In the world of human afflictions, the general public often overlooks influenza, considering it an unwanted guest that must be endured during the winter months. But few diseases match the year-in, year-out power of this deadly viral infection. Each year it takes the lives of about 37,000 people in the United States and between 250,000 and 500,000 worldwide. While that toll is significant enough, influenza always has the potential to turn far more lethal, because the viruses can mutate rapidly into new strains. To public health officials, flu tops the list of diseases that could cause a pandemic — a global epidemic.
Influenza got its name in the 1700s from an Italian folk word that attributed colds, cough, and fever to the influence of the stars. Highly contagious, the flu virus passes through the air via water droplets from coughing and sneezing. The organism can survive for hours outside the body. A person infected with flu remains contagious for about a week, beginning one day before symptoms show up.
With its generalized symptoms, the flu mimics the initial stages of many diseases, including the common cold. Flu can be clinically determined by a throat culture and blood test, but by the time results arrive, symptoms may have already run their course. Antiviral drugs can be effective if taken within two days of the start of symptoms.
The flu usually causes fever, body aches, and intestinal problems, as well as upper respiratory tract infections in about 5 percent to 15 percent of the population. Up to 50 million Americans get the flu each year. On average, adults lose three workdays a year as a result. The flu can turn deadly in combination with bacterial pneumonia, an opportunistic infection that attacks flu-weakened lungs. Severe illness affects between three million and five million people each year. The flu is particularly hard on the elderly, who account for 90 percent of the deaths.
Historians believe it was influenza that plagued Greece in 430 B.C.E. during the Peloponnesian War, and that it also ravaged Charlemagne's army in 876 C.E. The first recorded appearance, though, came in New England in 1647, where residents colorfully dubbed the unknown affliction as the "jolly rant," the "new acquaintance," and the "grippe."
New strains of flu arise early each year, and world health officials hurry to identify them in order to develop an effective vaccine. Because the virus mutates so often, immunity doesn't carry over from one year to the next. A flu pandemic sparked by a particularly virulent strain has typically occurred a few times each century, and no one can predict which strain in which year might have global impact. Constant vigilance and early action by global public health authorities is essential because vaccines take six months to produce, test, and distribute — too long to ward off a pandemic once it has taken hold. Another constraint is that at present, vaccines are grown in fertilized eggs, and at any given moment, the number of eggs available in the world is limited. New methods of vaccine production not dependent on eggs are crucial.
Experts agree that another flu epidemic is not only inevitable, but also likely to happen soon. Three times during the 1900s a sub-strain of flu underwent a major genetic change, leading to pandemics: The worse occured in 1918, and there were serious but less dangeours pandemic strains in 1957 (The Asian Flu) and in the 1968 (The Hong Kong Flu). Health officials fear a repeat of the Great Spanish Influenza of 1918, in which an estimated one billion people came down with the disease. Between 21 million and 50 million died — several times the total number of deaths in all of World War I, which ended the year the epidemic began. In the United States alone, 550,000 lost their lives to the disease. Busy gravediggers sang as they worked: "I had a little bird/ Its name was Enza/ I opened the window/ And In-Flu-Enza." As mysteriously as the Spanish flu appeared, it disappeared, leaving health workers to wonder if and when it might return.
A more severe form of human influenza, one that attacks not just the respiratory system but every tissue of the body, can originate in birds, chickens, and pigs. Until 1997, this so-called avian flu hadn't been known to strike humans. But that year in Hong Kong, 18 people came down with severe respiratory disease at the same time a widespread avian flu outbreak hit poultry. Investigations showed that the virus had jumped from birds to humans — the first known instance of that happening.
Within days, Hong Kong authorities destroyed the entire poultry population — about 1.5 million birds — a response that may have averted a pandemic. This avian-to-human transmission of the flu alarmed health officials, and subsequent years have seen minor outbreaks of avian flu in humans elsewhere, including the Netherlands and Vietnam. The real danger is if the avian flu strain evolves from a disease that humans catch from animals to a disease that humans can spread to other humans. The antiviral drug Tamiflu™ may be helpful in fighting symptoms for human victims, and many nations are trying to secure supplies in the event of a large-scale outbreak.
Meanwhile, a new vaccine against the avian flu virus, made by the pharmaceutical company Sanofi Pasteur, has proved effective in 115 volunteer subjects when given in two large doses. While this is hopeful news, critics point out that the large amounts needed mean that the hundreds of millions of doses required to fight a pandemic could never be produced with existing production methods. Vaccines that work at much lower doses are still urgently needed.
Whether the next pandemic originates in humans or birds, its effects will likely be dramatic. An estimated two million to seven million people could die, with tens of millions requiring medical attention. One nightmare scenario: A single person becomes infected with both common and avian flu, allowing the genetic material to mix. The resulting strain would doubtlessly be as lethal as it is contagious.
The key to containing all pandemics is fast action by global health authorities. Western nations stockpile antiviral drugs to protect their own citizens. But rather than combating a virus already spreading globally, health officials suggest rushing drugs and vaccines to the source of the infection and quarantining the area. The goal is to keep the disease from spreading beyond these areas where it breaks out.