 40 or more, others in the high-risk category include:

• young children (especially those younger than 2 years old);

• women who have recently given birth;

• those with a weakened immune system due to disease or medication, including patients with HIV or AIDS, cancer, who have had an organ transplant or who are on chronic steroids;

• those younger than 19 years old who are receiving long-term aspirin therapy;

• patients with chronic medical conditions including asthma, neurological or neurodevelopmental disorders such as cerebral palsy, epilepsy and stroke;

• those with heart or lung disease, kidney, liver or metabolic disorders;

• nursing home residents; and

• American Indians and native Alaskans.

"Influenza can be serious, especially for the sizable group of people at high risk," explained Timothy M. Uyeki, MD, MPH, MPP, co-chair of the guidelines committee and chief medical officer of the Influenza Division of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention (CDC). "Annual influenza vaccination is the best way to prevent influenza, but it is not 100 percent effective. Those at high risk need to be encouraged to seek medical care right away if they develop influenza symptoms during influenza season."

At the same time, the guidelines urged that antiviral treatment should be started immediately in patients at high risk of flu complications who are being admitted to the hospital with suspected influenza, without waiting for the results of molecular influenza testing.

Guideline authors write that clinicians can consider antiviral treatment for adults and children who are not at high risk of influenza complications, with documented or suspected influenza, if they have illness onset 2 days or less before presentation, are household contacts of people who are at high risk of developing complications from influenza, particularly those who are severely immunocompromised, or if they are symptomatic healthcare providers who care for patients who are at high risk of developing complications from influenza.

In terms of using antivirals, the guidelines recommend that antiviral treatment be initiated as soon as possible with a single neuraminidase inhibitor (NAI) (either oral oseltamivir, inhaled zanamivir, or intravenous peramivir) and not use a combination of NAIs .

The document emphasizes that clinicians should not routinely use higher doses of Food and Drug Administration–approved NAI drugs for the treatment of seasonal influenza. A 5-day course of oral oseltamivir or inhaled zanamivir, or a single dose of intravenous peramivir is advise for uncomplicated influenza in otherwise healthy ambulatory patients.

Longer duration can be considered for patients with a documented or suspected immunocompromising condition or patients requiring hospitalization for severe lower respiratory tract disease (especially pneumonia or acute respiratory distress syndrome [ARDS]), because influenza viral replication is often protracted.

Clinicians are encouraged to investigate the possibility of bacterial coinfection in flu patients who present initially with severe disease – e.g., extensive pneumonia, respiratory failure, hypotension, and fever – and treat them empirically in addition to using antivirals.

That also is the case if patients deteriorate after initial improvement or fail to recover after 3-5 days of antiviral treatment, the guidelines state.