What’s a pandemic? The worldwide epidemic

UPDATE (11-03-2020). After months of deliberation, the World Health Organization has declared COVID-19 a pandemic. As it seemed clear for quite some time, the virus will likely spread to most (if not all) countries on the globe. However, actions can still limit its impact.

COVID-19 has become the most recent pandemic, but it might also be the first pandemic we contain through action.


According to the World Health Organization (WHO), a pandemic is declared when a new disease emerges and spreads around the world, and people have not had time to develop immunity. A disease’s classification as a pandemic is dependent on its geographical spread, but also on its severity.

Pathogen transmission through a population is typically classified in stages of increasing severity.

  • A sporadic infection occurs infrequently and irregularly.
  • An endemic infection describes a disease that normally exists in a certain population, infecting an expected number of hosts in a certain region. Some examples include chickenpox that occurs at a predictable rate among young school children in the United States and malaria in some areas of Africa. refers to the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area
  • An outbreak refers to a sudden spike in the transmission of an infection in a localized region. A prime example is the sudden rise in Ebola infections that occurred in 2019 in the Democratic Republic of Congo. Although 3,296 Ebola cases and 2,196 (67%) deaths have been reported, and the fact that the WHO declared it a public health emergency, the outbreak’s containment meant it doesn’t warrant epidemic status.
  • Epidemics happen when the prevalence of disease becomes significantly higher than the typical expected amount. The term is also used to describe non-infectious diseases such as diabetes and obesity that occur in epidemic proportions.
  • An epidemic generally becomes a pandemic when it spreads all over the world — it is the highest possible level of disease transmission severity.

Is COVID-19 (novel coronavirus) a pandemic?

Images combined from a 3D medical animation, depicting the shape of coronavirus as well as the cross-sectional view. The image shows the major elements including the Spike S protein, HE protein, viral envelope, and helical RNA. Credit: Wikimedia Commons.

The last pandemic was H1N1 influenza (or “swine flu”), which first surfaced in the spring of 2009. It was detected first in the United States from where it spread across the world. From April 12, 2009 to April 10, 2010, the CDC estimated there were 60.8 million cases, 274,304 hospitalizations, and 12,469 deaths. Worldwide, half a million people were killed as a result of the H1N1 pandemic.

Some claimed that the novel coronavirus outbreak that originated in December 2019 in China was on track to become a pandemic. But despite new outbreaks this week in Iran, Italy and South Korea, the WHO was reserved and did not consider COVID-19 a pandemic until March 11.

The number of cases and fatalities seems to be constantly increasing, you can keep track of that here:

The Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the virus belonging to the Coronaviridae family of virusesIts most common symptoms are fever, coughing, shortness of breath and breathing issues. However, many carriers don’t show symptoms, which makes disease transmission particularly difficult to contain. In fact, a new report suggests that most cases in China remain undiscovered because they are very mild.

According to the report, 80% of the cases are mild, 14% are severe, while the remaining 6% become critically ill. In the Chinese province of Hubei, the COVID-19 fatality rate is between 2% and 4%, whereas for the other parts of China, it is around 0.7%.

Although COVID-19 cases have been reported in more than 30 countries, a disease that is present on multiple continents is not necessarily a pandemic. Before declaring a disease as such, the WHO also takes into consideration both how out of control the outbreaks are and the damage they cause.

For example, the 2003 SARS coronavirus outbreak was not declared a pandemic despite affecting 26 countries and killing 774 people.

“Does this virus [that causes COVID-19] have pandemic potential?” Tedros asked rhetorically during the press conference. “Absolutely it has. Are we there yet? From our assessment, not yet.”

In other words, declaring a pandemic does not necessarily involve crossing a threshold of a certain number of deaths or infections, or even a certain number of countries involved. Instead, a disease’s status as a pandemic is reviewed on a case-by-case basis.

