Infectious diseasesMonitoring the emergence of infectious diseases

Zoonotic diseases that pass from animal to human are an international public health problem regardless of location — being infected with Campylobacter from eating undercooked chicken in the U.K. is not uncommon, for example — but in lower-income countries the opportunities for such pathogens to enter the food chain are amplified.

Professor Stephen Baker from Oxford University’s Center for Tropical Medicine and Global Health, Nuffield Department of Medicine, says that where he currently works in Vietnam, and across the region, humans have a very different way of interacting with animals being bred for food than would be familiar to those in the United Kingdom. If one were to travel to the Mekong Delta region (in the south of Vietnam) it would not be uncommon to see people who keep a large variety of farm animals in, or in close proximity to, their houses. It comes as little surprise that in a country where raw pig blood and pig uterus are commonly consumed, the number one cause of bacterial meningitis is Streptococcus suis, a colonizing bacterium of pigs.

The major problem of researching emerging infections is predicting how they arise and how we respond to them once they do.

Given the complexity of zoonotic disease emergence and transmission, it is very rare that an outbreak can be traced back to the first identified human or animal case — known as the “index case” — and this remains a substantial challenge. A lack of effective health and surveillance infrastructures in many lower income countries compounds this issue, as we are wholly reliant on individuals entering the healthcare system and getting diagnosed, which seldom happens.

The ideal scenario is that we can identify new pathogens with zoonotic potential in animals prior to them spilling over into humans. However, if we cannot achieve this we need to be aware of their existence and be able to respond by treating people effectively once they are infected. This means rapidly identifying patients with a particular infection, assessing the severity of their condition and diagnosing the agent. Therefore, having sentinel hospitals with well-trained clinical staff, good diagnostics and microbiology facilities is the best opportunity we are going to have to detect diseases.

The most recent example of this is a case of Trypanosoma evansi infection – a protozoan disease of animals and, rarely, humans – that we identified in a woman attending our hospital with an atypical disease presentation. Ultimately, we