TB Contact Tracing Reveals Gender Differences: Public Health Watch

Contact tracing has become a catchphrase as the United States—and the rest of the world—attempts to navigate its way out of the COVID-19 pandemic.

The term is hardly a new one to epidemiologists and public health specialists—and, frankly, politicians and the general public should have been familiar with it as well. If they had been heeding the dire warnings about pandemic infectious diseases, that is.

A new analysis published in the May 2020 issue of Emerging Infectious Diseases (EID) gives us an idea of how contract tracing looks and how its findings can be applied in the management of an infectious diseases—or at least in the setting of tuberculosis (TB). The findings should be particularly informative as various regions across the country begin implementing contract protocols of their own as a way to contain the spread of the new coronavirus, SARS-CoV-2.

First, for the sake of perspective, we should remember that TB is, by far, still the leading cause of infectious disease-related death worldwide. The disease is estimated to cause more than 1.3 million deaths per year globally, with most occurring in the developing world.

Like a certain respiratory virus with which, by now, we are all familiar, M tuberculosis is spread from person to person via airborne transmission. Notably, the disease disproportionately affects men, who account for more than 60% of all confirmed cases.

Again, sound familiar?

It has been theorized that this may be due, at least in part, to gender-based socialization or contact patterns. The thought is that, at least generally, men may have greater contact with other men than with women, at least in many parts of the world.

For their analysis, the authors of the EID paper analyzed 21 social contact surveys from 17 countries to identify patterns relevant to TB transmission. Notably, they found that adults—defined as those 15 years of age or older—surveyed reported more contacts with adults than with children; in all, roughly 90% of all social contacts reported by adults were with other adults.

Men were slightly more likely to have social contacts with other men (44% of all contacts) than women (41% of all contacts). Interestingly, male children indicated a strong preference for “mixing” with adult women (perhaps their primary caregivers), but roughly half of all social contacts among children were with other children.

“Sex differences in social contact patterns are profound, to an extent likely to be amplifying sex disparities in the adult burden of TB in many settings,” the authors wrote. “Differences in sex-specific and age-specific social contact patterns between children and adults suggest a behavioral shift during adolescence, potentially driving the emergence of sex difference in TB epidemiology in adults… Our analysis of social contact patterns across sex and age groups has implications for M. tuberculosis transmission beyond understanding the excess burden of TB in men. Although sex-assortative mixing among adults to some extent protects women from exposure to M. tuberculosis transmission, one third of women’s contacts and one fifth of children’s contacts were with men.”