An amazing event – elimination of influenza in the southern hemisphere during 2020

Amid the tumult of 2020, an amazing benefit of the coronavirus pandemic has been largely missed.

Influenza was stopped in its tracks in the southern hemisphere.

The data based on WHO surveillance reports overlaid with annotation by Marc Bevand (@zorinaq on Twitter) shows the massive gap between expected influenza cases and cases detected by public health surveillance systems during the winter season in the southern hemisphere.

There are several reasons that may explain this.

International travel has been severely curtailed and outbreaks in one country are not spreading widely to other countries. 

Interventions like widespread wearing of facemasks and lockdowns in place, intended to block coronavirus transmission,  are preventing influenza transmission. 

There may also be some interference by active coronavirus infections that is preventing subsequent successful infection by influenza virus, due to the induction by coronavirus of host defence mechanisms like interferon production in the potential host humans for flu transmission. Such interference between viruses was the phenomenon that led to interferon discovery.

These overall findings show that physical and social interventions implemented on a broad scale in the community can bring infectious disease transmission to a halt. In simplified terms, lockdowns work.