As deadly as ever, avian flu proves a persistent foe

Even as avian flu has faded from the headlines, the lethal viral illness continues to strike in certain corners of the world and, in an especially ominous development, health authorities said they believe it has reemerged in Vietnam, where control measures had stopped its spread for more than a year.

So far this year, at least 44 people have contracted the disease, mainly in Indonesia and Egypt, and the virus has proved as deadly as ever: Three of every five people contracting avian flu this year have died.

For more than four years, disease trackers have monitored the movement of avian flu -- in both birds and people -- from Asia to the Middle East and then into Africa and the edge of Europe. Its ability to kill with such frequency ignited fears that the virus, known by scientists as H5N1 , could spark a global flu epidemic capable of claiming millions of lives.

In most cases, health authorities have determined that the human victims of the virus contracted it directly from infected birds, usually poultry kept in homes or at workplaces. And while there is no indication that the virus has acquired the ability to spread easily human-to-human, disease specialists said its persistent presence is evidence that it remains a threat that cannot be ignored. "This stuff is still out there, growing in animals," said Dr. David Ozonoff , a Boston University School of Public Health professor who runs an online flu encyclopedia. "It's sort of like a big witch's brew. It's bubbling away -- will it boil over?"

The H5N1 virus now causing trouble was identified in Hong Kong in 1997 and then vanished -- at least among humans -- until 2003, when three people in Vietnam and one in China contracted the disease. They all died. In the next three years, 259 more people fell ill from avian flu; 154 of them died.

In 2004 and 2005, Vietnam was the epicenter of avian flu activity, accounting for more than half of all the world's cases each year.

Aided by specialists from the World Health Organization and the United States, the Vietnamese government moved aggressively to contain the outbreak. Poultry flocks by the millions were culled and replacement flocks were vaccinated against the germ. At the same time, Vietnamese health authorities established elaborate networks to make sure they detected every human case.

But the disease is tough to contain.

"The thing is," said Gregory Hartl , a WHO spokesman, "there continue to be outbreaks in unvaccinated ducks and geese."

Earlier this year, reports from Vietnam indicated that avian flu had been detected in waterfowl in at least four provinces. And then, last week, Vietnamese health authorities reported that a 30-year-old man in a Hanoi hospital had tested positive for the disease; further tests are being performed to confirm that diagnosis. Authorities said that several days before falling ill, the man had slaughtered chickens for a wedding banquet.

Dr. Joe Bresee , a flu specialist with the US Centers for Disease Control and Prevention , said that the re appearance of avian flu in Vietnam is a cautionary lesson about the challenges of stopping the virus.

"Vietnam has done a great job, but with the virus present in countries around them, it's a very difficult virus to keep out," Bresee said. "Viruses are very small, and they can get across borders in many different ways. It speaks to the fact this is not a country problem -- it is really a global problem."

And animal-borne viruses can spread for commercial reasons, too.

"Infectious diseases very often tend to be, unfortunately, very good markers of undocumented trade in animals," said Stephen Morse , an epidemiologist at Columbia University's Mailman School of Public Health . Disease specialists have warned that avian flu is more likely to be carried into the United States by the black market trade in animals than to arrive via migratory birds.

Political wrangling has also, at times, threatened the global cooperation that has helped keep the disease contained. For five months, Indonesia stopped providing WHO with samples of the virus needed for vaccine development research, fearing it could not afford any shots created. But last week, that dispute was resolved.

Disease specialists are concerned, too, that some nations may not be reporting all their cases of bird flu.

In the countries hit hardest by the virus, health agencies already overwhelmed by the need to provide basic medical services are finding it difficult to maintain the surveillance systems necessary to track the disease.

"We're clearly getting a sense that there's fatigue after several years of reporting this disease," said Michael Osterholm , director of the Center for Infectious Disease Research & Policy at the University of Minnesota. "I'm very concerned."

There is fatigue in the United States, too.

In Massachusetts, for example, the Legislature has still taken no action on a February 2006 proposal by then-Governor Mitt Romney to spend $36.5 million on additional hospital beds, breathing machines, and medicines. The proposal has been reintroduced, but not voted on.

"People act like, if the pandemic hasn't happened by the end of the week, hey, it's not going to happen," Osterholm said. "This is not a discretionary activity. One day we will be held accountable for what we did or didn't do."

Stephen Smith can be reached at stsmith@globe.com.