Polio was almost eradicated. Then came the coronavirus. Then came a threat from President Trump.

For decades, the United States has worked with the World Health Organization and others to quash polio, beating back to near extinction a merciless disease that once paralyzed hundreds of thousands of children each year.

That progress is in danger as the pandemic forces health-care providers to suspend door-to-door vaccination campaigns that have slashed the number of infections.

New cases have emerged in ­Niger and Chad, and fears have mounted about a resurgence in Afghanistan and Pakistan. Although the number of new polio infections has been small — 155 confirmed cases since January — even blips are worrisome, public health experts say, because small increases can trigger explosive outbreaks, especially in poor countries without the resources to combat the virus alone. Continue reading.