Fearing that many countries would be ill prepared to deal with this potential threat, the World Health Organization in December urged all countries to develop or update their pandemic strategies. The UK government is currently revising its plans.

To date, 12 people have died of the infection in Thailand. But two people there who died of the infection apparently had no direct exposure to birds, suggesting they got the virus from another person, say researchers in an “early release” article in the New England Journal of Medicine (www.nejm.org, 24 Jan 2005). The cluster started with an 11 year old girl who played and slept near infected chickens. Although there have been other instances in which doctors suspected that bird flu had spread between humans, it was always hard to be sure if the victims had not just been exposed to the same source of the virus.

In this case, however, the evidence suggests that the 11 year old Thai girl transmitted the disease to her mother and aunt.

Doctors investigating the deaths talked to the girl's surviving family and healthcare workers. They also tested samples from the aunt and the dead mother and the girl. The mother, a garment worker, had not been around poultry. She was in the girl's house for only 10 minutes. The aunt had had no exposure to poultry for 17 days before falling ill. That is longer than the typical two to 10 days before symptoms usually appear after infection with this virus.

Neither the mother nor the aunt spread the disease to anyone else, an indication that the virus still cannot spread efficiently among humans, the researchers reported. Laboratory tests showed that the virus that infected the family had not mutated from its avian form, the researchers said.

“There is so much transmission going on between birds and humans [in Asia] that the likelihood of a genetic reassortment that would make the virus able to be transmitted in humans grows every day,” says Dr Michael Osterholm, an infectious disease epidemiologist at the University of Minnesota.

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Hundreds of thousands of squawking, migrating shorebirds descend on these beaches to gorge themselves on the protein- and fat-rich eggs. Over the course of a week, some of the birds will double their weight as they prepare to resume their journeys between South America and their summer breeding grounds in the Arctic. Up to 25 different species of birds stop here each spring.

It’s an ecological wonder not seen anywhere else in the world, and a bonanza for scientists who are looking to stop the next pandemic.

This year, their work has taken on new urgency as a dangerous flu virus, H5N1, tears through dairy cattle and poultry flocks in the United States. The world is watching to see if the threat will escalate.

McKenzie and Seiler are part of a National Institutes of Health-funded team at St. Jude Children’s Research Hospital that’s been coming to the beaches near here for almost 40 years to collect bird poop.

The project is the brainchild of Dr. Robert Webster, a New Zealand virologist who was the first to understand that flu viruses come from the guts of birds.

. . .“We were most amazed. Instead of in the respiratory tract, where we thought it was, it was replicating in the intestinal tract and they were pooping it out in the water and spreading it,” said Webster, who is now 92 and retired but still joins the collection trip when he can.

The poop, or guano, of infected birds is teeming with viruses. Out of all known influenza subtypes, all but two have been found in birds. The other two subtypes have only been found in bats.

On his first trip to the Delaware Bay in 1985, Webster and his team found that 20 percent of the bird poop samples they brought back with them contained influenza viruses. . .

The US is in the midst of one of those transitions now. A few months before the St. Jude team arrived in Cape May this year, H5N1 had turned up for the first time in dairy cattle in Texas.

The finding that H5N1 could infect cows put flu experts, including Webby, on alert. Type A influenza viruses like H5N1 had never before spread in cows.

Scientists have followed H5N1 for more than two decades. Some flu viruses cause no symptoms or only mild symptoms when they infect birds. These viruses are called low pathogenic avian influenzas, or LPAI. H5N1, which makes birds very ill, is called an HPAI, for highly pathogenic avian influenza.

It devastates flocks of farmed birds like chickens and turkeys. In the US, infected flocks are euthanized, or culled, as soon as the virus is identified, both to prevent the spread of the infection and to mitigate the birds’ suffering.

It’s not the first time US farmers have had to contend with a highly pathogenic bird flu. In 2014, birds migrating from Europe brought H5N8 viruses to North America. Aggressive culling, resulting in the deaths of more than 50 million birds, stopped that outbreak and the US remained free of highly pathogenic bird flu viruses for years.

The same strategy hasn’t stopped H5N1, however. H5N1 arrived in the US in late 2021, and despite aggressive depopulation of infected poultry flocks, has continued to spread. In the last two years, H5N1 viruses have also developed the ability to infect a growing variety of mammals such as cats, foxes, otters, and sea lions, bringing them a step closer to spreading easily in humans.

H5N1 viruses can infect humans, but these infections don’t travel from person to person so far because the cells in our nose, throat and lungs have slightly different receptors than the cells that line the lungs of birds.

It wouldn’t take much for that to change, however. A recent study in the journal Science found that a single key change to virus’ DNA would allow it to dock onto cells in the human lungs.

In the meantime, the virus was swirling all around them, popping up in herd after herd of cows in the Midwest and then California. Dozens of human infections in farmworkers had been reported, but the ones connected to dairy cattle had mostly been mild. No human-to-human transmission had been reported.

The cattle outbreaks seemed to slow briefly toward the end of the summer. Then came the serious human infections.

First, there was the teenager in Vancouver, Canada, hospitalized with respiratory distress. Then, more recently, a person in Louisiana became seriously ill with H5N1 after exposure to a backyard flock. In both instances, the virus was a slightly different type than the one circulating in cows. The virus identified in cows is from the B3.13 genotype, whereas the one found in both serious human infections is the D1.1 genotype, which has been circulating in wild birds and poultry, according to the US Centers for Disease Control and Prevention. There have been other cases of D1.1 infections in humans, too, in Washington state, in people who were assisting with a bird culling. Those cases were not as severe.