By Katrine L. Wallace, University of Illinois Chicago

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.

Why are people still getting polio in some countries and in not others? — Mia, age 9, Centennial, Colorado

On a busy street in Karachi, Pakistan, a healthcare worker kneels down so she’s eye to eye with a toddler. She squeezes two drops of liquid onto the child’s tongue. Then she takes out a purple marker and colors the child’s pinkie fingernail so everyone can see that this toddler is now vaccinated against polio.

During big vaccination drives, thousands of health workers like her knock on doors across Pakistan.

Most kids in the United States will never experience anything like this, because they get the polio vaccine as a shot at the doctor’s office instead of drops in a door-to-door campaign.

The two vaccines work a little differently, but both protect kids from the polio virus. The countries that still see polio outbreaks are places where not enough people have gotten the preventive vaccine.

I’m an epidemiologist — a scientist who studies how diseases spread. My work focuses on diseases that vaccines can prevent, and on the false information that keeps some families from getting those vaccines.

A sneaky virus

Polio is caused by a virus that lives in the human gut. It spreads when tiny bits of poop from an infected person get onto hands, food or water, and then into someone else’s mouth. That’s why polio spreads fastest in places without clean water or good sewer systems.

Polio is sneaky. Most people who catch it never feel sick at all, so they can pass it on without knowing.

But in about 1 out of every 200 infections globally, the virus attacks the nerves that control muscles, usually in the legs. This can cause a person to be paralyzed for the rest of their life.

There is no cure for polio. But there is a vaccine, and a few doses can protect you for life.

How vaccines pushed polio back

In 1988, polio paralyzed about 350,000 children in 125 countries. That same year, countries around the world teamed up with one huge goal: Wipe out polio for good.

Though polio has not yet been entirely eliminated, this effort has been a major success. Since then, polio cases have dropped by more than 99% globally.

There used to be three types of wild polio virus. Now, only type 1 is left.

Where wild polio still hides

Wild polio, the original virus, now spreads in just two countries: Afghanistan and Pakistan. In 2025, wild polio paralyzed 52 children there.

Both countries have lived through decades of war. In some areas, it’s too dangerous for vaccinators to travel, and some have even been attacked.

In Afghanistan, vaccinators haven’t gone house to house since late 2024. Families must bring children to central spots, such as mosques, instead. But the kids who can’t get there miss their vaccines.

When too few kids are vaccinated

Some countries have outbreaks of a different kind, called vaccine-derived polio.

The oral polio vaccine, which is no longer used in many countries, including the U.S., contains a weakened polio virus — too weak to make a child sick, but strong enough to teach the body to fight polio.

After a child swallows the drops of vaccine, some of the weakened virus leaves their body in their poop. If nearly every kid around is vaccinated, the virus has nowhere to go and fizzles out.

But in areas where fewer than 80% of kids are vaccinated, it can pass from child to child. Like a message in a game of telephone, the virus changes a little each time it’s passed. Eventually, it can change back into a form that paralyzes children.

That might sound like the vaccine is the problem. But in fact, the problem is that too few kids have received the vaccine.

The children who go unvaccinated are usually the hardest to reach: kids in the poorest families, in faraway villages or in war zones. In one study in Pakistan, offering families other free healthcare along with polio drops cuts the share of never-vaccinated kids nearly in half.

The polio that went nowhere

In October 2025, scientists testing sewage in Hamburg, Germany, found wild polio. Its genes matched a virus found in Afghanistan, more than 3,000 miles (4,800 kilometers) away.

This means that someone carrying the virus, probably without feeling sick, had traveled to Germany. But not a single child there was paralyzed because most German kids are vaccinated against polio.

Other countries in Europe found vaccine-derived polio in their sewage in 2025, with the same happy ending.

Polio can travel anywhere, but it can only hurt kids where they aren’t protected by the vaccine.

When rumors stop vaccines

Polio also gets help spreading from rumors and misinformation. In 2003, false stories that the vaccine was harmful led parts of northern Nigeria to stop vaccinating for almost a year. This led to a small outbreak that spread from that area to other countries.

