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Coronavirus Is Officially A Pandemic, But What Does That Mean?


World Health Organization (WHO) Director General Tedros Adhanom Ghebreyesus officially declared coronavirus SARS-CoV-2 a pandemic on March 11. The U.S. Centers for Disease Control and Prevention (CDC) updated its Pandemic Preparedness Resources. But after weeks of battling SARS-CoV-2, what does this new categorization actually mean? More importantly, how is it going to change your life?

First, it is vital to understand what a pandemic is. A pandemic is defined as “the worldwide spread of a new disease.” While it can be argued that we knew the spread of coronavirus was global weeks ago, specifics about the geographic spread (not the deadliness) of the virus did not previously qualify it for pandemic status. Experts use the term pandemic when epidemics are advancing in multiple locations on multiple continents at the same time.

What also makes a pandemic classification different from other diseases and illnesses that we see all over the world, such as cancer or dementia, is that it’s infectious. That means it can be spread directly or indirectly from person to person. As of today, the COVID-19 viral disease has been noted in at least 114 countries, infecting more than 120,000 people and killing more than 4,000.

During the WHO’s Feb. 26 mission briefing, the coronavirus had not yet caused a sustained and intensive community transmission. Nor had there been large-scale casualties attributed to the virus above and beyond other viruses.

As Tedros pointed out in that morning’s briefing, the “WHO has already declared a public health emergency of international concern – our highest level of alarm. Using the word pandemic carelessly has no tangible benefit, but it does have significant risk in terms of amplifying unnecessary and unjustified fear and stigma, and paralyzing systems.” He said using the word pandemic at that time two weeks ago “may also signal that we can no longer contain the virus, which is not true. We are in a fight that can be won if we do the right things.”

However, on Wednesday morning Tedros noted that “in the past two weeks, the number of cases of COVID-19 outside China has increased 13-fold, and the number of affected countries has tripled.”

The last time the WHO declared a pandemic was in 2009, when the novel influenza A (H1N1) virus emerged. The virus was first detected in the United States, but quickly spread around the world. Like coronavirus today, when the (H1N1)pdm09 virus began to circulate, few people had any existing immunity.

What makes the H1N1 pandemic different from the coronavirus pandemic in the population response is that many people over the age of 60 were found to have antibodies against the H1N1 virus, but young people were highly susceptible. The opposite has been true with coronavirus SARS-Cov-2, to which older individuals have been the most susceptible.

But the lessons learned from H1N1 should not be forgotten, particularly because it coincided with season flu, and the flu vaccine offered little cross-protection. Further, by the time monovalent (H1N1)pdm09 vaccine was produced, it was not readily available until well after the peak of the outbreak, and a second wave had already taken its place. During that 2009-2010 period, an estimated 60.8 million cases were detected in the United States, resulting in more than 12,000 deaths.

What is the difference between an epidemic and a pandemic? There are many ways to describe the level of disease occurrence, and epidemiological terminology and classifications often get conflated in public dialogue. But there are well defined definitions and classifications for disease measurements.

What makes the classification system hard to understand, and difficult for the WHO and CDC to define, is that diseases change over time. They become more or less widespread, more or less deadly, and thus, the classifications are constantly in flux.

A nice synopsis of the difference on VeryWell Health explains:

  • Epidemic is a term that is often broadly used to describe any problem that has grown out of control. An epidemic is defined as “an outbreak of a disease that occurs over a wide geographic area and affects an exceptionally high proportion of the population.”
  • An epidemic is an event in which a disease is actively spreading. In contrast, the term pandemic relates to geographic spread and is used to describe a disease that affects a whole country or the entire world.

For more information on how the WHO tracks, defines, and determines what becomes a pandemic, the WHO has a public “Stages of A Flu Pandemic” list that can be used as a guide.

  • Phase 1: no viruses circulating among animals have been reported to cause infections in humans.
  • Phase 2: an animal influenza virus circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.
  • Phase 3: an animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level outbreaks. Limited human-to-human transmission may occur under some circumstances, for example, when there is close contact between an infected person and an unprotected caregiver. However, limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to cause a pandemic.
  • Phase 4: is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.
  • Phase 5: is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
  • Phase 6: the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.

To learn more about pandemics, the current state of SARS-Cov-2 and COVIS-19, and track changes in real time, please see the following sites: