Movie Plagues Not Entirely Claptrap

  • by North American Correspondent, MedPage Today

It's a recurring theme -- a plague threatens to kill us all and a few brave souls work tirelessly to prevent doom.

Think "The Andromeda Strain." Think "Contagion" and "Outbreak." On the small screen this year, there's "The Last Ship." And the list could go on.

The consensus among MedPage Today staffers in a morning meeting a few weeks ago was that such fictions are just ... well, fiction. Tinseltown trash. Hollywood hokum.

So we decided to ask the experts and found a consensus among infectious disease specialists that is considerably more nuanced. Such stories are overblown, yes. Sensationalist, of course. But nonsense? Not entirely.

We asked if it is even possible that a sudden pathogenic scourge could threaten to kill us all.

The scientific consensus: Yes, although it's unlikely. But it's likely enough that highly trained specialists spend their working days worrying about it.

Worst Case Scenario (Really)

We also asked: What's the worst that could happen, assuming a novel pathogen, easily transmitted, with no pre-existing immunity anywhere?

The scientific consensus: It could kill a lot of people, but probably not everybody.

"Theoretically, such a pathogen is possible," commented Gail Reid, MD, of Loyola University Health System in Chicago. "It does not need 100% mortality, just close."

"Although in such a case not all humans would die, societal structure would most certainly be negatively affected," Reid told MedPage Today.

And assuming a novel, easily transmitted pathogen, "a large portion of the population of the planet could be affected rather quickly," she said. "Just one plane ride from anywhere in an initially asymptomatic individual has the potential to lead to a pandemic."

"My Infectious Diseases fellows saw the movie "Contagion" several years ago and were very scared. Need I say more?"

Such movies are "fictional, sensationalistic, and raise the specter of extinction events," said Amesh Adalja, MD, of the University of Pittsburgh Medical Center and a specialist in pandemic preparedness.

But "they do reflect the continual threat that humans face from emerging pathogens," Adalja told MedPage Today.

He, like many other experts, cited HIV, SARS, the 1918 pandemic flu, and the recent flu pandemic as examples of novel diseases jumping to humans in recent times. But, as we all know, none has been uniformly fatal.

Lessons From History

"The popular fictional portrayals are not only possible, they have already occurred, "Adalja said, "and preparing, predicting, and attempting to mitigate the effects of this continual onslaught is of paramount importance."

The 1918 flu pandemic "was a vivid example that a novel respiratory virus from another species can effectively mutate to evolve into a competent human pathogen with high potential for person-to-person transmission and virulence resulting in catastrophic illness affecting millions worldwide," said Amar Safdar, MD, of New York University Langone Medical Center in New York City.

That's just the most dramatic example, Safdar told MedPage Today. The "concern for alarm" comes from repeated epidemics and pandemics in the 90 or so years since then.

To fit its movie role, a novel pathogen would need several characteristics -- it would have to be easily transmissible and eventually lethal but with a long incubation period in which the victim was asymptomatic but able to infect many people.

Luckily, we have yet to encounter such a bug.

Robert Holzman, MD, of NYU School of Medicine in New York City, told MedPage Today: "There is no question that infections can have a high death rate and major impact on human and nonhuman populations."

The question, he said, is how likely such an event is.

"Over a lot of years of human existence we have not yet encountered a human pathogen combining the high fatality rate of, say, rabies and the high transmissibility of, say, norovirus or chicken pox or measles," he said.

Possible, Yes. Probable, No

Such a bug is not impossible, he said, but it's "very, very, ..., very unlikely."

"Fortunately," agreed Talia Swartz, MD, PhD, of Icahn School of Medicine at Mount Sinai in New York City, "the notion of a scourge that could instantly wipe out humanity is not a likely event."

Indeed, "it would take an incredibly virulent and contagious pathogen in another species to jump to humans and still be both virulent and contagious," argued Matthew Sims, MD, PhD, of the Beaumont Health System in the Detroit area.

"The big fear is we will hit a perfect storm of disease where all of the worst possibilities come true," Sims said.

"It is very, very uncommon that a disease is so lethal that everyone who catches it dies," commented Jorge Parada, MD, also of Chicago's Loyola University Health System.

Parada, who was a medical source for the 2011 movie "Contagion," added that "even the devastating 1918 flu pandemic that killed an estimated 20 to 40 million people had a mortality rate only as high as around 20%."

