Increasing Human H5N1 Cases Stun Experts as Flu Season Approaches

Human cases of H5N1, the avian flu, are on the rise in the U.S., causing concern among health experts as flu season approaches and wild bird migrations are just around the corner.

Recently, Colorado reported an unusual cluster of human H5N1 cases, marking what appears to be the first outbreak in the country. As of Wednesday, there have been nine new cases linked to two poultry farms, along with an earlier case from a dairy farm.

While the number of human infections is much lower compared to the staggering figures of infected birds—more than 100 million since 2022—scientists are worried about the implications of these new cases.

Virologist Angela Rasmussen from the University of Saskatchewan warns that the combination of increasing human infections with the impending flu season could spell trouble. She highlighted the potential for the virus to adapt better to humans, increasing the risks going forward.

The spike in cases was initially reported on July 14, tied to efforts to cull H5N1-infected birds on an egg farm in Colorado. Fortunately, so far, all reported human infections in the U.S. have been mild.

Despite no confirmed human-to-human transmission, researchers noted that the current strain of the virus found in humans is similar to one spreading among dairy cows, raising concerns about potential adaptations that the virus may undergo.

Experts like Matthew Miller, an influenza researcher at McMaster University, caution that we should not be too hasty in assessing the severity of the situation given the small number of infections.

The intertwining of H5N1 infections with seasonal flu could lead to worrying scenarios, according to virologist Tom Peacock. Farm workers getting infected with both strains might create a potent mix, allowing for genetic reassortment that could lead to a new virus better suited to human transmission.

There’s also growing evidence of mammal-to-mammal transmission. A recent study published in Nature revealed genomic sequencing from various infected animals, indicating interspecies transmissions.

With more bird migrations anticipated, the chances for the virus to recombine and evolve could increase dramatically. Experts are particularly worried about the ramifications for U.S. pig farms, which could act as hotbeds for the mixing of influenza strains.

Surveillance efforts in Colorado are ramping up to track human cases of H5N1 more closely, with a new mandatory testing order put into place. However, health officials across the U.S. face challenges due to limited testing and bureaucratic hurdles.

The full extent of H5N1 in humans remains unclear, as highlighted by a recent serology study in Michigan, hinting at possible unnoticed cases. Meanwhile, experts continue to advocate for proactive measures.

As some countries like Finland begin introducing vaccination strategies for at-risk individuals, scientists in the U.S. emphasize that a reconsideration of vaccination for farm workers could be essential, especially given the current situation.