Most of us have experienced influenza at some point in our lives. We're familiar with the fever, the cough, sore throat, runny nose, muscle aches, headaches, and fatigue that are the hallmarks of a bout of seasonal flu. Each year, seasonal influenza infects approximately five million people worldwide and results in between 250,000 and 500,000 deaths, according to the World Health Organization.
But seasonal flu is only half the story. One important characteristic of influenza viruses is that they are constantly changing. The virus accomplishes these changes in two ways; one is called "antigenic drift," which refers to small changes that slowly make the virus unrecognizable to the antibodies that were produced to defend against it. The other form of change is "antigenic shift," which is a sudden and massive shift in the influenza virus' surface proteins, making it radically different from previous strains; therefore most people have no immunity to it 5. These antigenic shifts are the most common cause of flu pandemics.
Pandemic flu is different from the more common seasonal flu because it affects much larger portions of the population due to a lack of immunity. Examples are the swine flu (H1N1) pandemic of 2009 and the far more devastating flu of 1918, also referred to as the Spanish flu, which killed over 25 million people in a single year.
Both seasonal and pandemic influenza raise a host of ethical issues. These resources are intended to assist health care professionals and the general public in thinking through the ethical implications of both types of flu:
Seasonal Flu: Cases and Comments