Pandemic (H1N1) 2009 is a new virus that has not circulated among humans before. This virus is different from previous or current human seasonal influenza viruses.

The virus is transmitted by inhaling infected droplets expelled by coughing or sneezing or by touching contaminated hands or surfaces, the same as the normal seasonal flu.

To prevent spread, people should cover their mouth and nose when coughing or sneezing, stay home when they are unwell, clean their hands regularly, and avoid crowded areas where possible.

The symptoms of Pandemic (H1N1) 2009 are similar to seasonal influenza, such as fever, cough, headache, muscle and joint pain, sore throat and runny nose, and sometimes vomiting and diarrhoea.

Pandemic (H1N1) 2009 is continuing to spread rapidly across the Western Pacific Region (WPR). The spread of the virus to all countries, worldwide, is considered inevitable.

The increasing number of countries reporting sustained community transmission means that many of them have moved from containment of the virus to mitigation of its impact on communities.

Public health measures have been useful in slowing the rate of transmission and helping to minimize the numbers of people sick at the same time, thus easing the strain on health services.

This pandemic is currently referred to as of “moderate” severity, with the overwhelming majority of patients recovering, even without medical treatment, within a week of the onset of symptoms.

However, the virus has also caused severe illness and deaths. It is important to note that there are groups considered to be at “higher risk” of serious complications from Pandemic (H1N1) 2009.

People with existing cardiovascular disease, respiratory disease, diabetes and cancer are currently considered at higher risk of serious complications from the new flu virus. Asthma and other forms of respiratory disease have been consistently reported as underlying conditions associated with an augmented risk of severe pandemic disease in several countries.

There is evidence that pregnant women are at higher risk for more severe disease – especially those in the second and third trimester. A recent report suggests obesity may be another risk factor for severe disease.

These groups should seek medical advice if they develop influenza like symptoms.

Countries without reported cases should continue to make their efforts to detect initial cases and respond to them rapidly. However, for countries where community level transmissions are occurring, the counting of all individual cases is not considered possible and essential in such countries. This shift has been recommended by WHO, because as the pandemic progresses, monitoring trends in disease activity can be done better by following trends in illness cases rather than trying to test all ill persons, which can severely stress national resources. It remains a top priority to determine which groups of people are at highest risk of serious disease so that steps to protect them can be taken.

For the latest Western Pacific Region update (WHO/WPRO)

For all Western Pacific H1N1 updates (Media Centre - Archive)

Where to get more information

During public health emergencies, it is important to seek accurate information about the situation. For official information on this evolving situation and for technical and communication guidance for health administrators, health professionals and the general public, please click on the following links:

World Health Organization

US Centers for Disease Control & Prevention

France – Institut de Veille Sanitaire