The Great Influenza (67 page)

By then the virus had mutated into mild form, or the swine's immune systems had adjusted to it, or both, since the virus alone seemed to cause only mild disease. Shope did demonstrate that with
B. influenzae
as a secondary invader it could still be highly lethal. Later he would show that antibodies from human survivors of the 1918 pandemic protected pigs against this swine influenza.

Shope's work was momentous and provocative. As soon as his articles appeared, a British scientist named C. H. Andrewes contacted him. Andrewes and several colleagues had been expending all their efforts on influenza, and they found Shope's articles compelling. Andrewes and Shope became close friends; Shope even took him hunting and fishing where he had vacationed since he was six years old, at Woman Lake, Minnesota.

In England in 1933, during a minor outbreak of human influenza, Andrewes, Patrick Laidlaw, and Wilson Smith, largely following Shope's methodology, filtered fresh human material and transmitted influenza to ferrets. They found the human pathogen. It was a filter-passing organism, a virus, like Shope's swine influenza.

Had Lewis lived, he would have coauthored the papers with Shope, and even added breadth and experience to them. He would have helped produce another of the seminal papers in virology. His reputation would have been secure. Shope was not perfect. For all his later accomplishments in influenza and in other areas, some of his ideas, including some of those pertaining to influenza, were mistaken. Lewis, if energized and once again painstaking, might have prevented those errors. But no matter.

Shope was soon made a member of Rockefeller Institute. Lewis would likely have also been made a member. He would have been invited into the inner sanctum. He would have had all that he wanted. He would have belonged to the community of those who do science. One could consider Lewis, in a way most personal to him, the last victim of the 1918 pandemic.

AFTERWORD

I
STARTED THIS BOOK
intending to explore not only the 1918 pandemic itself, but also several questions that did not involve influenza per se. One involved how the larger society reacted to an immense challenge. Another confronts anyone making a decision: What process do you follow to collect information that most likely leads to a good one? In short, how do you know when you know?

More narrowly, I also wanted to explore how an investigator should do science, even under the most stressful conditions. William Park, Oswald Avery, and Paul Lewis speak especially to this last point. They were very different people. Each approached science in his own way.

Park saw it as a means to a larger end. To him, a man who almost became a medical missionary, it was a tool to relieve suffering. Disciplined and methodical, he was interested chiefly in immediate results useful for that purpose. His contributions, particularly those made with Anna Williams, were enormous; their improvement of diphtheria antitoxin alone doubtless saved hundreds of thousands of lives over the past century. But his purpose also limited him, and limited the kind of findings he and those under him would make.

Avery was driving and obsessive. Part artist and part hunter, he had vision, patience, and persistence. His artist's eye let him see a landscape from a new perspective and in exquisite detail, the hunter in him told him when something no matter how seemingly trivial was out of place, and he wondered. The wonder moved him to sacrifice all else. He had no choice but to pursue it. Cutting a Gordian knot gave him no satisfaction. He wanted to unfold and understand such things, not destroy them. So he tugged at a thread and kept tugging, untangling it, following where it led, until he had unraveled an entire fabric. Then others wove a new fabric for a different world. T. S. Eliot said any new work of art alters slightly the existing order. Avery accomplished more than that.

Paul Lewis was a romantic, and a lover. He wanted. He wanted more and loved more passionately than Park or Avery. But like many romantics, it was the idea of the thing as much or more than the thing itself that he loved. He loved science, and he loved the laboratory. But it did not yield to him. The deepest secrets of the laboratory showed themselves to Lewis when he was guided by others, when others opened a crack for him, but that crack closed. When he came alone the laboratory presented a stone face, unyielding to his pleadings. He could not find the key, the way to ask the question. Of the three, only he could not penetrate it. And, whether his death was a suicide or a true accident, it killed him.

