When was the last time you had a cold? Over the past year and a bit, COVID-19 prevention measures have brought a significant recess of once-common infectious lurgies. Unfortunately, it looks like this “ceasefire” has inevitably come to an end. As lockdowns start to ease in some parts of the world, we’re also seeing a resurgence of infectious diseases that were temporarily quelled over the course of 2020. 

Throughout parts of 2020, over half of the world’s population was put under lockdown in an attempt to control the spread of COVID-19. As you’d expect, it wasn’t just this novel virus that found it hard to spread due to the lack of social contact and improved hygiene.

Around late March 2020, when most lockdowns started, the US saw a sharp slump in the number of infections for adenoviruses, bacterial infections, human metapneumovirus, rhinovirus/enterovirus, influenza A, influenza B, parainfluenza, and Respiratory Syncytial Virus (RSV). The 2020–2021 flu season was also exceptionally mild in the Northern hemisphere, seeing a number of cases comparable to those you’d typically see in the summertime. 

Things are starting to look more typical now, however. SyndromicTrends.com, a website displaying trends in the US for various infectious pathogens, shows that levels of human rhinovirus infections (essentially a common cold), as well as parainfluenza, are currently at similar levels seen in June 2019. Meanwhile, norovirus, the much-dreaded virus also called the "winter vomiting bug,” is also making some unpleasant gains. 

Health authorities are starting to take note of these comebacks. On Thursday, June 10, the Centers for Disease Control and Prevention (CDC) warned about a notable increase in rates of interseasonal respiratory syncytial virus (RSV) across parts of the Southern US. A handful of state health authorities have also recently warned of a “significant” increase in norovirus activity in certain areas. 

Back in March 2021, there was a notable outbreak of norovirus in Victoria, Australia, with some 389 outbreaks in childcare facilities and education centers. Victoria’s executive director for communicable disease, Dr Bruce Bolam, told The Guardian that the outbreak could, in part, be blamed on an overreliance on alcohol-based hand sanitizers. While hand sanitizers work well against SARS-CoV-2, the virus that causes COVID-19, they are not very effective against norovirus, which is notoriously hardy and highly contagious. Instead, a thorough hand wash with soap and water is required to effectively reduce the risk of this virus (and most other viruses, including SARS-CoV-2). 

There might be more to come too. While future outbreaks are extremely hard to predict, some scientists are concerned that the world may see a massive bounce-back of many of the infections. A study, published in November 2020 in the Proceedings of the National Academy of Sciences, looked at the impact of the COVID-19 pandemic on future outbreaks of influenza and RSV. They argue that the next few years, especially the winter of 2021–2022, could witness “substantial outbreaks” of RSV infections, as well as influenza.

Gulp.