Research shows that false news online travels “farther, faster, deeper and more broadly than the truth.”

Unfortunately, misinformation could also contribute to a resurgence of polio in places where it has been eliminated — even the U.S. In Colorado, about 1 in 8 kindergartners haven’t had all their polio shots. And in 2022, vaccine-derived polio paralyzed an unvaccinated young man in New York.

Though rumors can travel quickly, trust is built one conversation at a time, by neighbors, religious leaders and doctors who take parents’ questions and concerns seriously.

So close to the finish line

Unfortunately, the budget of the worldwide program to end polio decreased by 30% in 2026, mostly because wealthy countries cut their foreign aid. This cut is largely led by the U.S., which withdrew from the World Health Organization, or WHO, officially in January 2026. Other wealthy donor governments like Germany and the U.K. have also made cuts.

The WHO has warned that these cuts mean that in some places, the fight against polio will not be able to continue.

Only one human disease has ever been wiped off the planet for good: smallpox, in 1980. Polio could be the second. The world has never been this close.

Somewhere today, a healthcare worker is coloring another tiny pinkie purple. Each one breaks a link in the chain that polio needs to survive.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit — adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

This article was provided to Microbial Instincts by The Conversation, an independent nonprofit news organization dedicated to giving you the context to understand what’s going on in the world. Find out more about them or subscribe to their weekly newsletter.

Katrine L. Wallace is an Assistant Professor of Epidemiology and Biostatistics at the University of Illinois Chicago.

She does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Polio Is Almost Gone. Why Is It So Hard to Finish the Job? was originally published in Microbial Instincts on Medium, where people are continuing the conversation by highlighting and responding to this story.

By Rin Reczek, Professor of Sociology at The Ohio State University

Luna, 26, no longer speaks to her father. There was no single betrayal, no dramatic rupture. What ended the relationship was his insistence on obedience and dominance.

“In his head it’s like, ‘I’m the father, you’re the daughters, we do things my way,’” she told me. Luna explained to him that she was “not willing to have a relationship like that,” and her terms for contact were simple: “We could only have a relationship where you understand that I’m a person, and I’m not just gonna do whatever you want me to do whenever you want me to.”

He refused to accept those terms. So after numerous attempts to make it work, she walked away.

Family estrangement has become a fixture of talk shows, advice columns and social media. It’s also the subject of my new book, “Families We Lose.”

Much of the current media coverage on estrangement tends to frame it as an epidemic that is the product of therapy culture.

My research suggests that this framing misses what is actually happening. I conducted 68 in-depth interviews with adults who went no-contact with a parent, sibling, grandparent or other relative. (All participant names, including Luna’s, are pseudonyms used to protect their privacy.)

I found that estrangement is less a story of trauma or selfishness, and more a clash between competing expectations: an insistence on loyalty, duty and forgiveness on one hand, and the longing for respect, emotional safety and personal growth on the other.

Falling birth rates raise the stakes

Estrangement is fairly common.

In a 2022 study, my colleagues and I used national survey data that followed parent-child relationships over several decades. In that period, 26% of adult children in the U.S. experienced a period of estrangement from their fathers, and 6% reported a period of estrangement with their mothers. Our findings were consistent with what sociologist Karl Pillemer found in his 2020 national survey, which showed that 27% of Americans were estranged from a relative, or roughly 67 million people.

Headlines often treat numbers like these as evidence of a sudden crisis. But no study has tracked estrangement rates over time, and nothing in the existing data shows that it is skyrocketing.

Yet estrangement can have different consequences today. People have far fewer children than in most of human history, so the loss of one relationship may carry greater weight. Two generations ago, a parent might have had several other children with whom to maintain close ties; today, many parents have only one or two.

Smartphones, meanwhile, have created expectations of constant contact and connection within families. Even adult children who have quietly distanced themselves by moving away or limiting contact may still find themselves fielding regular requests for connection through texts, phone calls and social media. This can be stressful, emotionally taxing and make it difficult to establish boundaries.

Those I interviewed often had difficult childhoods, and some had experienced abuse. But they rarely pointed to childhood as the proximate cause of the estrangement, instead citing the poor quality of their relationships with parents and other relatives in adulthood.

