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In 1959, the WHO set out to eradicate smallpox, an ambitious goal that was achieved by 1980. But this goal wouldn't have been possible without coordination on all levels of society. In this episode of Crash Course Outbreak Science, we'll look at cooperation on the individual, community, and national scale and see how by working together we can improve outcomes during an outbreak, prevent future outbreaks, and even eradicate disease.

This episode of Crash Course Outbreak Science was produced by Complexly in partnership with Operation Outbreak and the Sabeti Lab at the Broad Institute of MIT and Harvard—with generous support from the Gordon and Betty Moore Foundation.

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In 1959, the World Health Organization set a goal that seemed impossible: eradicating the infectious disease smallpox. Eradicating smallpox would mean ensuring that not a single person on Earth had the disease, which would stop further outbreaks. That was an ambitious goal. Smallpox killed millions of people every single year, with outbreaks happening all over the world, and even spreading between continents. But, amazingly, by 1980 it had worked! Thanks to effective interventions against individual outbreaks in dozens of countries and mass vaccination campaigns, smallpox was gone. The road to smallpox eradication had plenty of bumps along the way, but the world stayed on track by coordinating at different scales, from international organizations like the WHO to individuals. Today, securing the global health of humanity still requires the same principle. From households and neighborhoods, to governments and nations, it takes participation, communication, and trust between all levels of society to keep ourselves, and one another, safe from outbreaks.

I’m Pardis Sabeti, and this is Crash Course Outbreak Science.

[Theme Music]


While outbreaks often happen at the scale of, say, a neighborhood or city, sometimes we need to look more broadly to find the best prevention strategies and interventions to use. After all, pathogens, the tiny germs responsible for infecting people, can spread between cities, across national borders, and even between different continents, as people travel. If the outbreak spreads to many countries, it could even turn into a full blown pandemic. And there are often similarities between outbreaks in different countries, especially when they’re caused by the same pathogen.

For example, Cryptosporidium outbreaks, caused by a parasite, are often linked to contaminated water supplies regardless of the country they happen in. That’s why the Environmental Protection Agency in the United States considers evidence from outbreaks in European countries to put together national preventative measures like chlorinating water supplies and monitoring them for parasites. So as well as working to keep a local outbreak from going global, we can use strategies that worked in other places to tackle outbreaks in totally different parts of the world. Finding better strategies to prevent and intervene in outbreaks around the world is one reason coordination during an outbreak is so important. We can see how different scales of coordination happen by considering four groups: individuals, communities, countries, and international organizations.

Let’s start off with individuals. Individual people are the ones who could become infected and who might transmit a disease. We also take part in preventative measures, like wearing masks, and can help respond to outbreaks by providing care to others, whether informally or as healthcare workers. Individuals play a key role in disease surveillance, the continuous and systematic process of gathering health data, analyzing and interpreting it. We can volunteer information about ourselves, or the places we’ve been to and whether they’ve implemented safety precautions. That’s vital for planning and implementing interventions at all levels of society, along with getting data to those who need to know. And as we saw for Lyme disease, sometimes a single person can be the one to notice that an outbreak is happening in the first place! Individuals interact with the other groups we mentioned in a few ways. For starters, we’re part of them! Some individuals form members of community health teams, public health agencies or organizations like the WHO who help lead public health responses. Another way to consider individuals is by the communities we’re a part of and interact with. The word “community” often refers to people living in the same area, but it could also mean people who work similar jobs, share a belief system or some other social feature. Communities play a vital role in collectively responding to outbreaks. A neighborhood might organize volunteers to pick up groceries for people who are sick or self-isolating. Communities also take part in disease surveillance. For example, in Kenya, certain towns have led volunteer groups to actively survey households and ask about infections their neighbors experienced. This helps identify people who are susceptible or vulnerable that other parties, like the formal healthcare system, might have missed. When communities share this kind of information with each other, it can keep more people safe. For example, during the cholera outbreak famously investigated by John Snow, many of the people living in the neighborhood near the infected water pump had left before Snow finished his investigation. Even if they didn’t know why the outbreak was happening, they were able to recognize the danger. Of course, this kind of information can also be shared with public health agencies and governments.

In the last episode, we saw that public health agencies are usually funded through national governments. Agencies and governments typically work together to support scientific research and make policy decisions that determine how outbreaks are dealt with across a whole country. As we mentioned for cryptosporidium in the United States, that could mean establishing guidelines for water sanitization and monitoring for pathogens. It could also mean sending officers to specific regions to assist communities responding to smaller outbreaks by setting up clinical testing, running educational campaigns, and other interventions.

But for public health guidelines and interventions to work, public health agencies need to gather evidence on the different communities who could be affected, and actively work with communities to understand their needs. For example, meat from hunted wild animals plays a big role in the livelihoods and food consumption in many West and Central African countries. But the contact between wild animals and hunters poses the risks of an outbreak. Rather than outright banning hunting, national public health agencies can encourage hunters to avoid hunting specific animals, like primates, who pose the biggest risk, while preserving a community’s nutritional needs and way of life. For larger outbreaks, national organizations can coordinate with other countries to manage how they respond. Different countries can connect with each other through public health agencies and research institutions. Other times, the response to an outbreak will be coordinated through a single international body so different countries can come up with an extensive plan of action between them.

