We have been inundated with so much information about the 2009 H1N1 that it's hard to keep it all straight. Here's my top ten list of what's most important to know, much of it coming from the website of the Centers for Disease Control and Prevention, which has done a spectacular job of providing timely and useful information:
1) What is the 2009 H1N1 Flu (Swine Flu)?
Different from the typical seasonal influenza virus, this is a new type of flu virus that appeared in Mexico in April, 2009 and soon spread to the United States and around the world. It contains a combination of genetic material found in influenza viruses that infect humans, birds, and pigs. On June 11th the World Health Organization (WHO) declared a phase 6 pandemic -- its highest alert level. On July 16th the WHO called the pandemic the fastest moving pandemic ever.
2) Why are people concerned about the 2009 H1N1 pandemic?
Over the past century, three major pandemics have swept through the world and caused severe illness and death. The most devastating by far was the influenza pandemic of 1918, which killed 40-100 million people worldwide and 500-750,000 Americans at a time when the U.S. population was only about 100 million. The 1957 "Asian flu" caused about 70,000 deaths when the U.S. population was about 170 million. The last pandemic, in 1968, killed about 34,000 out of 200 million Americans.
3) How does the 2009 H1N1 influenza compare to the typical seasonal flu?
Because the 2009 H1N1 virus is new, most people -- especially children and young adults -- have little or no immunity against it. It is spreading more quickly than the usual seasonal flu but seems to be somewhat milder -- though still capable of causing severe illness and death. The typical seasonal flu affects 15-60 million Americans, leading to more than 200,000 hospitalizations. Annual deaths range from 17,000 to 52,000 annually, averaging about 36,000.
The elderly are especially at high risk of seasonal flu, with over 90% of deaths occurring in patients over 65. In contrast, 2009 H1N1 has preferentially affected young adults and children while older patients appear to have some immunity. Only 18% of deaths from H1N1 have been in patients over 65.
It's estimated that between April and June, more than a million Americans became ill from 2009 H1N1; the CDC stopped reporting individual cases on July 24th, 2009. While the vast majority of cases have been relatively mild, as of September 3rd there were 593 deaths and 9,079 hospitalizations in the United States and territories.
For both the regular flu and the 2009 H1N1, certain groups are at increased risk for complications once infected -- children under five, pregnant women, and patients with underlying medical conditions such as suppressed immune systems, asthma, diabetes, neurological disorders, kidney problems, and heart disease as well as adults over age 65.
4) What Can We Expect This Fall?
Flu virus tends to die down over the summer because it survives better when the weather is cold and dry than warm and humid. That's why during our summer the H1N1 virus spreads to the Southern Hemisphere, where it's winter. But the virus never really went away in America and is now surging much earlier than with the regular seasonal flu.
In August, a panel of experts prepared an extensive report for President Obama about the virus. While warning that the exact impact of H1N1 was impossible to predict, the panel outlines a "plausible scenario" that included 60-120 million infected Americans, as many as 1.8 million hospital admissions, and 30-90,000 deaths. Others, including the CDC, have suggested that these estimates are a "worst case scenario."
Unfortunately, the influenza virus is famously unpredictable and the above "plausible scenario" could be way off in either direction. Although the virus is relatively mild now, it can quickly change on its own through mutation and become more deadly. Another way of changing is if two different viruses happen to infect the same cell at the same time. The two different strains could then trade genetic material. Hypothetically, the 2009 H1N1 that is currently sensitive to the antiviral medication Tamiflu could become resistant to Tamiflu if it combines with last year's seasonal flu strain which was 99 percent resistant to the drug. Fortunately, until now the virus has been stable genetically and it remains sensitive to Tamiflu and Relenza.
5) What are the symptoms of the 2009 H1N1?
The symptoms are very similar to those seen with the regular seasonal flu: fever, headache, fatigue, cough, sore throat, runny nose, and aches and pains. In addition, there may be gastrointestinal symptoms such as nausea, vomiting, and diarrhea.
6) How can you catch H1N1?
Just as with the regular seasonal flu, the virus enters your body through your nose, mouth, or eyes. People infected with H1N1 shed virus starting a day before symptoms begin and lasting up to a week or longer in some patients. An uncovered cough or sneeze in a patient with influenza can send infectious virus-filled droplets into the air. If you touch a surface that's infected with flu virus and then touch your mouth, nose, or eyes, the virus can enter your body and cause infection.
7) How do you prevent the seasonal flu and 2009 H1N1?
The most effective way is through vaccination -- assuming you are in a group for which immunization is appropriate. The CDC recommends vaccination with both the regular seasonal flu vaccine, which is already being given, and the 2009 H1N1 vaccine once it becomes available around mid-October. So far, the 2009 H1N1 vaccine has been shown to be safe in adults; the CDC told me this week that studies in children and pregnant women should be done within about 2-3 weeks. Health officials want to vaccinate at least 159 million Americans. Experts predict there will eventually be enough vaccine for all Americans who want it. But only about 45 million doses are expected to be available with the first batch in mid-October.
Those on the priority list to get the 2009 H1N1 vaccine include pregnant women, people in close contact with infants 6 months and younger, health care workers, those ages 6 months to 24 years, and people ages 25 to 64 with serious conditions that put them at high risk for complications from flu.
Experts stress the importance of covering your mouth with a tissue when you cough or sneeze. Wash your hands often with soap and water or an alcohol-based hand cleaner. Remember: you don't get flu from virus that's only on your hands; you get it when you touch your face and give the virus a way to enter your body. Avoid close contact with sick people. And if you are sick with the flu, the current CDC recommendation is to stay home for at least 24 hours after your fever is gone without the use of fever-reducing medication. In some situations, the use of a face mask may be indicated, especially to try to prevent flu in patients at increased risk for complications; click here for the CDC's recommendations.
8) Who should receive treatment with anti-viral medication such as Tamiflu and Relenza?
Last week the CDC said that most people who come down with the 2009 H1N1 flu should just ride it out and not take antiviral medications such as Tamiflu and Relenza. Dr. Anne Schuchat of the CDC said the majority of adolescents, adults and children "can be cared for with mom's chicken soup at home, rest, and lots of fluids." But she stressed the importance of early treatment with antiviral medications -- within 48 hours if possible -- for certain patients at increased risk of complications, especially those hospitalized, under age five, over age 65, or with chronic medical conditions.
A key change in advice from the CDC involves patients at high risk who may have been exposed to the H1N1 virus. Before last week, doctors were advised to give them medication to prevent infection; now doctors are being given the option of "watchful waiting" -- observing the patient closely and only starting antiviral treatment if evidence of flu develops.
9) What warning signs should prompt immediate medical evaluation and treatment?
Click here to watch the interview.