Influenza pandemics are the stuff of nightmares. My father was able to recall the "Spanish flu" pandemic during the winter of 1918-19, when classes in his Philadelphia grade school were canceled for weeks, shops were closed, and open horse-drawn wagons filled with corpses rumbled through the cobblestoned streets. Fortunately, as an eight-year-old, he could hardly have grasped the big picture—in October 1918, 195,000 Americans died (11,000 in Philadelphia alone). At one point the deaths came so fast that coffins, which were in short supply, were being stolen. Finally, on March 26, 1919, the government announced that the epidemic had killed 583,135 Americans. About half of those struck down were young and healthy.
The extent and impact of the outbreak of swine flu, which appears to have originated in Mexico and is spreading rapidly around the globe, is still unknown, but it has the potential to become an historic pandemic. That possibility appears less likely as the data continue to accumulate. There seems not to be the kind of exponential increase of number of infections that sometimes occurs, for example, with norovirus infections that sweep through cruise ships, dormitories, and other isolated populations. Moreover, the mortality rate -- at least in the United States -- is reassuringly low: the only fatality has been a child transported from Mexico for treatment.
Because of huge discrepancies between presumed cases and confirmed cases, the data from Mexico are virtually impossible to interpret. (They report 27 confirmed cases with seven deaths, while the unconfirmed cases number in the thousands.)
Unfortunately, conditions in many countries are conducive to the emergence of new viruses -- especially flu, which mutates rapidly and inventively. Intensive animal husbandry procedures that place poultry and swine in close proximity to humans, combined with unsanitary conditions, poverty, and grossly inadequate public health infrastructure of all kinds all of which exist in Mexico, as well as much of Asia and Africa make it unlikely that a pandemic can be prevented or contained at the source.
The rapid and constant movement of goods and people around the world makes early containment virtually impossible. We saw this with the SARS (Severe Acute Respiratory Syndrome) epidemic in 2003, when within a matter of weeks, the disease spread rapidly from southern China to infect individuals in some 37 countries around the world, killing about 800; and in the current outbreak, in which New York City high-school students apparently brought the swine flu virus back from Mexico and infected their classmates. In addition, all six cases that have been reported in Canada were connected directly or indirectly with travel to Mexico.
Some background is necessary to understand how such new viruses arise. Flu viruses can be directly transmitted (via droplets from sneezing or coughing) from pigs to people, and vice versa. These cross-species infections occur most commonly when people are in close proximity to large numbers of pigs, such as in barns, livestock exhibits at fairs, and slaughterhouses. And, of course, flu is transmissible from human to human, either directly or via contaminated surfaces.
Pigs are uniquely susceptible to infection with flu viruses of mammalian and avian -- as well as porcine -- origin, which is of concern for a couple of reasons.
First, pigs can serve as intermediaries in the transmission of flu viruses from birds to people. And when avian viruses infect pigs, they adapt and become more efficient at infecting mammals, which makes them more easily transmitted to and more dangerous to humans.
Second, pigs can serve as hosts in which two (or more) influenza viruses infecting an animal simultaneously can undergo "genetic reassortment," a process in which pieces of viral RNA (the virus' genetic material, similar to DNA) are shuffled and exchanged, creating a new organism. The influenza viruses responsible for the worldwide 1957 and 1968 flu pandemics (which killed about 74,000 and 34,000, respectively, in the United States) were such viruses, containing genes from both human and avian viruses.
The production in Mexico of vast numbers of pigs and chickens under relatively primitive conditions and in close proximity to humans (often in small family farms) promotes such "natural experiments" in the production of new viruses.
Experience shows that attempts to stem the spread of an outbreak may actually exacerbate it. In 2006, China's chaotic effort to vaccinate 14 billion chickens to control avian flu was compromised by counterfeit vaccines and the absence of protective gear for vaccination teams, the members of which probably spread disease by carrying infected fecal material on their shoes from one farm to another.
The situation in Mexico resembles the scenario we might expect for an outbreak of a major human-to-human pandemic in its earliest stages: a large number of illnesses among social and family contacts of victims; infection of healthcare workers and patients in hospitals where the victims are treated; and the rapid spread of confirmed cases from an initial region to other countries as people infected by the virus travel while it is incubating, but before they become seriously ill.
No swine flu vaccine is available for humans (and it would certainly take more than a year to design, prepare, test and get approved by the FDA), but because the anti-flu drugs Tamiflu and Relenza have been stockpiled for use in the event of an avian flu pandemic, large amounts of them are available. (Vaccines stimulate the body to mount an immune response to an infectious agent, while drugs act directly on the virus or bacterium to kill it.) However, the drugs must be administered during the first couple of days after symptoms begin in order to be an effective treatment (and are also effective at prevention if administered prior to exposure); and history suggests that when used in poor countries, they often are administered improperly such as in sub-optimal doses in ways that promote viral resistance and actually intensify an outbreak.
While we are waiting to ascertain the breadth and severity of the outbreak, there is much that individuals can do to safeguard themselves and others:
- Avoid unnecessary travel to areas with significant numbers of cases of swine flu.
- Seek medical help (or at least an anti-flu drug, Tamiflu or Relenza, both of which require a physician's prescription) if you think you have actual flu, the symptoms of which include abrupt onset of fever, aching muscles, extreme tiredness, sore throat, and a cough that does not produce sputum. (The flu is not the same as the common cold.)
- If you're given Tamiflu or Relenza, take it exactly when and how prescribed.
- If you get flu, stay home from work or school.
- To avoid becoming exposed or if you have the flu, wear a mask -- an "N-95 respirator," which can be obtained at hardware stores.
- Cover nose and mouth when you cough or sneeze, and discard the tissue after you use it.
- Any surface that others have touched could be contaminated with virus, so wash hands frequently with soap and hot water or with alcohol-based hand cleaners
- Avoid touching eyes, nose, or mouth, which can introduce the flu virus.
- Keep up with the news on the outbreak, and follow instructions from public health officials.
To avoid or mitigate catastrophe, as individuals and collectively we need to be aggressive, smart and resilient. In society, as in evolutionary biology, survival requires nothing less.
Henry I. Miller, a physician and molecular biologist, is a fellow at Stanford University's Hoover Institution. He is a former flu researcher and was an official at the NIH and FDA from 1977 to 1994.