From the article: "Polio was common and has now become rare due to efficient control efforts. This has resulted in a decreased perception of the risks associated with the disease. As the number of cases falls to near zero, the quantity of resources needed to eradicate it may appear disproportionate to the risk. But any breakdown in control efforts will undermine all achievements over the previous decades by leaving open the chance that a small number of cases becomes a large number again. This catastrophic scenario should be avoided. Maintaining polio-free status and going further to eradicate polio still requires considerable efforts from countries and regions. Reducing polio to zero new cases in several regions of the world took decades of a global synchronised effort. A similar global effort resulted in the eradication of smallpox by 1979. Because polio is highly contagious, a single case in one country can undo decades of progress. It can spread across a country as well as across regions where it had previously been eliminated. The most important intervention to stop this from happening is to ensure high vaccination coverage. Countries can be in danger of losing their polio free status if they’re not vigilant. Take the case of South Africa as an example. The country was declared polio-free in 2006 but this was rescinded in 2017 as a result of challenges with several aspects of polio control. There were particular problems with surveillance and vaccination coverage. After these were addressed, South Africa regained its polio-free status in 2019."