Zoonoses and wet markets: beyond technical interventions

Following initial suspicions that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might have emerged in a wet market in Wuhan, China, calls have been made to ban wet markets¹ or implement technical interventions mitigating disease risk while minimising business disruptions.² Regardless of the role of wet markets in the emergence of SARS-CoV-2, they do pose public health threats and should be targeted by disease control interventions. A recent Comment in The Lancet Planetary Health ² called for “standardised global monitoring of water, sanitation, and hygiene (WASH) conditions” in such markets. Monitoring is one thing, but the way forward to sustainable change does not lie with standardised interventions in isolation.

As shown with the response to the threat of avian influenza virus (AIV), local context and detailed understandings are crucial in effective responses.³ Novel disinfection programmes, separating poultry species, and limiting the length of poultry stay successfully reduced AIV prevalence in the specific political circumstances of Hong Kong live bird markets. Yet, the transfer of those interventions to other lower income and quite different political settings was less effective. Although WHO guidelines⁴ recommended desirable practices in food markets and their promotion through awareness and education programmes, an evaluation of these interventions did not find substantial changes.⁵ Our and others' recent studies in Bangladesh revealed that there was no difference in the prevalence of AIVs in poultry⁶ or in the practices of workers for food markets that had or had not benefitted from UN-funded biosecurity-upgrading programmes. The needs of retailers and butchers to assure income in the immediate term and show confidence to consumers about their stock, as well as long standing practices of workers, all contributed to risky behaviours. Together, these factors resulted in low uptake of personal protective equipment, disinfection programmes, and desirable poultry management practices. Similar observations were made on backyard farms.⁷

Of course, hand washing, toilet facilities, and water supplies are important parts of the response, but perhaps not the most important parts. Behaviour change can only be enforced through regulation if national and local social, cultural, and financial factors—the social and economic structures constraining behaviours—are understood and addressed. If this is not done, interventions will probably fail. The key to the problem lies in structural interventions that are informed by detailed knowledge of local situations, of what is happening on the ground—however wet and slippery that ground may be!

Zoonotic disease emergence and transmission will not be stopped by one-size-fits-all interventions across a diverse range of settings and, in any given setting, across a diverse range of actors. Beliefs and practices along poultry trading networks are heterogeneous.⁸ The paths and transaction nodes whereby hazards become risks are also diverse. Even in a single market, large-scale slaughterers on the edge of a wet market might do business differently, work within different financial structures, and have a different perception of risk compared with somebody in a small booth with slow throughput. Actors behave in relation to their position in the trading structures and consequently have distinct sociocultural perspectives on risk, depending on the contexts in which they experience it.8, 9, 10 People's risk calculations have to be understood within those contexts: people's social interactions, how they make sense of their situation, and how these reflect the convergence of constraints and individuals' aspirations.⁸ That this is the case should be at the forefront of thought when considering how to mitigate the zoonotic disease risk generated by wet markets.

Policy homogeneity is certainly cheaper and often politically appealing in the short term. The question of whether it is cost-effective or merely cheap is something to be borne in mind when developing policy. Heterogeneity, localism, and consultation might be more expensive, but are also more cost-effective in both the short and longer term.