File image used for illustrative purposes: A member of medical staff holds a swab tested during a drive-thru for the coronavirus disease (COVID-19) testing, at a makeshift centre in Shah Alam, Malaysia April 20, 2020. Image Credit: Reuters

The pandemic that has brought businesses and lives globally to a standstill is believed to have started sometime around mid-November last year. The South China Morning Post traced the first-known instance of the infection to a 55-year-old man, who may have contracted the disease around November 17.

While tracing back the origin and the beginning of the infections could help scientists find a way to combat the COVID-19 disease, a question on the minds of people affected by the pandemic is 'how long will all of this last?'

Past pandemics studied

A new report by the Center for Infectious Disease Research and Policy (CIDRAP), Academic Health Center at the University of Minnesota, focuses on answering this very question. Given how different other coronavirus epidemics such as SARS or MERS are in comparison to the COVID-19 pandemic, the researchers used the influenza pandemics to analyse the possible scenarios that we might see in the future of this pandemic.

Since the early 1700s, at least eight global influenza pandemics have occurred, and four of these occurred since 1900: in 1918-19, 1957, 1968, and 2009-10.


The report said, "Even though coronaviruses are very different from influenza viruses, the COVID-19 pandemic and pandemic influenza share several important similarities." These similarities, according to the study, are as follows:

1.  SARS-CoV-2 and a pandemic influenza virus are novel viral pathogens to which the global population has little to no pre-existing immunity.

2. SARS-CoV-2 and influenza viruses are predominantly spread via the respiratory route by large droplets, but also with a significant component of transmission by smaller aerosols.

3. Asymptomatic transmission occurs with both viruses as well, thereby contributing to the spread of each.

4. Finally, both types of viruses are capable of infecting millions of people and moving rapidly around the globe.

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The report also focuses on a few key differences here;  one is that influenza viruses have a shorter incubation period  (1 to 4 days) vs. COVID-19.

The second one is that, based on reports released so far, 25 per cent of COVID-19 cases are asymptomatic while the asymptomatic ratio for influenza is considerably lower.

Another key finding of difference is that the viral shedding rate for COVID-19 cases, before symptoms show, is higher than the influenza virus, This difference denotes a much higher rate of transmission in the pre-symptomatic phase amid chances of delayed diagnosis.

The number of people who can be infected by one coronavirus case is around 2 to 3 - in some cases as high as tens of people depending on extent of direct contact, asymptomatic stage of carriers etc. This is also significantly higher than any influenza virus pandemic that the world has seen as of now.

What did they find?

The COVID-19 pandemic could last for up to two years.

Based on the behaviour of virus in the influenza pandemics, and correlation with the SARS-CoV-2 virus markers. the experts concluded three possible scenarios. All three scenarios show one thing in common - the pandemic is not going anywhere soon.

The study said, "The length of the COVID-19 pandemic will likely be 18 to 24 months, as herd immunity gradually develops in the human population." The report added that achieving 60 to 70 per cent herd immunity in the population could take time given that the length of such immunity to this virus is not known as of now.

Scenarios - how will it play out

Scenario 1

The first scenario that the experts put forward in what the pandemic will look like sees this wave as the biggest infection wave, which could be followed by smaller waves of infection throughout summer. The first scenario assumes a gradual diminishing of the infections by 2021.

Scenario 2

The second scenario, if it happens, could mean that the worst is yet to come. The experts expect in this scenario that the infection wave will return stronger in fall (autumn) or winter in 2020, followed by one or more smaller waves in 2021. The researchers add: "This pattern is similar to what was seen with the 1918-19 pandemic."

Scenario 3

In this scenario the experts believe it is possible that the first wave of COVID-19 in spring 2020 is followed by a “slow burn” of ongoing transmission and case occurrence, but without a clear wave pattern. This scenario has no precedence in past influenza pandemics, however, could be a possible future for COVID-19 the experts found.

In all three scernarios, the pandemic is expected to last up to two years and well into 2021. The experts concluded, "As the pandemic wanes, it is likely that SARS-CoV-2 will continue to circulate in the human population and will synchronize to a seasonal pattern with diminished severity over time."

Social distancing into 2022

Giving more credence to this outlook, Harvard scientists who modeled the pandemic's trajectory told AFP that a one-time lockdown won't halt the novel coronavirus and repeated periods of social distancing may be required into 2022 to prevent hospitals from being overwhelmed.

The Harvard team's computer simulation, which was published in a paper in the journal Science, assumed that COVID-19 will become seasonal, like closely related coronaviruses that cause the common cold, with higher transmission rates in colder months.

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But much remains unknown, including the level of immunity acquired by previous infection and how long it lasts, the authors said.

However, new facts and data are still being collected about the novel coronavirus - no data sheet about this disease is complete.

"This is an excellent study that uses mathematical models to explore the dynamics of COVID-19 over a period of several years, in contrast to previously published studies that have focused on the coming weeks or months," Mark Woolhouse, an infectious disease epidemiologist at the University of Edinburgh said.

"It is important to recognize that it is a model; it is consistent with current data but is nonetheless based on a series of assumptions - for example about acquired immunity - that are yet to be confirmed."