We already mentioned one such group: the WHO. Founded in 1948, the WHO is a public health agency that’s part of the United Nations and aims to support health across the globe. Member states, or those countries that agree to be in the UN, contribute resources and expertise to the WHO. Like other public health agencies, the WHO works on many aspects of health, physical and mental, though we’ll focus on its role in infectious disease outbreaks. For starters, during pandemics, the WHO helps gather evidence and coordinate a response between countries. That could involve modeling the pandemic’s future development, working with public health officers and epidemiologists on the ground, or helping research teams in different countries work together to find treatments and cures for the disease. It also sets international standards for how to deal with infectious diseases– basically, it gives advice and assistance to the countries that want it. The WHO represents many countries, but since it’s so large and split across many places, some see it as slow and inefficient. And recently, it’s also been constrained by a lack of money. But it also carries a heavy responsibility, since its actions can affect so many people, and as we’ll see in a moment, has also had many positive impacts on health for the whole world. And like other agencies, they still rely on working with the people who are affected by their interventions for them to be carried out well. So groups of people, big or small, need to be respected and communicated with when undertaking public health activities.

Which is exactly what the WHO aimed to do when it set out to eliminate smallpox in 1959. They made progress with this goal by supporting national vaccination efforts, which in turn cooperated with different communities and the individuals within them. One of the national vaccination efforts the WHO focused on was in Afghanistan. In the early days of smallpox eradication many thought the best approach was to vaccinate as many people as possible. But after seven years, that hadn’t proved very effective in many countries.

One group working to end smallpox in Afghanistan were variolators, people who aimed to deliver smallpox immunity through “variolation.” A precursor to vaccination as we know it today, variolation involves grafting smallpox scabs onto healthy people to give them a milder version of the disease, with the hopes they’d be immune afterwards. Unfortunately, this was much riskier than a modern vaccine, and in some cases caused real outbreaks of smallpox. So, in 1969, the WHO switched tactics, coordinating from the international level, down to individual variolators to help eradicate smallpox in the country.

Let’s go to the Thought Bubble.

 Thought Bubble

First, the WHO worked with the Afghan government to appoint a full time Afghan medical director who would be able to oversee the program for the whole country. They provided the national team with funds, dedicated advisors and staff, vehicles and supplies of vaccines. The national team recognized that different parts of the country needed distinct attention and appointed individual medical officers to different regions. They could appoint their own staff and budget their own resources based on their needs. These regional teams put together vaccination teams to move from village to village. To make sure that the communities in these villages were kept informed, involved and able to give their consent before their visits, the team would send someone ahead of time to speak with village leaders to tell them about the vaccination program and about the hazards of variolation. That way, the villagers understood the program and could provide input, which encouraged and even increased the communities’ participation. For example, there were cultural norms that restricted the kind of touching that was appropriate between men and women, which could have posed an obstacle for vaccinating women in the villages, since most of the vaccinators were men. But by working with the communities, the two groups arrived at a solution appropriate to the cultural context: performing the injections on wrists or forearms, instead of the usual place on the upper arm. Finally, when individual variolators were identified, they weren’t told off or punished, which would have encouraged the practice to continue in secret. Many were recruited to become vaccinators instead, or have their supply of scab material replaced, for free, with vaccines.

Thanks Thought Bubble!


From the international level, right down to individuals, the smallpox eradication program relied on cultural awareness, cooperation, and flexibility to succeed. And thanks to these efforts in different countries, wild smallpox viruses have been wiped off the face of the planet! As we’ve seen, for public health activities to succeed, individuals and communities need to trust the organizations that are working with them. That means that their concerns need to be addressed clearly, compassionately, and comprehensively. One way to do this is by making ways for individuals to make our voices heard, like public health surveys or consultations. Organizations can also be transparent about their decision-making processes, so we understand why we’re being asked to act in certain ways during an outbreak. Without trust and understanding between all levels of society,an outbreak response can be disastrous.

During the AIDS pandemic of the 1980s, public health agencies in many countries either couldn’t, or wouldn’t, properly engage with groups who were susceptible. The CDC infamously called susceptible people the four-H group: homosexuals, heroin users, hemophiliacs, and Haitians, increasing stigma around people within those groups as well as anyone who did have HIV or AIDS. As you can imagine, this destroyed trust between individuals, communities, and the national agencies that should have helped them. As a result, effective interventions often went ignored, so the pandemic spread unchecked for longer than it needed to, leading to unnecessary infections and deaths.

That’s why community engagement, awareness and transparency are so important for responding to outbreaks. When people are uncertain, fearful, or distrustful of organizations that lead public health responses. Or vice versa! They’re less likely to engage with their activities, worsening the effect of outbreaks. Overall, it’s clear that the social environment we inhabit plays a big role in how we’re affected by outbreaks. In our next episode, we’ll be focusing more on the role the physical environment plays in protecting against outbreaks, as well as the risks it can pose to different groups, when we take a look at infrastructure.


We at Crash Course and our partners Operation Outbreak and the Sabeti Lab at the Broad Institute at MIT and Harvard want to acknowledge the Indigenous people native to the land we live and work on, and their traditional and ongoing relationship with this land. We encourage you to learn about the history of the place you call home through resources like and by engaging with your local Indigenous and Aboriginal nations through the websites and resources they provide.

Thanks for watching this episode of Crash Course Outbreak Science, which was produced by Complexly in partnership with Operation Outbreak and the Sabeti Lab at the Broad Institute of MIT and Harvard—with generous support from the Gordon and Betty Moore Foundation. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon.