Deadly Evolution How Worrisome Is the Possibility of a Bird Flu Pandemic?

To Dr. Robert Hoffman, it matters little that avian flu doesn’t usually attack humans. He doesn’t even consider the question of whether it might someday happen. His question is, when?

“Some people still don’t understand that evolution governs how everything works, from astrophysics to chemistry,” said Hoffman, chief of Infectious Diseases at Mercy Medical Center. “Events seek out these random changes.”

The change he’s speaking of is one that would cause avian flu — which has killed birds, and a few people, around the world — to mutate and gain an ability it does not currently have: transmission from person to person.

“You’d think it’s got to happen at some point. It’s not likely to be a random mutation, though,” Hoffman said, adding that the most likely scenario would involve someone with common influenza being exposed to avian flu, and the two viruses sharing genetic material. A mutation based on those factors is difficult to pull off — but it might, in the end, be inevitable. “Scientists say it is likely to happen at some point.”

The reason that’s a problem is that bird flu typically kills about 60{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} of the humans it infects — virtually all of them people who work with, and even live with, domesticated birds full-time.

For this issue, Hoffman, one of the region’s leading authorities on infectious disease, sat down with The Healthcare News to talk about the danger and perhaps inevitability of bird flu reaching people on a wide scale. But he also spoke of the hope that scientists have of beating a pandemic to the — possibly very deadly — punch.

Straining Possibilities

According to the Centers for Disease Control and Prevention, the avian influenza virus occurs naturally among birds. Wild birds worldwide carry the virus within their intestines, but it usually does not make them sick. However, avian influenza is very contagious among birds and can sicken and kill some domesticated fowl, including chickens, ducks, and turkeys.

Infected birds shed the influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions, or with surfaces that are contaminated.

Avian flu domestic poultry causes two main forms of disease, one a mild form that causes few symptoms and may go undetected. However, the highly pathogenic form spreads more rapidly through flocks of poultry, and has a mortality rate among birds that can reach upwards of 90{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} within 48 hours.

Typically, humans are immune to avian flu, but virtually all known cases in humans have involved people who work and live in close proximity with domestic birds, and have ample opportunity to touch contaminated surfaces and breathe in the dust from the birds’ droppings.

It helps, Hoffman said, to understand what makes avian flu different from the common strains of influenza people deal with every year, usually without lasting harm.

Each year’s chief strain, he explains, usually originates among domestic swine in Asia and passes easily to, and between, humans. But it’s generally preventable with vaccines and treatable with everyday medications.

But while these common strains affect the upper respiratory area, when avian flu infects people, it attacks the lower lung area, which makes it difficult to treat and particularly dangerous, especially if no effective vaccine is available.

“We don’t have much immunity against it, and if it were to attack humans, we don’t have the vaccines to deal with it,” he said. Hoffman suggested that part of the reason avian flu is both less communicable to humans — and less controllable when it does strike — is that people have been living with swine longer than they’ve lived among birds. Whatever the case, a sudden outbreak among humans is a scary thought.

“Mathematically, at some point, that mutation, that series of changes, is going to happen, the virulent strain mixing with the common strain,” he said. “If it gains an ability to attack us and maintains its virulence, that’s the fear.”

In one way, however, the mutation of an influenza virus is just a massive version of the daily, minuscule changes wrought by people taking antibiotics, every time making them less effective in the future.

“Pandemic flu is one minor subset of this process,” Hoffman said. “Every time we write a prescription, we have an effect on evolution. One one level, this is awesome, and on another it’s very satisfying; I really can change this incredibly big process in a small way.

“When I help one patient, it’s the law of unintended consequences,” he continued. “Every time I do that, I set in motion a chain of events that makes it harder to do that the next time.”

That’s why doctors act according to a concept called ‘antibiotic stewardship,’ meaning that they have an obligation to understand this principle when it comes to antibiotics, and to prescribe them cautiously. Unfortunately, the course of sickness and evolution is in other hands as well.

“If a pig farmer in Arkansas decides to give antibiotics to all the pigs on his farm, he starts a process that makes that antibiotic less effective when you want to give it to your child or your grandmother.”

Fear and Hope

Hoffman said an avian flu pandemic would likely behave similarly to the great influenza scourge of 1918, which killed an estimated 50 million people worldwide.

“It attacked people who were young and strong,” Hoffman said. “Usually we worry about the very young and the very old dying, but the 1918 epidemic attacked soldiers, young adults, people in the prime of their lives. They had the highest mortality rates. And in the random cases of bird flu killing people, it was mostly 18- to 40-year-olds.

“The good news,” he continued, “is that we have been working on projects to avert that from happening. The bad news is, some of the answers we thought we had don’t look like they’ll work.”

Tamiflu, for instance, seems to be completely ineffective against the most common strain circulating now, he noted, “so we don’t have any special reason to think it works against avian or pandemic influenza. All those people hoarding Tamiflu to protect themselves wasted a lot of time and probably money. We have no confidence it would work.”

Researchers have experimented with combining Tamiflu and Ramantadine, but cannot tell with any certainty if that cocktail would work, either.

Interestingly, modern vaccines are typically made by growing influenza in chicken eggs — which might be in short supply in case of a worldwide bird flu pandemic. In the meantime, scientists are experimenting with new ways to produce flu vaccines.

However, one development could hold the key to fighting a pandemic: the discovery of a genetic characteristic of influenza that doesn’t appear to change year after year, Hoffman noted.

“That might eventually allow us to create one vaccine you take once, not yearly, for a lifetime of protection against all kinds of flus, and hopefully it will work against bird flu as well as traditional strains.”

Still, Hoffman said, anxiety still exists in research circles over whether the U.S. will continue to fund this work at a sufficient level. “Funding will always be limited, and it’s a moving target. We have to try a lot of different things before we get the right answer — and the right answer today might not be the right answer next year.

“It’s expensive, and there are a lot of needs in this world, and how do you prioritize them?” he continued. “Our attention span is limited, and there are so many crises going on, so will the public support efforts to prevent pandemic flu when, for a lot of them, the question is, how will I pay my mortgage and put food on the table? Those are some urgent, immediate priorities.”

Hoffman paused before offering one perspective.

“I guess the answer,” he said, “is that this is potentially worse than any of the current problems we’re facing.”