‘Kinship culture clash’

For them, the path to estrangement was usually gradual, marked by mounting tensions and unresolved conflicts. It emerged out of the recognition that a parent or sibling would not, or could not, treat them the way they desired. For most, this looked like accountability and growth, intentional connection, mutual respect and safety.

Molly, 36, described a lack of accountability as motivation for her estrangement from her mom, Cindy, a decade ago.

Molly told Cindy: “You’ve done all these horrible things. I just need you to acknowledge it. I feel like I’m owed an apology.”

Molly felt that her desire for accountability was a basic need of any relationship, noting, “I didn’t feel like that was asking too much, but apparently it was. I put the ball back in her court, and she’s just sitting on it.”

Most of the people I interviewed recognized that they had different definitions of what family should look like and feel like. In my book, I call this a “kinship culture clash.”

Divorce offers a familiar example of this kind of shift.

For most of American history, marriage was an institution shaped by economics, law, religion and social pressure. You stayed married because that was what one did, and there were few alternatives that didn’t leave one spouse — usually the woman — socially ostracized and financially destitute.

Then, as sociologists Andrew Cherlin, Anthony Giddens and Stephanie Coontz have argued, marriage transformed into a relationship judged by its ability to provide love and support, promote ideals like fairness and lead to personal growth. Once a marriage started being thought of as an arrangement that needed to work for each spouse, divorce became thinkable, then ordinary.

Should family ties always bind?

The family you are born into can carry the same tension.

Ties to parents and siblings are often expected to be permanent and unconditional, reinforced by cultural norms and laws that bind parents and children to one another, even when children become adults. For example, in adulthood, 27 states have filial piety laws that require adult children to bear financial and, in some cases, direct caregiving responsibility for aging parents. This is part of what I term “compulsory kinship.”

Under this framework, you show up at Thanksgiving no matter what was said last year, because your family is your family. You take your dad into your home to care for him when he gets sick, because he’s your father.

This model does help many Americans. It can ensure aging parents have adult children to care for them, while adult children may have a place to call “home,” no questions asked.

In contrast, the estranged people I talked to for my book adhere to what I call “democratized kinship,” and it generally reflects views of contemporary marriage.

Family bonds require mutual respect, reciprocity and support in order to continue. Under this model, genetics take a back seat: Anyone can become family, just like anyone can become a spouse, but no one is automatically family.

Neither family framework is new, and neither belongs to a single generation. Some people have always held family of origin relatives to distinct standards of care. Queer people have been building chosen families for generations.

But what I chart in this book is the conflict between these two ways of thinking.

Estrangement often happens when these two ideas of family collide and cannot be reconciled — when one member insists that biological or origin ties and hierarchies reinforce the family unit, and another insists that behavior does. That is Luna’s story. Her father drew on the logic of age and hierarchy — “Because I’m your father and I said so” — and she demanded to be treated as a person first and a daughter second.

A family that works for you

People who leave their families of origin are not rejecting family altogether.

In a recent study drawing on these same interviews, I show that estrangement operates as a catalyst for what I call “redoing family.”

After cutting off contact with a family member or multiple relatives, people commonly went on to rebuild kinship networks, drawing friends, partners, in-laws and neighbors into roles once reserved for blood relatives, and constructing new family units organized around support and reciprocity.

Luna is not on her own because she no longer talks to her father. Her family today includes her sister, whom she talks to multiple times a day, and a large group of friends.

“I think you can have your chosen family, and whoever in your biological family you connect to,” she told me. “Everybody just gets to choose who they feel they have a real, intimate, deep connection with. And that’s your family.”

She didn’t want less family. She simply wanted a family that works.

This article is from The Conversation, an independent nonprofit news organization dedicated to giving you the context to understand what’s going on in the world. Find out more about us or subscribe to our weekly newsletter.

Rin Reczek is a Professor of Sociology at The Ohio State University. They do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

The real reason many Americans are cutting ties with their parents and siblings was originally published in The Conversation on Medium, where people are continuing the conversation by highlighting and responding to this story.