On January 30, 2020, the World Health Organization (WHO) declared the current outbreak of the novel coronavirus “a public health emergency of global concern.” On March 11, WHO characterized COVID-19 as a pandemic. On March 13, the outbreak was declared a (U.S.) national emergency (CDC, March 15, 2020).
A pandemic is a global outbreak of a new influenza A virus (or other virus). Pandemics happen when new (novel) viruses emerge that can infect people easily and spread from person to person in an efficient and sustained way. When a virus is new to humans, very few people have immunity to it, and, as is the case with the COVID-19 pandemic, a vaccine may not be available. The new virus will make a lot of people sick, but just how sick people get will depend on the characteristics of the virus, whether people have any immunity to that virus, and the health and age of the person being infected (CDC, 2016a).
The novel coronavirus is spreading rapidly in China and in other countries as well. But, if the virus is isolated and controlled outside of China, the international cases would simply be called outbreaks. Because there is sustained person-to-person transmission of COVID-19 outside of China, it is now a pandemic.
As of May 21, 2020, the virus has spread throughout the world. Click here for an update on global distribution of the COVID-19.
CDC Pandemic Preparedness
The newly emerged 2019 novel coronavirus is a respiratory virus that seems to be spreading much like the flu. Guidance developed for influenza pandemic preparedness is appropriate now that the current COVID-19 outbreak has triggered a pandemic (CDC, 2020m).
The Pandemic Intervals Framework (PIF) describes the progression of an influenza pandemic using six intervals. This framework is used to guide influenza pandemic planning and provides recommendations for risk assessment, decision-making, and action in the United States. These intervals provide a common method to describe pandemic activity which will inform public health actions. The duration of each pandemic interval will vary depending on the characteristics of the virus and the public health response (CDC, 2016b).
The Six Pandemic Intervals
- Investigation of cases of novel influenza A virus infection in humans.
When novel viruses are identified in people, public health actions focus on targeted monitoring and investigation. This can trigger a risk assessment of that virus to evaluate if it has the potential to cause a pandemic.
- Recognition of increased potential for ongoing transmission of a novel virus.
When increasing numbers of human cases of novel viral illness are identified and the virus has the potential to spread from person-to-person, public health actions focus on control of the outbreak, including treatment of sick persons.
- Initiation of a pandemic wave.
A pandemic occurs when people are easily infected with a novel influenza A virus that has the ability to spread in a sustained manner from person-to-person.
- Acceleration of a pandemic wave.
The acceleration (or “speeding up”) is the upward epidemiological curve as the new virus infects susceptible people. Public health actions at this time may focus on the use of appropriate non-pharmaceutical interventions in the community (e.g. school and child-care facility closures, social distancing), as well the use of medications and vaccines, if available. These actions combined can reduce the spread of the disease and prevent illness or death.
- Deceleration of a pandemic wave.
The deceleration (or “slowing down”) happens when pandemic influenza cases consistently decrease in the United States. Public health actions include continued vaccination, monitoring of pandemic influenza A virus circulation and illness, and reducing the use of non-pharmaceutical interventions in the community (e.g. school closures).
- Preparation for future pandemic waves.
When pandemic influenza has subsided, public health actions include continued monitoring of pandemic virus activity and preparing for potential additional waves of infection. It is possible that a 2nd pandemic wave could have higher severity than the initial wave. An influenza pandemic is declared ended when enough data shows that the influenza virus, worldwide, is similar to a seasonal influenza virus in how it spreads and the severity of the illness it can cause. (CDC, 2016b)