* 

But one cannot leave this subject without speaking to other questions: the likelihood and potential danger of another influenza pandemic, what we can learn from the one of 1918/1919, and how we can apply those lessons to the emergence of a new pathogen, whether that pathogen is a weapon of terror or a new natural menace - such as Severe Acute Respiratory Syndrome, SARS, the disease which spread from animals to man in the spring of 2003 and threatened to become a major pandemic.

The answer to the first question (the likelihood and potential danger of another influenza pandemic) is not reassuring. Every expert on influenza agrees that the ability of the influenza virus to reassort genes means that another pandemic not only can happen. It almost certainly will happen.

For influenza is not like SARS, which was contained and (as this book goes to press) may have been completely eliminated. SARS, although more lethal even than the 1918 influenza virus, is less dangerous for several reasons.

First, SARS requires fairly close contact to spread, while influenza is among the most contagious of all diseases. Also, in SARS, the virus reaches maximum concentration in the upper respiratory tract, where coughs and sneezes are most likely to spread the virus, a week or longer after symptoms develop. This gives public health officials time to find, identify, and isolate cases. By contrast, the influenza virus can spread from person to person before any symptoms develop, before a victim knows he or she is sick.

If a new influenza virus does emerge, given modern travel patterns it will likely spread even more rapidly than it did in 1918. It will infect at least several hundred million, and probably more than a billion, people. In the United States alone, the Centers for Disease Control estimates that a new pandemic would make between 40 and 100 million people sick. So the prospect is threatening indeed.

If one compares the 1918/1919 pandemic to AIDS, one sees how threatening.

Today the world population exceeds 6 billion. Worldwide, in the twenty-four years since AIDS emerged as a disease, the total death toll is estimated at 24,800,000; at this writing, an estimated 42 million people are currently infected with the HIV virus. In the United States the cumulative death toll from AIDS is 467,910 people.

In 1918 the world's population was 1.8 billion, less than one-third today's. Yet the 1918 influenza virus killed a likely 50 million and possibly as many as 100 million. The AIDS deaths occurred over twenty-four years; most of the influenza deaths occurred in less than twenty-four weeks.

There are now drugs that can contain the HIV virus; the difficulty lies in getting those drugs to the poorest parts of the world as well as in educating people there and in countries, such as China, that continue to minimize the disease. In the United States, those drugs limited AIDS deaths to 8,998 people in the most recent year for which statistics are available.

The U.S. Centers for Disease Control (CDC) estimates that the annual death toll in the United States from influenza now averages 36,000 in a
nonepidemic
year. The 1918 virus killed 675,000 people in the United States, out of a population not much more than one-third the size of today's.

In 1999 the Centers for Disease Control produced a study of what would likely happen if a new pandemic virus struck the United States. It took into account modern medical advances.

Antibiotics would of course significantly cut 1918's mortality rate for secondary bacterial infections following influenza. And several antiviral drugs have demonstrated some effectiveness against influenza. Amantadine and its more recent derivative, rimantadine, block the ability of the virus to build an ion channel between itself and the cell (in effect a tunnel into the cell) it attaches to. When these drugs work, the virus cannot get inside the cell, cannot invade it.

Two other drugs, zanamivir (Relenza), which is inhaled, and oseltamivir (Tamiflu), a pill, take a different approach. Both bind to the viral neuraminidase, so when new viruses try to escape the dead cell they get trapped on the cell surface as if on fly paper. They can't infect other cells. (See the discussion of neuraminidase on page 104.)

All these drugs can reduce the severity and duration of an attack, but only if taken within forty-eight hours after symptoms appear. Taken prophylactically the drugs can also prevent an attack, although the preventative effect does not last long and at this writing the Food and Drug Administration has approved only oseltamivir for this purpose. The virus has also shown some ability to develop resistance to them. So, although antiviral drugs do show progress and promise, they are not an answer.

