What is Pandemic Influenza?

According to the Centers for Disease Control and Prevention (CDC), 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, and then spreads easily from person to person worldwide.

What is the difference between seasonal flu, pandemic influenza and avian flu?

Avian, pandemic and seasonal influenzas are very different: 

  • Avian influenza is caused by avian influenza viruses, which occur naturally among birds. 
  • Pandemic influenza is flu that causes a global outbreak, or pandemic, of serious illness that spreads easily from person to person. Currently there is no pandemic influenza. 
  • Seasonal flu is a contagious respiratory illness caused by influenza viruses. Click here to access the Hamilton County Health District's seasonal influenza page.


History of pandemic influenza in U.S.

There were three influenza pandemics in the 20th century and experts believe it is only a matter of time before the first pandemic of the 21st century emerges. The worst influenza pandemic, 1918 to 1919, killed about 500,000 people in the United States and up to 50 million worldwide.

While history shows the unpredictable influenza virus is capable of changing and a pandemic will happen at some future date, no one knows where or when that will be.

Avian (bird) influenza

According to the CDC, avian influenza is an infection caused by avian (bird) influenza viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.

Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997. The strain currently circulating in Europe and Asia (H5N1) has made both birds and humans sick.

Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person.

Scientists and public health experts agree that avian influenza (H5N1) circulating in parts of Europe and Asia has the potential to spark a pandemic should the virus mutate and become easily spread among humans. Currently, there is no evidence of avian influenza in the United States.

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Common questions

The possibility of an outbreak of pandemic influenza may be worrisome to many people. Below are some common questions people have about pandemic and avian influenza. Click on each question to read a response from an authoritative agency.

  • Food Safety - Can I get avian influenza from chicken or eggs? 
  • Travel Safety - Is it safe to travel to places where avian influenza has been found? 
  • Vaccine - Will there be a vaccine for avian influenza or other strains of pandemic influenza? 
  • Quarantine - Will I be quarantined if I get avian or another strain of pandemic influenza? 
  • Pet Safety - Are my pets (dogs, cats, birds) safe from avian influenza?

Responding to pandemic influenza nationally and locally


In April 2009, Public health authorities began utilizing years of pandemic flu response plans when H1N1 (Swine) flu emerged. Over 140 vaccination sites - known as Point of Dispensing Sites (PODS) - were established to mass vaccinate groups of the community.  PODS were located in schools and community buildings across the county.  Through the collaborative efforts of schools, fire and police departments, government officials, Tri-state Medical Reserve Corps (TMRC), and nursing agencies, Hamilton County Public Health vaccinated more than 62,000 people within a five month period from October 2009 to February 2010.

Hamilton County Public Health and its partners successfully used the pandemic flu plan during the H1N1 flu response. Many staff, community members, school members and volunteers learned how to effectively and efficiently operate Points of Dispensing Sites, distribute and track inventory supplies, communicate across the county PODS with the HCPH Department of Operations Center (DOC), and provide information regarding the response activities.  Many lessons were learned and improvements were made to the plan in evaluating the response. Click here to read the base plan.  Please note that this continues to be an evolving document and is therefore subject to change without notice.

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