“There is an epidemiological definition that includes an infectious disease moving from the original epicentre to at least 2 other continents. The majority of cases outside China have had an index case who has been a traveller from China. The detailed epidemiological data are not available to determine whether every infection had exposure to the index cases or whether there is a second generation of infection; by that, I mean locals who were infected from an imported case have infected their family or other locals. Therefore, without cases in countries outside China representing a second wave (or local epidemic), I understand the reticence of WHO to call it a pandemic,” Marylouise McLaws, a professor at the University of New South Wales’s Health Department, told ZME Science.

To complicate things further, the WHO has stopped using the old system of 6 phases — that ranged from phase 1 (no reports of animal influenza causing human infections) to phase 6 (a pandemic) — to describe infections.

“There is no official category (for a pandemic),” WHO spokesman Tarik Jasarevic said in late February.

Instead, the WHO has declared the COVID-19 infection a public health emergency of international concern, known as a PHEIC, on Jan. 30. This designation, which is still currently in place, aims to help countries with weaker health systems strengthen their defenses, especially in Africa.

At the moment, containment measures in China are going well. However, that can’t be said about developments elsewhere in the world. On February 25, the number of COVID-19 cases outside of China jumped by 26%. By March, several countries have thousands of cases, and the number seems to be growing. Italy has essentially quarantined the entire country, and several countries have banned large public meetings.

Why declare a pandemic?

When a disease is declared a pandemic, governments are more inclined to take more serious containment measures and to fund efforts meant to tackle and control the disease.

For instance, in the event of a pandemic, local authorities generally have procedures in place that they must activate, such as stockpiling antivirals, preparing hospitals for a large influx of patients, and even media awareness campaigns that advise the public to take preemptive measures or stay indoors.

In the United States, once a pandemic is declared, doctors are allowed to use medications outside of the FDA-approved use.

However, declaring a pandemic can also trigger a global-wide panic. As a result, emergency departments at hospitals risk becoming overwhelmed with unnecessary requests. Governments can also overspend on antiviral medications. So, there are good reasons to be reserved about declaring a pandemic, especially if there is evidence that the disease is being contained.

Definitions and terminology aside, the COVID-19 situation remains very serious and health workers all over the world are busy round the clock to contain the infection as long as there’s a window of opportunity.

“Every country has followed China’s led to close borders around centres of their outbreak. This is a difficult decision but the correct one. Environmental cleaning outside where the public is exposed (bus stops, public toilets, etc), home cleaning of surfaces and bathrooms, and isolating the sick are all important infection control measures. One crucial measure is public cooperation; when the authorities request you remain under quarantine, staying at home, hand hygiene, etc. Cooperating with these requests is pivotal to the prevention of the spread,” McLaws wrote in an email.

“Given the ease of spread the control is difficult. If this virus responds to like SARS once the northern hemisphere warms up new cases of COVID-19 will reduce dramatically,” she added.

Pandemics in the future

Some of the worst pandemics in history include the Spanish flu pandemic of 1918, which infected 500 million people worldwide killing 50 million, or the Great Plague of London in 1665, which killed 20% of the city’s population.

The “Asian Flu” pandemic began in East Asia in 1957 after an influenza H2N2 strain spread from Singapore to coastal cities around the world, killing 1.1 million people, including 116,000 in the United States. Another pandemic that originated in Asia was the 1968 Hong Kong Flu, which killed one million people worldwide and about 100,000 in the US alone.

A new pandemic — especially in today’s extremely interconnected world and highly dense cities — is bound to happen. In the past, viruses used to spread with the speed of a steamboat, now they spread at the speed of a jet. Five of the worst pandemics in history, for instance, happened in the previous century. On the flipside, our healthcare system is more advanced than ever and, as our response to the coronavirus has shown, have efficient containment measures to keep outbreaks from getting totally out of control.

If you live close to an area where an outbreak was recently reported, follow these best practices to prevent the coronavirus.

  • Continuously wash your hands;
  • Avoid touching your face with unwashed hands;
  • Avoid crowds;
  • Disinfect your phone once in a while;
  • Stay home if you’re sick. Tell sick colleagues to stay home;
  • Avoid eating raw animal products (especially from infected areas);
  • Avoid travel to countries where infections have been reported.

A COVID-19 vaccine could become practically useful in about 18 months, virologists say.

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