TUESDAY, Sept. 8 (HealthDay News) — Antiviral medications such as Tamiflu and Relenza, which are effective in treating the H1N1 swine flu, should be taken only by people hospitalized with the flu or those at high risk for complications from the disease, U.S. health officials said Tuesday.

Those at risk include people with underlying health conditions, such as asthma or diabetes, as well as the very young, the elderly, and pregnant women, officials said.

Because the H1N1 swine flu remains mild for the vast majority of people who get it, most people won’t need these medications at all, according to new guidelines for antiviral drug use issued by the U.S. Centers for Disease Control and Prevention.

“Antiviral medicines are a critical part of our tool kit in countering influenza, both the 2009 H1N1 influenza virus and seasonal flu strains,” Dr. Anne Schuchat, director of CDC’s National Center for Immunization and Respiratory Diseases, said during an afternoon news conference.

But, Schuchat added, “most children, adolescents and adults who have influenza-like illness do not need antiviral medicine.”

One reason why: If too many people take antiviral medicines it could increase the risk that the virus would become resistant to these drugs, Schuchat said.

“We have seen a bit of antiviral resistance already with the 2009 H1N1 strain, and we hope this won’t take off,” she said. “A critical feature is to use these antivirals very carefully so they can have benefit and not lead to problems.”

Because most people who get the flu — whether H1N1 swine flu or seasonal flu — will not be tested to see what type of flu they have, the new guidelines are based on symptoms, not a particular flu strain, Schuchat said.

“A key point of the antiviral guidance is that hospitalized patients who are suspected to have influenza need prompt treatment with antiviral medicines,” she said. “That can be a very important way to reduce the severity of illness. We don’t want providers to wait until test results are available, but we want them to start antivirals when you suspect influenza.”

The new guidelines also recommend that, when high-risk people have been in contact with someone who has the H1N1 swine flu, doctors should wait to see if flu symptoms develop before starting treatment with antivirals.

“Instead of starting antivirals, we give providers an option we call ‘watchful waiting,’ and wait and see if fever develops,” Schuchat said. “And, when fever or respiratory problems develop, give antivirals then.”

Another key to the best use of antivirals in people at risk for complications is to start the drugs as soon as flu symptoms appear, Schuchat said.

She stressed, however, that the new guidelines leave room for judgment and discretion on the part of doctors. “Every patient is different, and we want clinicians to have that opportunity to customize care for each patient,” she said.

The recommendations include:

• Treatment with antivirals is recommended for people at higher risk for complications. These include children younger than 5 years old, adults 65 and older, pregnant women, people with chronic medical or immunosuppressive conditions, such as patients on chemotherapy, and people younger than 19 years of age who are receiving long-term aspirin therapy.
  
• Treatment should not wait for lab tests because testing can delay treatment and a negative rapid test for flu does not rule out influenza.
  
• For some high-risk patients, doctors may choose to give them antiviral prescriptions that can be filled should symptoms appear.

Schuchat noted that cases of H1N1 swine flu — now the predominant flu strain in the United States — have already started to increase, especially in southeastern states. “The H1N1 flu never went away this summer,” she said. “It is not surprising that we are seeing this uptick in cases.”

The good news is that the H1N1 virus still hasn’t mutated into a more dangerous form, which means that the vaccine currently being tested should be a good match, she said.

The first 45 million doses of the vaccine are expected by mid-October.