The Viral Storm (12 page)

THE FIRST PANDEMIC

In early July 2002 in Franklin County, Tennessee, a thirteen-year-old boy named Jeremy Watkins picked up a sickly bat on his way home from a day of fishing. None of the other family members handled it, and his stepfather wisely made him release the animal soon after Jeremy revealed his find.

Events like this happen all over the world with thousands of wild animals every day, largely without ill consequences. But Jeremy’s encounter with this particular bat would be quite different.

In the CDC report that would document Jeremy’s case, the next events were described with clinical efficiency. On August 21 Jeremy complained of headache and neck pain. Then a day or so later his right arm became numb and he developed a slight fever. Perhaps of greater concern, he also developed diplopia, or double vision, and a constant, queasy confusion. Three days later he was taken to the local hospital’s emergency room but was discharged with the incorrect diagnosis of “muscle strain.” The next day he was back in the emergency room, this time with a fever of 102°F. He had the same symptoms, but now his speech was slurred, he had a stiff neck, and difficulty swallowing.

At this point, Jeremy was transferred to a local children’s hospital. By August 26 he could no longer breathe or think normally. He was also producing copious amounts of saliva. Highly agitated to the point of being combative, Jeremy was sedated and put on life support. His mental status deteriorated rapidly and by the next morning he was completely unresponsive. On August 31 Jeremy was pronounced brain-dead and, following the withdrawal of life support, he died of bat-borne rabies.

Jeremy’s family did not know that bats could carry rabies, much less transmit it to humans. They did not remember him complaining of a bite, although that’s exactly what must have happened while he carried the bat home from his fishing excursion. They probably did not know that the incubation period for rabies is generally three to seven weeks, well within the range of the time between his exposure to the bat and the first symptoms he experienced. Detailed studies of the virus that killed Jeremy revealed evidence of a variety of rabies found in silver-haired and eastern pipistrelle bats common in Tennessee.

Rabies is a terrible way to die. It’s a disease that devastates the families of its victims, with patients becoming virtual zombies in the days before death. It is among the small number of viruses that kill virtually all of the individuals they infect. But as tragic as it is that the doctors at the local Franklin County emergency room sent Jeremy home with a diagnosis of muscle strain, the reality is that it was already too late to help the boy at that point. Without rapid postexposure prophylaxis after infection, the boy was destined to die.

*   *   *

If we take a different view, the virus that causes rabies is not only a deadly menace but also a truly amazing feat of nature. This virus, shaped like a bullet, is a meager 180 nanometers long and 75 nanometers across. If you stacked rabies viruses one on top of the next, you would need more than a thousand of them to reach the thickness of a single human hair. Rabies has an almost trivial genome, with only twelve thousand bits of genetic information for a meager five proteins. It’s simple, tiny, and incredibly powerful.

While diminutive, the virus accomplishes remarkably sophisticated tasks. In addition to the standard viral work of invading cells, releasing genes, making new viruses, and spreading, it has some unique tricks. From the point of entry, the virus travels preferentially along neural pathways, making its way into the central nervous system. It accumulates selectively in the saliva. The virus particles that infect the central nervous system modify the host’s behavior, increasing aggression, interfering with swallowing, and creating a profound fear of water. When put together, a rabies infection leads to an aggressive host literally foaming at the mouth with virus. A host that lacks the capacity to drink or swallow further increases the probability of delivering a successful bite—a bite that gives this particular virus the ability to advance from one individual to the next.

Hospitalized human rabies victim in restraints.
(
Courtesy of the Centers for Disease Control
)

As frightening and deadly as rabies is, as a global community we need not fear it. That a virus is exceedingly and dramatically deadly does not mean it will become a pandemic. Rabies kills more than fifty-five thousand people a year worldwide. It is a cause for serious public health measures, but it does not present a global pandemic threat. In all of the years that the CDC and other public health organizations have followed rabies, it has never once gone from person to person. Every one of those deaths, like the death of Jeremy Watkins, resulted from an independent animal infection. From a pandemic perspective, it doesn’t have the right stuff.

*   *   *

So, what
is
a pandemic? Defining them creates some trouble. The word itself comes from the Greek
pan
, meaning “all,” and
demos
, meaning “people.” Yet, in reality, it is almost impossible to imagine an infectious agent that infects the entire human population, a high bar to set for a virus. In humans or any hosts, different individuals will have different genetic susceptibility, so at least a few individuals will likely be incapable of sustaining an infection because of some kind of genetic immunity. Also, the simple logistics of spreading to every single individual in any population makes such a feat nearly impossible.

Among the most common viruses infecting humans that we are aware of is the human papilloma virus,
1
and it doesn’t afflict 100 percent of people. HPV currently infects 30 percent of women between the ages of fourteen and sixty in the United States, a whopping high rate for a virus. Rates are likely even higher in some parts of the world. Amazingly, the majority of sexually active humans on our planet, whether male or female, will get HPV at some point in their lives. The virus is made up of over two hundred different strains, all of which infect either skin or genital mucosa. Once the virus enters an individual, it generally stays active for years or even decades. Fortunately, the vast majority of HPV strains cause no problems for us. The few strains that do cause disease generally do so by causing cancer, the most important example being cervical cancer.
2
Luckily, most HPV simply spreads from individual to individual with little harm.

