Bird Flu a 'Truly Nasty Virus'

PHOTO: About 500,000 people cross the border between Mainland China and Hong Kong every day.

HONG KONG -- A new strain of bird flu has been reported in China, and it has sickened 63 people and killed 14.

I spoke with my former colleagues at the Centers for Disease Control and Prevention, who are some of the world's leading experts on influenza. This new strain worries them for several reasons.

One fear is that this virus, called H7N9, will spread further, affecting more people in China and beyond.

Another fear is that the virus will mutate and develop the ability to spread easily from person to person.

They've already seen adaptations in this virus that make it suitable to humans: It can attach to cell receptors in our respiratory tracts and grow at our body temperature. Another concern is that unlike previous strains of bird flu, this strain doesn't seem to harm birds. It can spread among flocks silently, making tracking its movement quite difficult. It's a truly nasty virus.

That is why I headed for China: to see what was being done to understand and control an outbreak caused by a virus with real potential for harm.

It's been four years since the outbreak of the H1N1 virus, more commonly known as swine flu. At the start of that pandemic, I was serving as the acting director of the CDC. I remember the uncertainty in those early days, the sense that something quite dangerous was happening, something unstoppable.

In the years leading up to the outbreak, we had been keeping our eyes on a different flu virus -- a strain of bird flu called H5N1. Normally, influenza viruses infect only one species: bird viruses infect birds; human viruses infect humans; and so on. When viruses jump species you have to watch out, because the virus might learn to spread from person to person in a population that doesn't have immunity, causing a pandemic.

H5N1 bird flu had been around for several years, killing birds and many people who worked closely with birds. There was concern that a pandemic caused by that strain would be devastating -- bringing higher death rates than any strain of flu ever seen. Given that the H1N1 pandemic of 1918 killed as many as 40 million people, we were very concerned.

We developed response plans, stockpiled medications and conducted pandemic preparedness exercises. We wanted to be ready so that we could respond quickly and minimize the impact on people's lives. Thankfully, the virus never learned how to spread from person to person.

It was a humbling experience in 2009 when a new pandemic strain appeared seemingly out of nowhere. At the time it was identified, it had already filled hospitals in Mexico and had started to spread across the United States. That experience hasn't lessened my feeling that there is real value in paying very close attention any time an influenza virus crosses species. Those crossover events can signal the potential for flu pandemics. And if they're identified early, then theoretically we may be able to prepare lifesaving vaccines and implement measures to curb the spread.

But it's tough to predict which viruses will make the jump, and that brings us to where we are today: a new strain of bird flu in China, with new reports every day of its spread, and more severe disease in people.

Wednesday I'll catch you up with some of the methods they're deploying in Hong Kong, just in case this is a cross-species flu that mutates enough to spread through humans.

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