Bird flu has reportedly killed a Cambodian girl and sickened others. What you need to know about H5N1

Bird flu has reportedly killed a Cambodian girl and sickened others. What you need to know about H5N1

Updated: 28 days, 10 hours, 10 minutes, 18 seconds ago

An 11-year-old girl has died of bird flu in Cambodia, and multiple others who live in her area sickened, according to media reports, marking the first known H5N1 human infections in the country since 2014—and potentially setting the stage for sustained human-to-human transmission.

The girl, from the southeastern province of Prey Veng, reportedly became ill Feb. 16, suffering from a 102-degree fever, cough, and throat pain. She died shortly after arriving at a hospital in the capital, Phnom Penh, the Associated Press reported, citing the country’s health ministry.

The Khmer Times, a Cambodian news outlet, reported Thursday that 12 additional people from Prey Veng had been infected, citing the health ministry. Four of the 12 have begun to show symptoms, and results of lab testing should be released tomorrow, according to the Times, making it unclear if any have been officially diagnosed so far.

There have been increased reports of H5N1 bird flu spreading among groups of mammals throughout the world in recent days—a situation that must be “monitored closely” due to their physiological similarities with humans, World Health Organization Director General Tedros Adhanom Ghebreyesus said earlier this month.

H5N1 avian flu, rare in humans, is almost always transmitted by direct contact with sick birds. Only rarely have human cases occurred over the quarter century it’s been known to exist, with no sustained transmission reported among humans.

But “we cannot assume that will remain the case,” Ghebreyesus said at a Feb. 8 news conference. If birds have transmitted the virus to small mammals and it’s spreading among them—as seems to be the case, given recent mass mortality events among minks—it could signal that the virus has evolved to more easily spread among humans, experts caution.

While the risk to people remains low, public health officials must prepare “to face outbreaks in humans, and be ready also to control them as soon as possible,” Dr. Sylvie Briand, director of Global Infectious Hazard Preparedness and Emergency Preparedness at the WHO, told Fortune earlier this month.

The report “does raise the concern that we are transitioning from what has been a bird-to-human status quo to more of a human-to-human transmission scenario,” Rajiv Chowdhury, senior epidemiologist and professor of global health at Florida International University, told Fortune.

While 22 chickens and 3 ducks at the now-deceased girl’s home had recently died, and there has been an unusual number of deaths among wild birds in the area as of late, it has not yet been determined how the girl was infected, BNO News reported Wednesday, citing Cambodian government officials. It’s also unclear if the individuals experiencing symptoms who live near the girl had contact with birds.

“I recommend that people do not touch dead or sick birds,” Chowdhury said, adding that children, especially, should be prevented from collecting eggs and/or playing with domestic poultry.

Pathogen surveillance systems must be “strengthened worldwide to prepare and act for any further outbreak,” he added.

A pattern of spill-overs

Even if sustained human-to-human transmission is not taking place in Cambodian, Chowdhury is concerned about a recent pattern of spill-overs from birds to humans “in entirely different parts of the world. A previously healthy Ecuadorian girl was been hospitalized with the virus, and was under sedation and on a ventilator, the WHO reported in January. The girl contracted the virus from poultry her family had recently purchased that died without apparent cause and was recovering, WHO officials told Fortune on Feb. 8, adding that no additional cases were reported in her area.

The likelihood of human-to-human transmission of H5N1 is “very low,” Chowdhury recently told Fortune. But if it were to occur in a sustained manner, it could rock the globe in a way not seen since the 1918 Spanish Flu.

If H5N1 indeed makes a sustained crossover to humans, “the potential impact could be significant,” he said, signifying the start of a “new global influenza pandemic.”

Like the H5N1 flu, the Spanish Flu is thought to have avian origins. And both viruses contain genes that allow them to replicate efficiently in human bronchial cells, according to a 2006 report from the Washington, D.C.-based Population Reference Bureau.

When H5N1 infects humans, the inflammation it causes can lead to lung cells becoming “intensely inflamed”—to an extent not seen in a usual flu. A similar effect was noted in Spanish Flu victims, autopsies of which revealed “lungs choked with debris from the excessive inflammation,” resulting in drowning, the report noted.

While seasonal flu symptoms include fever, cough, sore throat, runny nose, aches, and fatigue, according to the CDC, symptoms of H5N1 in humans are typically much more severe. They include an often high fever, weakness, cough, sore throat, muscle aches, abdominal pain, chest pain, and diarrhea, according to the WHO. These symptoms can quickly give way to difficulty breathing, pneumonia, and/or Acute Respiratory Distress Syndrome, which is often deadly, as well as neurologic effects like seizures.

Because the virus hasn’t crossed over to humans in a sustained manner, it’s uncertain what an easily transmissible human version of H5N1 might look like,  Dr. Jay Varma, chief medical adviser at the New York-based think tank Kroll Institute, recently told Fortune. “But we can guess, based on prior flu epidemics, that it would be very deadly to humans.”

COVID has been “somewhat manageable” because younger individuals are typically less likely to suffer severe disease, he said. The same was not true of the Spanish Flu, which killed more young than old. If human-to-human transmission of H5N1 begins to occur, “we shouldn’t automatically assume that young people or even children will be better protected,” he said. “They may very well be at higher risk.”

This is a developing report and will be updated.