We’re still aware of only a small percentage of all viruses that call humans their home. There may be viruses out there that infect even more people than HPV does; the work to identify all of the viruses that infect us has only just begun. Research over the last ten years has identified multiple previously unknown viruses circulating in humans that infect many individuals yet do not appear to cause any illness. The TT virus was named after the first individual to be infected, a Japanese man with the initials T.T. Very little research has been done yet on TTV, but it may be quite common in some locations. A report by one of my collaborators, Peter Simmonds, an excellent Scottish virologist, found prevalence rates ranging from 1.9 percent among Scottish blood donors to 83 percent among residents of The Gambia in Africa, a startlingly high range. Fortunately, TTV does not appear to be harmful.

GB virus is another recently identified and still largely unstudied virus present in many people. The virus got its name from a surgeon, G. Barker; at the time, his hepatitis was mistakenly attributed to the virus.
3
I know from my own work how common both TTV and GBV are. Using very sensitive approaches to viral discovery, we frequently see these two—largely to our dismay, since they interfere with our ability to catch the dangerous culprits we’re really looking for.

However common TTV and GBV are, they do not infect 100 percent of humans. So the literal Greek-derived definition of
pandemic
is probably an impossibility. The World Health Organization (WHO) has devised a six-stage classification of pandemics beginning with a class-one virus that infects just a few people and going on to a class-six pandemic, which occurs when infections have spread worldwide.

The WHO faced widespread criticism for labeling H1N1 a pandemic in 2009, but that’s exactly what it was. H1N1 went from infecting only a few individuals in early 2009 to infecting people in every region of the world by the end of the same year. If that’s not a pandemic, then I don’t know what is. Whether or not we label a microbe that’s spreading as a
pandemic
is unrelated to its deadliness. It’s just a marker of its ability to spread. And as we discussed in chapter 1, the fact that H1N1 doesn’t kill 50 percent of the people it infects (or even 1 percent for that matter) doesn’t mean it won’t kill millions of people or represent a massive threat.

In fact, from my perspective, it’s possible that we could have a pandemic and not even notice it. If, for example, a symptomless virus like TTV or GBV were to enter into humans today and spread around the world, we probably wouldn’t be able to tell. Most conventional systems to detect diseases only catch things that cause clear symptoms. A virus that didn’t cause any immediate harm would likely be missed.

Of course, “immediate” isn’t the same thing as “never.” If a virus like HIV were to enter into humans today and spread globally, it wouldn’t be detected for years, since major disease would occur sometime after initial infection. HIV causes only a relatively minor set of syndromes immediately, even though it starts to spread right away. AIDS, the major disease of HIV, doesn’t emerge until years later. Since conventional methods for detecting new pandemics rely primarily on seeing symptoms, a virus that spreads silently would likely miss our radar, spreading to devastating levels before an alarm could be triggered.

Missing the next HIV would obviously be a catastrophic public health failure. Yet new viruses, even if likely to be completely harmless, like TTV and GBV, need to be monitored if they are moving quickly through the human population. As we saw in chapter 1, viruses can change. They can mutate. They can recombine with other viruses, mixing genetic material to create something new and deadly. If there’s a new virus in humans and it’s spreading globally, we need to know about it. The dividing line from spreading and benign to spreading and deadly is a potentially narrow one.

*   *   *

For our purposes, we’ll define a pandemic as a new infectious agent that has spread to individuals on all continents (with the exception, of course, of Antarctica). One may counter that it would theoretically take only a dozen or so infected people to accomplish this—a few infected people per continent. That may be true, but it would be exceptionally rare for a microbe to spread so widely and infect so few individuals. And if it did manage to occur, even with twelve people, it would still represent a potent risk to all of us.

Defining precisely when a new spreading agent actually becomes a pandemic is less important for our objective here than understanding how pandemics are born. What I wanted to know when I began my research on pandemics was how something goes from being a strictly nonhuman infection to one spreading to humans on every continent.

In 2007 I worked with the aforementioned polymath biologist and geographer Jared Diamond and the tropical medicine expert Claire Panosian to develop a five-step classification system for understanding how an infectious agent living exclusively in animals can become an agent that spreads globally in humans. The system moves stepwise from agents that infect only animals (Category One) to agents that exclusively infect humans (Category Five).

Jared and I spent many afternoons pondering this process over extended writing sessions at his home in Los Angeles. During our lunch breaks, we’d stop writing to brainstorm, using thought experiments, how a virus might make this jump. We came up with one fairly elaborate idea centered around the Diamonds’ geriatric but much beloved pet rabbit, Baxter, and his invented disease—the dreaded Baxterpox. Even in our imaginary world, most human diseases have their start in animals.