A vaccine offers far better protection, especially for the elderly. But to make the vaccine, investigators have to aim at a moving target. Every year they try to predict which virus strains will dominate and the direction of antigen drift. Then they design a vaccine for these antigens. When the investigators are right, when they hit their target, the vaccine protects very well for an entire flu season, preventing many attacks and reducing the severity of others. But the vaccine needs to be produced in huge quantities, which takes months, and in that time the virus can mutate in a direction different from the one anticipated. And even if the vaccine includes the right antigens, given the 'mutant swarm' nature of the virus, some viral strains will escape it. Vaccines using killed viruses are injected, but in 2003 a new vaccine (FluMist) was introduced that uses live virus and is inhaled.

The real danger, though, is that it may not be possible to develop and distribute a vaccine in time to protect against a new virus. Influenza viruses for vaccines are grown in chicken eggs. When scientists tried to prepare a vaccine to the H5N1 Hong Kong virus of 1997, the virus initially proved too lethal: the virus killed the eggs in which it was being grown. Ultimately the problem was solved, but developing this vaccine took more than a year. If another lethal virus jumps to humans and it takes that long to develop a vaccine, by then the virus will have done its damage.

So even with all the medical advances since 1918, the CDC estimates that if a new pandemic virus strikes, then the U.S. death toll will most likely fall between 89,000 and 300,000. It also estimates a best case scenario of 75,000 deaths and a worst case scenario in which 422,000 Americans would die.

The CDC based that range, however, on different estimates of the effectiveness and availability of a vaccine and of the age groups most vulnerable to the virus. It did not factor in the most important determinant of deaths: the lethality of the virus itself. The CDC simply figured virulence by computing an average from the last three pandemics, those in 1918, 1957, and 1968. Yet two of those three real pandemics fall outside the range of the statistical model. The 1968 pandemic was less lethal than the best case scenario, and the 1918 pandemic was more lethal than the worst case scenario. After adjusting for population growth, the 1918 virus killed four times as many as the CDC's worst case scenario, and medical advances cannot now significantly mitigate the killing impact of a virus that lethal.

If a new pandemic struck, people suffering from ARDS would quickly overwhelm intensive care units; those with ARDS who did not get true intensive care would have a mortality rate approaching that in 1918. A new virus would also feast on a population that did not exist in 1918 - those with compromised immune systems, including people undergoing radiation or chemotherapy for cancer and transplant recipients, not to mention anyone with HIV.

No one has attempted to estimate the worldwide death toll of another influenza pandemic, but one could easily imagine a lethal virus (even one less virulent than that of 1918) killing tens of millions. No disease, including AIDS, poses the long-term threat of a violent explosion that influenza does.

* 

Investigators and public health officials are not simply sitting back waiting for the next pandemic. In 1948 the World Health Organization established a formal monitoring system for influenza viruses. Currently 110 laboratories in eighty-two countries participate. Four collaborating WHO influenza centers (the CDC in Atlanta and laboratories in London, Tokyo, and Melbourne) provide detailed analysis.

The surveillance has two purposes: first, to track mutations of existing viruses to adjust each year's vaccine, and second, to search for any sign of the emergence of a new strain - a strain that might cause another pandemic. To know where to look matters. Therefore it matters where the 1918 virus crossed into man.

This book hypothesizes that the 1918 virus emerged in rural Kansas. There are, however, other theories. Since influenza is an endemic disease, not simply an epidemic one, and since investigators at that time lacked modern technology's ability to distinguish one influenza virus from another, the only real evidence is epidemiologic. Therefore it is impossible to state with absolute certainty which theory, if any of them, is correct.

Some medical historians and epidemiologists have hypothesized that the 1918 pandemic began in China. Most pandemics whose origin is known did begin in Asia or Russia. There is no scientific reason for this; it is only a question of probabilities. There large numbers of people live in close contact with pigs and birds, so more opportunities exist for a virus to cross over from animals to humans.

British scientist J. S. Oxford believes the 1918 pandemic originated in a British army post in France, where a disease British physicians called 'purulent bronchitis' erupted in 1916. Autopsy reports of soldiers killed by this outbreak (today we would classify the deaths as ARDS) do bear a striking resemblance to those killed by influenza in 1918.