Why COVID-19 Spreads Faster in Some Countries than Others

New study of virus transmission points to the importance of relational mobility.

Posted Nov 20, 2020

Like all viruses, COVID-19 is transmitted via person-to-person contact. Public health records show that the virus has spread much faster in some countries than in others, but the reasons behind the different rates are not fully understood. The proportions of citizens who wear a mask and who maintain social distance are undoubtedly part of the answer, but cultural factors may also play a role. Especially in the first few weeks, before governments introduce lockdown measures.

In a study published last month in the prestigious journal Psychological Science, Cristina Salvador and her colleagues at the University of Michigan examined data from 39 countries to test the relational mobility hypothesis. Simply put, the hypothesis states that viruses spread faster in societies that have high relational mobility (Salvador et al., 2020).

Relational mobility refers to the ease with which people in a society form new relationships and end old ones. It is conceptually related to social openness and individual autonomy. In societies such as Brazil and the United States, which have high relational mobility, people feel free to establish new friendships and dissolve old ones.

In societies such as Japan and Malaysia, which have low relational mobility, people are not as free when it comes to moving between relationships. In these societies, most relationships exist within the context of family, work, and clubs. Many relationships are not chosen; they are given. Relationships in these societies come with significant obligations and responsibilities. Consequently, individuals are hesitant to form new relationships or terminate existing ones.

People who live in societies that are socially open and marked by high relational mobility have more opportunities to interact with strangers and other individuals who are not in a person’s primary social group. As a result, say Salvador and her team, high relational mobility “may put people at particularly high risk for contracting an infectious disease such as COVID-19.”

To test their hypothesis, the researchers analyzed data from 39 countries on six continents. To measure the spread of COVID cases in a country, the researchers used data from Johns Hopkins University to record the daily number of confirmed cases during the first 30 days of the outbreak, with Day 1 being the day when the count of COVID cases first reached 100. The researchers also recorded the daily number of deaths during the first 30 days, with Day 1 being the day when the first COVID death was reported in the country.

To measure relational mobility, the researchers used the results of an earlier study conducted in 2018. Large numbers of adults in every country were recruited via Facebook ads. They completed a 12-item questionnaire that assessed the extent to which they perceive others to be socially open and likely to enter and exit relationships.

To control for confounding variables, the researchers also examined demographic variables that may affect virus transmission rates. For example, COVID-19 may spread faster (and eventually kill more people) in countries that are densely populated, have an older population, and attract large numbers of tourists.

Salvador and her colleagues found strong empirical support for their relational mobility hypothesis. Countries with high relational mobility—the United States, Brazil, and Spain, for example—showed a much faster spread of confirmed cases and more COVID deaths in the first 30 days of the outbreak. Countries with low relational mobility—Japan, Jordan, and Taiwan, for example—showed a slower spread of cases and fewer deaths.

Importantly, the impact of high relational mobility persisted even after Salvador and her team controlled for other variables that could conceivably produce different rates of transmission. The virus spread quickly in countries with large populations and many tourists, for example, but it spread even more quickly when these countries also had high relational mobility.

The impact of relational mobility on COVID death rates was substantial. According to the researchers’ calculations, if the level of relational mobility in the United States was as low as it is in Japan, the number of Americans who died during the first month of the outbreak would not have been 3,417 (the actual number). It would have been 281.

Living in a society that values independence, freedom of movement, and freedom of choice confers many benefits, but it also presents special challenges when the health of its citizens is threatened by a highly infectious disease.


Salvador, C., Berg, M., Yu, Q., San Martin, A., & Kitayama, S. (2020). Relational mobility predicts faster spread of COVID-19: A 39-country study. Psychological Science, 31, 1236-1244.