ANTIVIRALS FOR H1N1 INFECTION
Use of antiviral drugs against influenza A(H1N1)
21 May 2009
For what purposes can antiviral drugs be used against influenza A(H1N1)?
So far most people who have contracted the new A (H1N1) virus have experienced influenza-like symptoms (such as sore throat, cough, runny nose, fever, malaise, headache, joint/muscle pain) and recovered without antiviral treatment.
Antiviral drugs may reduce the symptoms and duration of illness, just as they do for seasonal influenza. They also may contribute to preventing severe disease and death. Influenza A (H1N1) is a new virus and only a small number of people with the infection have been treated for it with antiviral drugs. WHO is in touch with public health authorities and clinicians in affected countries and is gathering information about how effective the drugs are.
To which antiviral drugs does this influenza virus respond?
There are two classes of antiviral drugs for influenza: inhibitors of neuraminidase such as oseltamivir and zanamivir; and adamantanes, such as amantadine and rimantadine. Tests on viruses obtained from patients in Mexico and the United States have indicated that current new H1N1 viruses are sensitive to neuraminidase inhibitors, but that the viruses are resistant to the other class, the adamantanes.
Could the virus become resistant to oseltamivir and zanamivir?
Resistance can develop to antiviral drugs used for influenza. Therefore, WHO and its partners are monitoring antiviral drug resistance.
Under what circumstances should antiviral drugs be administered?
Antiviral drugs are to be used according to national pandemic influenza preparedness plans. Public health authorities in some countries have decided to treat patients likely to have this disease as a part of public health measures.
Where antiviral drugs are available for treatment, clinicians should make decisions based on assessment of the individual patient's risk. Risks versus benefits should also be evaluated on a case by case basis.
Should I take an antiviral now just in case I catch the new virus?
No. You should only take an antiviral, such as oseltamivir or zanamivir, if your health care provider advises you to do so. Individuals should not buy medicines to prevent or fight this new influenza without a prescription, and they should exercise caution in buying antivirals over the internet.Warning on purchase of antivirals without a prescription, including via the Internet [pdf 35kb]
What is WHO doing about getting antiviral drugs to countries as preparation for a pandemic?
WHO’s first priority is to provide an emergency stock of antiviral drugs to countries that have no or insufficient stock of the drugs and lack the capacity to procure these drugs themselves.
WHO is also working with Member States, donors and other groups that have stockpiles and are willing to share these with WHO for distribution to countries in need.
Which drug will be provided, and how much of it does WHO have available?
WHO had a global stockpile of approximately 5 million adult treatment courses of oseltamivir. Part of this stockpile has already been distributed through the WHO Regional Offices, which are handling allocation and distribution. WHO is currently distributing the remaining 3 million adult treatment courses of this stockpile to developing countries in need.
WHO continues to assess needs and to work with manufacturers to secure more donations of antivirals. More antiviral drugs will be distributed once these donations are received.
Which countries will receive the drug, and how will they be selected?
WHO has arranged the first deployment of antiviral drugs from the WHO stockpile to 72 countries. Priority was given to vulnerable countries, taking into consideration national manufacturing and procurement capacity. As necessary, other countries will be supported through regional office stockpiles.
What if the initial emergency deployment turns out to be inadequate?
WHO is in discussion with manufacturers regarding the potential need for scaling up production. It is WHO's understanding that manufacturers have plans for producing large numbers of treatments quickly.
WHO will work on behalf of its Member States to secure further antivirals as needed, either through donations or purchase at the lowest possible price.