WHO likely to counsel restraint on antivirals for H1N1

May 12, 2009 (CIDRAP News) – The World Health Organization (WHO) plans to release clinical guidance that will say most patients sick with the novel H1N1 influenza (swine flu) will not need antiviral treatment, but the drugs should be considered for high-risk groups, a WHO official said today.

"Soon we will be publishing initial guidance for clinical management for this disease," said Dr. Nikki Shindo, leader of the WHO clinical team for response to the H1N1 epidemic, speaking at a news briefing. "We are highlighting the fact that most of the patients will not require hospitalization or antiviral therapy."

Later she added, "We will recommend to consider the use of antivirals for high-risk groups or the group of people at increased risk, depending on availability."

Yesterday the WHO said the new virus usually causes only a mild illness in otherwise healthy people.

As described by Shindo, the WHO guidance on antivirals will probably align with what the US Centers for Disease Control and Prevention (CDC) is recommending. The CDC's interim clinical guidance says that patients who have an uncomplicated febrile illness typically do not need antiviral treatment unless they are at risk for complications. High-risk groups are the same as those for seasonal flu:

  • Children under 5
  • Adults 65 and older
  • People with chronic medical conditions or immunosuppression
  • Pregnant women
  • Children and youth on long-time aspirin therapy
  • Nursing home residents

The CDC and WHO say the new virus is sensitive to oseltamivir and zanamivir (the neuraminidase inhibitors) but resistant to amantadine and rimantadine (the adamantanes).

Shindo emphasized that the use of antiviral treatment in any given country will be strongly influenced by the availability of the drugs and the country's pandemic preparedness plan.

"It largely depends on the availability of antivirals," she said. Later she commented, "We don't have a really strong position on the use of antivirals, because it's part of their national pandemic preparedness plan."

Shindo also commented that antivirals are being used much more extensively for H1N1 in Europe than in North America.

"European countries, which are mainly importing their cases, have been using antivirals very aggressively," she said. "Countries like Mexico and the United States are trying to save their treatment for patients with underlying conditions and also the other groups at increased risk, such as pregnant women."

At a CDC news briefing today, Dr. Anne Schuchat said, in response to a question about extensive antivral use in Europe, that the focus in the United States is on using antivirals for treatment of sick people, whereas some other countries are using antivirals to try to prevent the virus from spreading from infected travelers to others. Since geographic containment of the virus is no longer possible in the United States, the emphasis is on reducing its impact, she noted.

Shindo was asked if the aggressive use of antivirals in Europe might contribute to resistance to the drugs. She replied that the rise of osletamivir resistance in seasonal H1N1 viruses over the past 2 years seemed unrelated to use of the drug, as it arose in areas where oseltamivir was not often prescribed for seasonal flu.

Also, in some human H5N1 cases in Vietnam, the rise of oseltamivir resistance was ascribed to "suboptimal treatment doses," she said, adding, "So public health officials may decide to use antivirals aggressively because that's what they've been preparing for and that's part of their pandemic preparedness plan."

Shindo said the WHO has little information so far about the results of antiviral treatment in novel H1N1 cases and wants countries to communicate their findings. In particular, the agency has very little information about the effectiveness of late treatment with oseltamivir or about results with zanamivir. For both drugs, the manufacturers say treatment should be started within 48 hours after illness onset.

Besides discussing antivirals, the WHO clinical guidance will recommend simple supportive treatment such as antipyretics and hydration, Shindo said.

See also:

WHO's novel H1N1 flu page

CDC guidance on antivirals
http://www.cdc.gov/h1n1flu/recommendations.htm

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