Pandemic Planning » General Flu Information

General Flu Information

Why is Avian Flu a concern?

In February 2004, avian influenza virus (H5N1) was detected in birds in Vietnam and in October 2005 cases were identified in Turkey. Cases so far are recognized to have been transmitted from bird to human and the current WHO phase of pandemic alert is level 3, described as "no or very limited human-to-human transmission. Spread by migratory birds and seen as especially virulent because it can be transmitted from birds to mammals to humans, and because it continues to evolve, avian H5N1 virus represents a significant threat to human health.

The concern is that the virus will change into a form that is highly infectious for humans and spreads easily from person to person. Such a change could mark the start of a global outbreak (a pandemic).

How is Avian Flu spread? 

H5N1 infections in humans are caused by bird to human transmission of the virus by inhalation of infectious droplets, by direct (and perhaps indirect) contact.  Human-to-human transmission of the H5N1 virus has been reported within household clusters and findings suggest that the virus strain may be adapting to humans.

The incubation period of the H5N1 virus is generally between 2 to 15 days with initial, or early, symptoms that include high fever, lower respiratory tract symptoms, diarrhea, vomiting, abdominal pain and possible bleeding from the nose and gums. 

See WHO Confirmed Human Cases of Avian Influenza H5N1 

Can it be treated?

There is currently no commercially available vaccine to protect humans against H5N1 virus, though government organizations are developing pre-pandemic vaccines based on current lethal strains of H5N1, collaborating with industry to increase vaccine production capacity, and seeking ways to expand or extend the existing supply of antiviral medications commonly used for influenza.

Studies done in laboratories suggest that some of the prescription medicines approved in the United States for human influenza viruses should work in treating avian influenza infection in humans. However, influenza viruses can become resistant to these drugs, so these medications may not always work. Additional studies are needed to demonstrate the effectiveness of these medicines.

The H5N1 virus that has caused human illness and death in Asia is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza. Two other antiviral medications, oseltamavir and zanamavir, would probably work to treat influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.

For more information about H5N1 drug and vaccine development, see

Flu Facts

The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccination each year. Some people, such as older people, young children, and people with certain health conditions, are at high risk for serious flu complications. Learn more by downloading our Flu Facts Sheet. 

PDF: Flu Facts Sheet

Introduction to Avian Influenza

The following PDF provides information on symptoms, and causes of avian influenza, as well as risk factors and how to best prevent catching avian flu.

PDF: Introduction to Avian Flu

Avian Flu: Frequently Asked Questions

The following PDF provides background information about avian influenza, including recent outbreaks, the viruses, and the risk to human health.

PDF: Avian Influenza FAQ

Travelers' Questions About Influenza

The following PDF provides information about influenza for travelers, including

PDF: Travelers' FAQ

Dictionary & Terms Defined

PDF: Pandemic Glossary Terms