Bird Flu Has Infected Two Young People. Here’s Why Experts Are Concerned

New cases of bird flu in young adults raise concerns about virus mutation

Who Lauren J. Young

Ever since a strain of bird flu was detected in dairy cows in the US last spring, it has had an impact. relatively mild diseases in humansin most cases it has been observed in farm workers directly exposed to sick dairy cows or poultry. But two unusual cases involving children with no known prior contact with infected animals are raising scientists’ concerns that the infections portend a greater public health threat. A child with a mild infection in California on Tuesday gave a positive for low levels of the bird flu virus, which is probably H5N1. And Canadian health officials announced last week that a British Columbia teenager who was hospitalized with bird flu was there critical situation—the first local infection in the country.

“We’re not stopping the outbreak,” says Seema Lakdawala, associate professor of microbiology and immunology at Emory University School of Medicine. “This case in British Columbia will likely not be the only time a child is hospitalized with H5N1.”

In both cases, family members and close contacts have tested negative for the virus, and officials have reported no evidence of person-to-person transmission. The Canadian teenager, aside from his age and sex, initially had symptoms similar to other cases reported so far: fever, cough and conjunctivitis. eye infection common with bird flu. The teenager later developed acute respiratory distress, however, despite having no underlying health problems. A person from missouri with a history of chronic respiratory disease tested positive for avian influenza while hospitalized for gastrointestinal symptoms in September.

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The US Centers for Disease Control and Prevention (CDC) has recorded 52 cases of bird flu in humans since April 2024. But experts believe that this is an approximation. A recent CDC study of 115 dairy workers exposed to infected cows found 7 percent of them. He had antibodies against H5N1 although half of them reported no symptoms.

Although the study was conducted with a relatively small sample of farm workers, “what stands out to us is that we are obviously underestimating the number of human infections,” says Lakdawala. “Many infections that may be asymptomatic or relatively mild do not always elicit a strong antibody response,” which may mean that the study’s antibody test may have missed some cases.

American scientific spoke with flu experts about the latest bird flu cases in humans, preliminary genetic information, and risk of exposure and infection.

Animal droppings

The H5N1 strain currently circulating in North America was mostly in wild migratory birds before it started. release around 2022 in other animal populations such as mink, bears, foxes and marine mammals. Today, the virus in the US largely affects dairy cattle and poultry.

“I think what’s really changed since this particular strain was created is its unique ability to cross over and infect many different mammals,” says Stacey Schultz-Cherry, a St. Jude Children’s Research who studies the ecology of animal and avian influenza. the hospital “There were reports of occasional spills a long time ago, but nothing like what we’re seeing now.”

H5N1 can be highly lethal in poultry, and cattle usually recover from symptoms that include fever, dehydration and abnormal milk production. Lakdawala says the variety of animals affected by H5N1 so far poses a problem in finding sources of human infection.

Source tracking issues

Investigations are underway to identify the sources of infection in the California child and the Canadian teenager. None reported recent exposure to sick wild or farm animals or pets. A Canadian health official he said at the press conference on November 12th as a “very real possibility” investigators will never be able to confirm the source. A sick wild bird may show no symptoms, for example, Schultz-Cherry says.

Genetic sequencing of emerging strains is providing some clues. Test results of the strain that caused the illness in the teenager suggest it is similar to the one present today Circulating birds in Canada. some the scientists marked a specific mutation in a sequence that is important for changing the virus’s receptor preference, perhaps allowing it to bind more easily to human cells. The study observed genetic change associated with viral adaptation to mammals Another recent human case in Texassays Lakdawala. “What this means is that the virus is adapting to humans to get mammalian genetic signatures,” he suggests. “We need to stop the spread of H5N1 in animal species, especially cattle and poultry farms, to reduce possible exposure and spillover to humans. This will prevent the virus from taking so many shots to get the optimal shape of the target mammal.”

Bird flu remains a relatively low risk for most people, but those who work directly with sick dairy cows or poultry are at increased risk. No sustained human-to-human transmission of H5N1 has been observed, but Schultz-Cherry says it’s important to monitor the virus carefully for genetic changes that could allow it to gain this ability or increase the severity of the disease.

Understanding severe infection

In previous appearancesH5N1 has caused severe illness and occasional death in people, Schultz-Cherry says. With the exception of the hospitalized teenager, “we’ve been very lucky that these events have (mostly) been mild, but it’s a little different than what we’ve seen. historicallyand we don’t know why”. Canadian health officials have suggested that the teenager’s critical condition may indicate that the virus may be more severe at a younger age. But the ages of the young people with the latest cases — and most cases of human bird flu this year — have not been made public, further complicating experts’ ability to understand the risk of serious illness.

Lakdawala’s team investigated the role of preexisting immunity—protections developed from past infections, such as seasonal flu—in the progression of H5N1 disease. Findings currently in peer review suggest that the elderly may have cross-reaction of antibodies-The ability of antibodies that originally fight seasonal flu to also respond to H5N1 – compared to younger individuals. This may be because younger children have not encountered this type of flu infection before, Lakdawala explained. “Our immune response will see (a virus) differently based on our previous immunity,” he says, but adds, “I don’t know what this (Canadian) individual’s previous immunity was like.” Schultz-Cherry and Lakdawala say it’s too early to draw conclusions with limited data and information.

There are several tactics to reduce the risk of infection for people at high risk of exposure and farm workers. Washing hands, disinfecting surfaces – including milk and agricultural tools – and using a protective device can help People should generally keep to themselves-and theirs pets—away from and avoid consumption of dead wild birds or animals raw milk and raw cheeses. Getting a seasonal flu shot is especially important this year, Schultz-Cherry says. “We want to do everything possible to avoid giving it (the H5N1 virus). possibility of reorganization” says in a person or animal infected with seasonal influenza. “Can they really share genetic material and have a new virus emerge? I think that’s the biggest concern as we head into the season of human flu.”