eFlashOnline - Wild polio virus update from WHO as on 26 May 2021 – No new cases are reported during this week. More at http://polioeradication.org/ polio-today/polio-now/this-week/ In 2021 – 2: Afghanistan 1, Pakistan
Polio in Afghanistan: The Current Situation amid COVID-19 in: The American Journal of Tropical Medicine and Hygiene Volume 103 Issue 4 (2020)
Chart: The Long Road to Global Wild Polio Eradication | Statista
Polio was almost eradicated. Then came the coronavirus. Then came a threat from President Trump. - The Washington Post
Global epidemiology of vaccine-derived poliovirus 2016–2021: A descriptive analysis and retrospective case-control study - eClinicalMedicine
What You Need to Know About the Polio Resurgence | ID Care Infectious Disease Doctors
Polio - Our World in Data
Polio Now – GPEI
Which US states have the highest and lowest polio vaccination rates? - ABC News
Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance
Reported cases of paralytic polio, 2021
Africa declared free of wild polio in 'milestone' - BBC News