File photo taken shows that World Health Organisation (WHO) Director-General Margaret Chan of China addresses the 60th World Health Assembly at the United Nations headquarters in Geneva May 15, 2007. [Xinhua/Reuters Photo]

As the swine flu situation continues to get worse, the World Health Organization (WHO) on Wednesday raised the pandemic alert level to Phase 5, indicating that a full pandemic is imminent.

"I have decided to raise the level of influenza pandemic alert from Phase 4 to Phase 5," announced WHO Director-General Margaret Chan at a teleconference for the media late Wednesday, following close consultations with international experts.

"Influenza pandemics must be taken seriously precisely because of their capacity to spread rapidly to every country in the world," Chan said.

"Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short," according to a WHO explanation to its six-phase pandemic alert system.

Passengers wear protective masks at Mexico's city subway April 29, 2009. [Xinhua/Reuters Photo]

This was the second raise of the WHO's pandemic alert system in three days, indicating the quick worsening of the global swine flu situation. On Monday, the agency raised its alert level from Phase 3 to Phase 4.

"This change to a higher phase of alert is a signal to governments, to ministries of health and other ministries, to the pharmaceutical industry and the business community that certain actions should now be undertaken with increased urgency, and at an accelerated pace," Chan said in a statement.

"All countries should immediately activate their pandemic preparedness plans. Countries should remain on high alert for unusual outbreaks of influenza-like illness and severe pneumonia," she added.

A woman wears a mask while taking subway train in New York, the United States, April 29, 2009. [Xinhua Photo]

At this stage, effective and essential measures governments can take include heightened surveillance, early detection and treatment of cases, and infection control in all health facilities, according to the WHO chief.

Chan said the world today was actually better prepared for an influenza pandemic than at any time in history, due to preparedness measures already undertaken because of the threat from H5N1 avian influenza.

But she warned that "influenza viruses are notorious for their rapid mutation and unpredictable behavior. "

"The biggest question, right now, is this: how severe will the pandemic be, especially now at the start?" she said.

"It is possible that the full clinical spectrum of this disease goes from mild illness to severe disease. We need to continue to monitor the evolution of the situation to get the specific information and data we need to answer this question," she added.

(Xinhua News Agency April 30, 2009)