The Science Behind A Second Wave In A Pandemic

By Ellen Kershner on June 8 2020 in Science

Pandemics can have more than one wave. Photo by Sarah Olive on Unsplash
Pandemics can have more than one wave. Photo by Sarah Olive on Unsplash
  • The 1918 influenza pandemic was the deadliest in history.
  • There have been seven cholera outbreaks, with the first being the 1817 one in India and the most recent was from 2016 to 2020 in Yemen.
  • COVID-19 and influenza are both viruses that cause respiratory disease, but there are significant differences, between them.
  • However, influenzas and COVID are not the same, so theories about second waves are not scientific facts.

As businesses are reopening back up and people are emerging from their homes, many believe that the COVID-19 pandemic’s end is finally beginning. Not all people are ready to come back out and socialize, though. Watching seas of people outside at parks, sunning themselves on beaches, and lining streets in protests are striking fear in many that a second wave of the pandemic is imminent. Everywhere you look, there are people ignoring social distancing rules, not wearing masks, and standing on top of each other, seemingly without much thought to the virus.

Are these fears unfounded, though? The issue is a complicated one. Delving into the science behind a second wave may help clear things up a bit.

Past Pandemics

A second COVID-19 wave is possible. Photo by Victor He on Unsplash

Looking back on history, the 1918 influenza pandemic was the deadliest in history, infecting 500 million people globally and killing approximately 20 million to 50 million. It had three waves, and the second and third ones were more serious, and deadly for people between the ages of 20 and 40.

There have been seven cholera outbreaks, with the first being the 1817 one in India and the most recent was from 2016 to 2020 in Yemen. The 2009 novel influenza virus (H1N1) had two waves, lasting from 2009 to 2010. So, if past history is a predictor, there is a chance that COVID-19 may return.

COVID-19 was first detected in China, and this country was the first to survive its first wave in February 2020 when the number of new cases reportedly dropped to zero in many parts of the country. In mid-May, a new cluster of cases were detected in western Wuhan. This was after 35 days with no new infections. Here is a chart from cebm.net that shows past influenza pandemics and subsequent waves:

Years                    Spread             Season of onset          Notes

1918-20                 Global              USA or China              Two phases, later more severe

1957-58                 Global              China                          Two phases equally severe

2009-10 H1N1       Global              Mexico                        Mild, two phases

COVID-19 and influenza are both viruses that cause respiratory disease, but there are significant differences, between them, including how they spread.  

Second Waves

Pandemics can slow down before reemerging again. Photo by Victor He on Unsplash

Pandemic diseases like these have initial peaks of activity, and then seem to slow down. Past patterns show that they often reemerge in different population segments, and begin to spread again in second waves. This can happen because a disease can affect certain segments of a population first; after these infections decrease, the disease can start to spread in other populations. This is that the 1918-1919 flue appeared to do.

Scientists are working on models of different types of intervention scenarios to analyze the likelihood of a second wave of COVID-19, including the research of aftereffects of limiting interventions that have helped stop the spread of the virus. It has been pointed out that reopening economies prematurely when there are still new cases being reported is likely to cause a second wave.

However, influenzas and COVID are not the same, so theories about second waves are not scientific facts. The scientific community still has a long way to go in understanding this coronavirus, and it is still cloaked in uncertainty. That does not mean that people should throw caution to the wind, though. Preparing for a second wave is essential, as this disease is highly contagious and deadly for older adults and high-risk populations. Even though cases have decreased, living as though the pandemic is done and over with for good is risky, as we may not be out of the woods just yet.

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