The infamous Mary Mallon, also known as ‘Typhoid Mary’, provides an early controversial case of asymptomatic infection. Despite infecting over 20 people (of whom 3 died) while working as a cook, she refused to believe that she was asymptomatically infected and contagious, and refused the intervention (gallbladder surgery) that would have cured her infection and prevented further transmission to others, on the basis that she was not ill. As a result of her refusal, she lived in enforced isolation for decades.

The human body harbours at least as many bacterial cells as human cells. Millions of people now, often unknowingly, are asymptomatic carriers of drug resistant bacteria that can be transmitted to others. Around 1.8 billion people carry latent tuberculosis, some of which is multi- or extensively drug resistant. Many sexually transmitted and vector-borne pathogens frequently produce no (initial) symptoms, including HIV, chlamydia, malaria, and Zika, meaning that the true prevalence of these infections is often underestimated. For many pathogens, those with asymptomatic infection outnumber those with overt disease, creating invisible epidemics.

Some asymptomatic carriers may eventually develop symptoms—i.e., disease—from the pathogens they harbour.  Whether they develop disease or not, however, asymptomatic carriers can transmit infection to others—who may develop disease as a result.  For certain pathogens, early detection (e.g., through screening apparently healthy people) combined with intervention (if available) can clear the infection, thus preventing harm to infected individuals and risk to others. Yet, like HIV early in the epidemic, some of the most important asymptomatic infections are difficult or impossible to treat--e.g. drug-resistant bacteria. In cases where no effective treatment exists, some individuals in some contexts are isolated in order to protect others (e.g. carriers of resistant bacteria in hospital).

As detailed in the attached proposal, this workshop will address important and previously unresolved ethical issues raised by asymptomatic infection, including those arising in the cases above.