Last year, for the first time since avian flu emerged as a global threat, the number of human cases was down from the year before.

As the illness receded, the scary headlines — with their warnings of a pandemic that could kill 150 million people — all but vanished.

But avian flu has not gone away. Nor has it become less lethal or less widespread in birds. Experts argue that preparations against it have to continue, even if the virus' failure to mutate into a pandemic strain has given the world more breathing room.

There were 86 confirmed human cases last year compared with 115 in 2006, according to the World Health Organization, and 59 deaths compared with 79. Experts assume that the real numbers are several times larger, because many cases are missed, but that is still a far cry from a pandemic.

Dr. David Nabarro, the senior U.N. coordinator for human and avian flu, recently conceded that he worried somewhat less than he did three years ago. "Not because I think the threat has changed," he quickly added, but because the response to it has gotten so much better."

The world is clearly more prepared. Vaccines have been developed. Stockpiles of Tamiflu and masks have grown. Many countries, cities, companies and schools have written pandemic plans. The European Center for Disease Prevention and Control, created in Stockholm in 2005, just estimated that the European Union needed "another two to three years of hard work and investment" to be ready for a pandemic, but that is improving because previous estimates were for five years.

In the worst-hit countries — all poor — laboratories have become faster at flu tests. Government veterinarians now move more quickly to cull infected chickens. Hospitals have wards for suspect patients, and epidemiologists trace contacts and treat all with Tamiflu — a tactic meant to encircle and snuff outbreaks before the virus can adapt itself to humans.

Bernard Vallat, director general of the World Organization for Animal Health, recently called the virus "extremely stable" and, thus, less likely to mutate into a pandemic form. Many prominent virologists would vehemently disagree. But others who argued three years ago that H5N1 would not "go pandemic" are feeling a bit smug.

Dr. Paul A. Offit, a vaccine specialist at Children's Hospital in Philadelphia, was one of those who, he jokes, "dared to be stupid" by bucking the alarmist trend in 2005.

"H5 viruses have been around for 100 years and never caused a pandemic and probably never will," he said.

But Offit said he backed all preparedness efforts because he expected another pandemic from an H1, H2 or H3, the subtypes responsible for six previous epidemics, including the catastrophic one in 1918.