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Pandemic Flu

What is Pandemic Flu?

Pandemic flu occurs when a new virus exists to which people have little or no immunity. This new virus will pass easily from person to person. Because the virus is new and people have not had it before, it could cause large numbers of people to become sick or die. A pandemic flu would likely affect businesses, travel and some basic services for a period of time. 

Some Differences Between the Seasonal Flu and Pandemic Flu

Seasonal Flu

  • Caused by influenza viruses that are similar to those already affecting people.
  • Symptoms include fever, cough, runny nose and muscle pain. Deaths can be caused by complications such as pneumonia.
  • Healthy adults usually not at risk for serious complications (the very young, the elderly and those with certain underlying health conditions at increased risk for serious complications).
  • Generally causes modest impact on society (e.g., some school closings, encouragement of people who are sick to stay home).

Pandemic Flu

  • Caused by a new influenza virus that people have not been exposed to before.
  • Likely to be more severe, affect more people, and cause more deaths than seasonal flu because people will not have immunity to the new virus.
  • Symptoms similar to the common flu may be more severe and complications more serious.
  • Healthy adults may be at increased risk for serious complications.
  • A severe pandemic could change the patterns of daily life for some time. People may choose to stay home to keep away from others who are sick. Also, people may need to stay home to care for ill family and loved ones. Travel and public gatherings could be limited. Basic services and access to supplies could be disrupted.

Preparing for Pandemic Influenza: What You Can Do

A pandemic is a global disease outbreak. An influenza pandemic occurs when a new influenza A virus emerges for which there is little or no immunity in the human population, begins to cause serious illness and then spreads easily person-to-person worldwide. The federal government, states, communities and industry are taking steps to prepare for and respond to an influenza pandemic.

A pandemic is likely to be a prolonged and widespread outbreak that could require temporary changes in many areas of society, such as schools, work, transportation and other public services. An informed and prepared public can take appropriate actions to decrease their risk during a pandemic.

Communities, Businesses and Individuals Should:

  • Develop preparedness plans as you would for other public health emergencies.
  • Participate and promote public health efforts in California and your community.
  • Talk with your local public health officials and health care providers; they can supply information about the signs and symptoms of a specific disease outbreak.
  • Implement prevention and control actions recommended by your public health officials and providers.
  • Adopt business/school practices that encourage sick employees/students to stay home.
  • Anticipate how to function with a significant portion of the workforce/school population absent due to illness or caring for ill family members.
  • Practice good health habits, including eating a balanced diet, exercising daily and getting sufficient rest. Take these common-sense steps to stop the spread of germs:
  • Wash hands frequently with soap and water.

  • Cover coughs and sneezes with tissues.

  • Stay away from others as much as possible if you are sick.

  • Stay informed about pandemic influenza and be prepared to respond.

  • Use national and local pandemic hotlines that will be established in the eventuality of a global influenza outbreak.
  • Listen to radio and television and read media stories about pandemic flu.

Pandemic Influenza Questions and Answers

What Is an Influenza Pandemic?

An influenza pandemic is a global outbreak of disease that occurs when a new influenza A virus appears or “emerges” in the human population, causes serious illness in people, and then spreads easily from person to person worldwide. Pandemics are different from seasonal outbreaks or “epidemics” of influenza. Seasonal outbreaks are caused by subtypes of influenza viruses that already circulate among people (for example, influenza A (H3N2) and A (H1N1) viruses have circulated among people since 1977. In contrast, pandemic outbreaks are caused by new subtypes, by subtypes that have never circulated among people, or by subtypes that have not circulated among people for a long time. Past influenza pandemics have led to high levels of illness, death, social disruption and economic loss.

When Did the Last Influenza Pandemic Occur?

The last influenza pandemic occurred in 1968-1969. During the 20th century, the emergence of several new influenza A virus subtypes caused three pandemics, all of which spread around the world within a year of being detected.

The last influenza pandemic in 1968-1969, called the “Hong Kong flu” [A (H3N2)], caused about 34,000 deaths in the United States. This virus was first detected in Hong Kong in early 1968 and spread to the United States later that year. Influenza A (H3N2) viruses still circulate today.

The 1957-1958 “Asian flu” [A (H2N2)] caused about 70,000 deaths in the United States. First identified in China in late February 1957, the Asian flu spread to the United States by June 1957.

The highest number of known influenza deaths from pandemic influenza occurred in 1918-1919 with the “Spanish flu” [A (H1N1)]. More than 500,000 people died in the United States, and as many as 50 million people may have died worldwide. Many people died within the first few days after infection, and others died of secondary complications. Nearly half of those who died were young, healthy adults. Influenza A (H1N1) viruses still circulate today after being introduced again into the human population in 1977.

Both the 1957-1958 and 1968-1969 pandemics were caused by viruses containing a combination of genes from a human influenza virus and a bird influenza virus. The 1918-1919 pandemic virus appears to have a bird origin.

When Will the Next Influenza Pandemic Occur and How Severe Will It Be?

Many scientists believe it is only a matter of time until the next influenza pandemic occurs. The severity of the next pandemic cannot be predicted, but modeling studies suggest that the impact of a pandemic on the United States could be substantial. In the absence of any control measures (vaccination or drugs), it has been estimated that in the United States a “medium-level” pandemic could cause 89,000 to 207,000 deaths, 314,000 to 734,000 hospitalizations, 18 to 42 million outpatient visits and another 20 to 47 million people to be sick. Between 15% and 35% of the U.S. population could be affected by an influenza pandemic, and the economic impact could range between $71.3 and $166.5 billion.

Are There Medicines to Treat or Prevent Pandemic Influenza?

Four different influenza antiviral medicines (amantadine, rimantadine, oseltamivir and zanamivir) are approved by the U.S. Food and Drug Administration for the treatment and/or prevention of influenza. All four usually work against influenza A viruses. However, the drugs may not always work, because influenza virus strains can become resistant to one or more of these medicines. For example, analyses have shown that some of the 2004 H5N1 viruses isolated from poultry and humans in Asia are resistant to two of the medications (amantadine and rimantadine).

More recently, testing of seasonal influenza A (H3N2) isolates from people in the United States during the 2005-2006 influenza season has shown that a high percentage of circulating viruses are resistant to amantadine and rimantadine. As a result, on January 14, 2006, CDC issued a Health Alert Notice (HAN), recommending that neither amantadine nor rimantadine be used for the treatment or prevention of influenza A in the United States for the remainder of the 2005-2006 influenza season. CDC and other public health agencies will continue to monitor both seasonal and bird influenza viruses for resistance to influenza antiviral medications.

Is There a Vaccine to Protect People from Pandemic Influenza?

Currently, there is no vaccine to protect people from pandemic influenza. A vaccine probably would not be available in the early stages of a pandemic. When a new vaccine against an influenza virus is identified, it will take several months before a vaccine will be widely available. If a pandemic occurs, the U.S. government will work with many partner groups to make recommendations guiding the early use of available vaccine.

Useful Information

Download the Home Care for Pandemic Flu

Download the Pandemic Flu Brochure

For more information on what the federal government is doing to prepare for a possible H5N1, visit Pandemic Influenza and the Centers for Disease Control and Prevention.

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