As the A/H1N1 flu virus continues to spread, the World Health Organization (WHO) has indicated recently that it's possible to finally raise the pandemic alert level to phase 6, which means a world-wide influenza pandemic is under way.

What exactly is a pandemic? How wide and hard will it infect people? Can the world cope with it? To answer these questions, people need to have a clear vision of the real meaning of this flu epidemic to avoid unnecessary panic.

Not the end of the world

Flu pandemic sounds terrifying as it once claimed many lives, especially the notorious "Spanish flu" in 1918, which caused astonishing 40 to 50 million deaths worldwide.

Normally a flu pandemic is caused by a newly-emerged or not-known-by-human virus. Due to human body's lack of immunity to this new virus and the lag of vaccine production, many people can be easily infected and even die from complications.

However, the severity of flu pandemics is different. The two flu epidemics in 1957 and 1968 exerted far less severe impact on the world, and caused much fewer deaths.

WHO experts and officials have repeatedly pointed out that a pandemic by definition mainly refers to the geographic spread of the disease, instead of the severity of consequences.

Take the A/H1N1 flu for example, if the WHO formally declares a pandemic by raising its alert level to six, it just means that the virus has caused sustained human-to-human transmission in regions outside North America, such as Europe or Asia. It has nothing to do with severity or mortality of the epidemic, which are still evolving and nobody can actually predict for the moment.

"Phase 6 does not mean, in any way, that we are facing the end of the world," WHO Director-General Margaret Chan has said.

"It is important to make this clear because otherwise...it will cause an unnecessary panic," she told Spanish newspaper El Pais in a recently published interview.

Take it seriously

Though unnecessary panic should be avoided, the world cannot afford to take a possible pandemic lightly. After all, pandemics like the one in 1918 once caused terrible consequences.

Recently the A/H1N1 epidemic in Mexico, the epicenter of the current outbreak, has shown signs of decline, and the country's overall number of confirmed deaths reported to the WHO stands at only 29 as of Wednesday. But WHO officials are continuing to warn countries to keep high alert as the disease is still spreading to more countries and flu viruses are notorious for their unpredictable behavior.

"In this situation, it's critical that we continue to maintain and strengthen our alertness and surveillance," Dr Keiji Fukuda, WHO director for health security and environment, told a news briefing in Geneva.

He expressed particular concern that the disease is traveling to the southern hemisphere, where colder months are coming and flu virus tends to be more active.

WHO chief Dr Margaret Chan also stressed the importance of keeping high alert for the new virus.

"At this point, we have no indication that we are facing a situation similar to that seen in 1918," she told the UN General Assembly on Monday. "But this situation can change, not because we are overestimating or underestimating the situation, but simply because influenza viruses are constantly changing in unpredictable ways," she warned.

Learning lessons from history

History has shown that when a new epidemic appears, it can threaten a large number of countries in many different ways, simply because the world is interconnected at many different levels. And today's world is even more integrated than ever. But just as Dr. Fukuda pointed out: "The same things which make diseases a threat are also things which allow us to control them."

Fukuda said the international community has learned important lessons from tackling SARS and other diseases in recent years.

"When the world was able to put up resources together, to work together in a coordinated effort, it was really able to contain an outbreak which could have spun out of control," he said.

According to WHO chief Margaret Chan, the current world is actually better prepared for an influenza pandemic than at any time in history.

"Preparedness measures undertaken because of the threat from H5N1 avian influenza were an investment, and we are now benefiting from this investment," she said.

Dr Fukuda echoed Chan's remarks. "I do want to emphasize at this point in history, this is the best surveillance we ever had. We are able to see a situation unfold in a way we've never been able to do in history before. This is a new phenomenon, this has been impossible 20, 30 or 50 years ago," he said.

The A/H1N1 virus is still spreading. Nobody knows exactly how the situation will evolve. But with high alert on the pandemic, close cooperation among countries, and the "best surveillance" in hand, the world can certainly minimize the harm of this new virus.