The premise: On an island off the north coast of Australia, as surfer Charley Williams begins to cough, he is unaware that several dead seagulls and a dead dog lie near him. They are infected with a new form of flu virus, later determined to be an H3N7 mutated variant named "Riptide." Fellow surfer Ames Smith leaves the island and boards a plane to Los Angeles. While on board, he develops a high fever, coughs up blood and dies. The plane and its passengers are quarantined by the Centers for Disease Control and Prevention. A passenger escapes and spreads the virus. Five days later, as several more passengers escape, L.A. has 154 dead and 1,400 sickening. Schools and shops are closed, paper masks are everywhere, mass graves are dug. The city is placed under quarantine. The anti-viral drug "Tana-Flu" is found to be largely ineffective, and a more useful newer drug, "CoToxil," is in short supply. As Riptide spreads, the governor declares martial law and brings in the National Guard. The CDC finally determines that antibodies against tuberculosis bacteria prevent this virus from attaching to the lung, so the blood of TB survivors can be used as a vaccine. The world is saved.
The reality: Though the H5N1 highly pathogenic avian influenza strain has been much publicized and has worried many scientists, it is still primarily a disease in birds, and may not mutate sufficiently to cause the next human pandemic. "If we put all our eggs in this one basket, we can easily miss a mutation in a different virus which becomes the next pandemic strain," says flu researcher Dr. Jeffrey Taubenberger of the National Institutes of Health. The movie sends an important message to the public when it shows a non-H5N1 influenza transforming into the pandemic virus.
The incubation time — or period between exposure and the onset of symptoms — for influenza is two to four days, sometimes longer. The film depicts this waiting period fairly accurately. In real life, scientists are not always sure exactly how influenza is transmitted, and it is unlikely that paper masks would provide much of a barrier to infection. More sophisticated N-95 respirator masks are only occasionally shown in the movie and must be fitted properly to be effective. The movie correctly illustrates the significant downside to quarantining whole regions (as opposed to the more effective strategy of isolating sick patients and their contacts), where people under suspicion become fearful and may take fewer precautions and thereby may spread the virus more widely.
The imagined Riptide virus, like the Spanish flu of 1918, kills a high percentage of older teens and young adults. Some scientists have theorized that this phenomenon is due to a hyperinflammatory response, which causes victims (often young and healthy) to drown in their own respiratory secretions. But Taubenberger believes that the high mortality in young adults in 1918 was likely due to an absence of immunity to the flu strain in those ages as compared to the older population who may have been exposed to a related virus earlier in life.
Coughing up blood is commonly associated with a virus that damages lungs so severely and quickly. But this doesn't happen as commonly as shown in the movie, where practically everyone infected is experiencing hemoptysis.
A virus experiencing a sudden antigenic shift or significant mutation is believed to be the cause of all pandemics. Bringing up this genetic term to explain the suddenly deadly Riptide" virus is a fine bit of scientific detail.
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Less believable is the movie's optimistic portrayal of cooperating government officials, or the science-fiction contention that antibodies against tuberculosis can somehow prevent Riptide from attaching to lungs of potential victims. True, some immunity can be provided by extracting antibodies from the blood of survivors. In Asia, the blood of bird flu survivors has just been shown to protect mice from the disease. But TB is an entirely different disease. You wouldn't expect antibodies of TB sufferers to help fight flu.
Finally, viewers should know that the next flu pandemic may be mild, not massive. Not all pandemics kill many millions like the 1918 Spanish flu.
Dr. Marc Siegel is an internist and an associate professor of medicine at New York University. In the Unreal World, he explains medical facts behind media fiction. He can be reached at email@example.com.