Indeed, regardless of the pathogen itself, commented Kevin Morano, PhD, the University of Texas Health Science Center at Houston, some of us would be okay.

"In any population there would almost always be a small percentage of immune individuals, based on chance and genetics," he told MedPage Today. "With a planet of six billion, a 1% survival rate still leaves 60 million."

However, as Loyola's Reid noted, that would still have a devastating effect on human society.

It Really Is a Small World, After All

One thing that worries experts is that we travel a lot more these days. As CDC Director Tom Frieden, MD, is fond of saying, any pathogen is just a plane ride away.

Since the 1918 flu, medical science has gotten better at treating disease, but "the advent of air travel presents a new dilemma, as communicable diseases can now be spread across continents within days," said Glenn Wortmann, MD, of MedStar Washington Hospital Center in Washington, D.C.

SARS in 2002-2003 "highlighted this risk," he said -- an initial outbreak in southern China spread to 37 countries, eventually causing more than 8,000 cases and more than 700 deaths.

SARS was highly virulent, but not completely so, Sims noted: "It stormed through the population but not everyone was affected even among those exposed." But its very virulence meant that the outbreak burned out relatively quickly.

Put another way, some pathogens "kill so fast that the virus becomes self-limiting, unable to spread faster than it kills," Morano said.

For SARS, there is still no established antiviral therapy, commented David Perlin, PhD, of Rutgers New Jersey Medical School in Newark -- the virus was essentially starved of victims by quarantine measures.

(The same is true of the Middle East coronavirus (MERS), incidentally -- there is no specific treatment and control is essentially a matter of good quarantine measures. When they fail, as they did this spring, outbreaks can occur.)

The 2009 pandemic flu, Perlin noted, "was not particularly lethal, but CDC estimated that in approximately one year, there were between 43 (and) 89 million cases."

But a 10% or 20% fatality rate -- like SARS or the 1918 flu -- "would have killed many millions."

Not all diseases burn out, of course. HIV spread for years before it was even recognized and has now killed some 36 million people. Luckily, it's quite hard to catch.

The same is true of the highly pathogenic H5N1 avian flu. It has a case-fatality rate of about 60% -- still not enough to kill us all off -- but only a few hundred cases have been recorded since the bug was first recognized.

"The major worry for scientists," Wortmann said, "is that a deadly virus, such as Ebola, would mutate to become more contagious, and then spread internationally through air travel."

"As there are few effective treatments for viral infections, this would represent a global challenge," he added.

Ebola, now raging in West Africa, is a pathogen with an alarmingly high case-fatality rate but it needs close contact between a victim and another person for infection to take place.

Importantly, it doesn't spread through droplets in the air, as do the flu and common colds. And in places like the U.S. with a highly developed healthcare system, simple barrier precautions and isolation would prevent a widespread outbreak.

Worst case scenarios involve either an antibiotic-resistant bacterium that kills quickly or a virus that kills more slowly or has a latency period where it can be transmitted but is not debilitating, argued UT Health's Morano.

In either case, the rate of infection might be fast enough and the rate of death slow enough that the pathogen could spread by common means of transportation, he said.

It would be even worse if the agent was aerosolized and spread by coughing or sneezing so that many people could be infected by a single patient, Morano added.

The White Knight

But what about the heroes of the tale? What about the brave scientists who track down the pathogen and come up with a cure/vaccine/treatment?

Here the experts are more divided.

Loyola's Reid said: "I think the most fictitious aspect of this is the rapid 'cure' that is developed."

After all, she added, "we still don't have a vaccine for HIV or hepatitis C or Ebola virus, and our vaccine for influenza has to be updated yearly."

On the other hand, Beaumont Health System's Sims said, "technology has come incredibly far in the last decade or so."

It took years for investigators to identify HIV, come up with a test for it, and develop treatments (although no cure or vaccine so far), Sims noted. But it took only a month or so to realize that SARS was a new disease, and a few weeks more to identify the agent that caused it.

Research on possible treatments was underway when the disease had begun to burn itself out.

"Unfortunately, the scenario of an intrepid doc or scientist coming up with a cure or vaccine in the span of a few weeks or months is highly unlikely, especially if the infectious agent is poorly studied," Morano commented.

"These things take a great deal of research, time and money -- exactly what we're doing now in medical centers across the globe."