How to think about bird flu severity and evolution.

Welcome to Not a Doctor. I’m Melody Schreiber, a journalist and the editor of What We Didn’t Expect: Personal Stories About Premature Birth.

Earlier this month, a teenager in British Columbia developed flu symptoms and, a few days later, had to be hospitalized. At the hospital, they discovered the teen had H5N1, the highly pathogenic bird flu.

The teen is in critical condition with acute respiratory distress, a really scary condition. There’s been “no change in condition of the young person,” Bonnie Henry, the provincial health officer at the British Columbia Ministry of Health, told me.

In the meantime, scientists studying the genomic sequence of the virus discovered something else that is potentially worrying: It seems like there is a mutation in the same spot that has been linked to higher transmissibility among people.

I wrote about it for The Guardian today:

That could indicate that H5N1 has the capability to become more like a human virus, rather than an avian virus, but it is also not clear yet whether this change is meaningful and more dangerous to people, experts said.

“It’s not quite clear what the real-world implications are going to be, but certainly all of these things are a warning sign,” said Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan.. “We really do need to pay attention to this, and we really do need to try to reduce more human infections as much as we possibly can.”

“We need to be following this as closely as we can. Any advanced warning we can get that there’s more viruses making these types of changes, that’s going to give us the heads-up,” said Richard Webby, a virologist at St. Jude Children’s Research Hospital’s department of infectious diseases.

How the teen even got sick is another major question. I go into more detail about all of this, so I hope you’ll read the piece.

Today I also wanted to talk about what this means for human-to-human transmission and virulence (how sick a virus makes us).

Looking for potential mutations is “a great system for getting an early warning, but it’s also not proof that something’s going to work that way,” Angela Rasmussen told me. “It gives us an indication of what could happen, but it doesn’t tell us what’s going to happen with this.”

Adaptations for humans are worrying because they can signal the next step toward human-to-human transmission and that an outbreak is gaining ground among people.

But at this point, there doesn’t seem to be “any indication at all that there’s human-to-human transmission,” Rasmussen said.

That’s reassuring! The leading theory seems to be that the teenager may have gotten sick from a pet that encountered wildlife.

But why did the teen get so sick? Could the mutation have caused more severity?

Here’s how Richard Webby thinks this mutation happened:

“This individual probably got infected with a normal avian virus that looked like every other avian virus. But then, for whatever reason, there was severe illness in this individual, the virus grew for a little bit longer, maybe in different parts of the body, and then it started to develop these adaptive mutations later on.”

That means the teen may have gotten very sick before the virus mutated, he said. “In that case, the link between these mutations and any sort of severe disease, I think, is wrong.”

Added to that: The science behind looking for possible mutations only checks for increased transmissibility, not virulence, Rasmussen said.

And severity has a lot of factors that have nothing to do with the virus itself.

“In my view, one of the most important things that people need to consider is the route of transmission,” Rasmussen said.

Touching infected animals or infected milk is “very different from inhaling a dose of the virus. If the virus isn’t getting to the tissue where it’s going to cause severe disease, then the disease severity is going to be less,” she said.

How severe illness is also depends on the person who gets sick.

So far, farm workers haven’t reported any severe illness from H5N1, but it’s important to keep in mind that farm workers tend to be extremely strong and healthy — and they also have pretty good reasons not to report illness, because they might lose their job or even their status in this country.

And the only person in the U.S. who tested positive and wasn’t a farm worker was hospitalized — though, thankfully, not in the ICU, and they recovered.

So we can’t really look at these cases to understand if a strain of H5N1 is milder or more severe, because the known cases so far have been pretty limited demographically.

I’m still very worried about what this virus could do among the general population, as well as among farm workers who still aren’t getting the protections they need.

It’s reassuring that the virus does not seem to spreading from person to person. If you work with poultry or dairy cows, you should take as many precautions as possible. Same with anyone hunting wild birds, or with wildlife veterinarians.

For the rest of us, we should try to limit our pets’ contact with wild animals, especially birds. Don’t let your dog or cat go sniffing around any dead birds. Don’t drink raw milk.

Even as I remind you (and myself) that the risk to most people is low, as I try again to think of practical ways to protect ourselves, my mind invariably returns to the hospitalized child in British Columbia.

I hope they pull through. It doesn’t seem like enough to say that; it feels terrifyingly passive, the invocation of thoughts and prayers. I think about the steady whoosh of ventilators, the beeping machines monitoring each breath and beat of the heart.

Hope doesn’t seem like enough. But hope is what we have right now.

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