One World, OneHealth

ID Transmission started 2024 by reporting on the effects of climate change on the spread of infectious disease. So, what better way to end it than by thinking about strategies to respond to those challenges?

In this interview, Paul Anantharajah Tambyah, President of the International Society for Infectious Diseases (ISID), reveals why the organization believes in a low-tech approach to disease surveillance, and a OneHealth approach to disease control.

Please tell me about the work of ISID.

Of the world’s professional societies for infectious disease, ISID is probably the largest to focus on low- and middle-income countries. Whereas some professional societies have a very strong presence in high-income regions, ISID has historically tried to hold meetings and serve those living and working in developing nations. We also target low- and middle-income countries for capacity building and for our open-access journal content. In terms of mentorship, we have an Emerging Leaders Program which targets bright young scientists and clinicians, including pathologists, from across the low- and middle-income spectrum of Africa, Asia, and Latin America. Those in the program are given the opportunity to review journal articles, participate in ISID’s Knowledge Exchange, gain experience writing content, and participate in our Congress meetings.

ISID is also responsible for the Program for Monitoring Emerging Diseases (ProMED), which is one of the few human-curated, event-based surveillance (EBS) systems in the world right now. ProMED was the first system to pick up COVID-19, on December 30, 2019 (EST). It was also the first to pick up MERS in 2012 and to raise a concern about an atypical pneumonia, in November 2002, which eventually turned out to be SARS in Southern China.

Most other surveillance systems now involve some element of AI and data analytics to mine various data sources. Some of them are very clever – looking at prescriptions, hospitalization rates, weather patterns, and so on – and churning out predictive models that suggest outbreaks of disease such as pneumonia or encephalitis.

ProMED is a bit different – it receives its data via a variety of sources that include AI-based systems as well as its own subscriber/reader base, which numbers over 40,000 public health professionals, interested laypeople, and allied industries. We have a public submission form that anyone can use if they suspect a health event. Moderators post health events – some of which are so new that the cause is unknown. Often they will issue a Request for Information (RFI) in cases where information has not been made public by governments or is not yet available, such as when diagnostic test results are still pending.

Our team of moderators and copy editors are all public health experts who use their combined years of experience to eliminate fake stories as well as weed out repetitive/recycled stories with new dates – something that is becoming more common with AI search algorithms.

What has ISID’s research revealed about the interplay between climate change and disease?

In low- and middle-income countries we have noticed a rise in cases of infections such as cholera. There has also been a marked rise in the populations of pathogenic algal blooms and bacteria in waters around heavily populated centers. Most noticeable is the spread of vector borne diseases, such as malaria. Historically that has been a lowland disease but, with rising temperatures, we have seen it spreading to altitudes that were previously too cold for mosquitoes to survive. Dengue fever is another example – we are seeing outbreaks spreading in the United States and Southern Europe for the first time, and more severe/long-lasting outbreaks across previously affected regions of the globe.

In the face of environmental and humanitarian changes, what are the biggest threats to health?

The spread of endemic diseases – those which are always present – such as tuberculosis, is largely due to overcrowding and poverty. These diseases thrive in overcrowded and poorly ventilated areas with poor sanitation and hygiene, when drug-resistant strains start to emerge. Wars and climate emergencies have caused mass migrations of people from rural to urban areas, exacerbating the health threats.

This same displacement of people also gives rise to epidemic diseases. If we look at the latest mpox emergency declared by WHO, 90 percent of the cases have been in the Democratic Republic of Congo, where war has uprooted many people from their homes and forced them into crowded spaces with terrible conditions.

What is the OneHealth approach, and how might it help protect worldwide health in the future?

The OneHealth approach tries to break down the silos between human, veterinary, plants, and environmental health. A good example of how this might be applied is with bird flu, which is raging across dairy farms in the United States, and in wildlife across much of the globe. Farmers and veterinarians are trying to figure out how the disease is spreading amongst the dairy farms. And, at the same time, experts in human health are investigating potential disease spillover from cows to humans, and poultry to humans.

So, to control the spread of bird flu, the approach must be from the animal side and the human side. It requires the clinicians and pathologists from the veterinary side to talk with those on the human health care side and decide on a coordinated approach.

If we think about the history of the H5N1 virus, it first appeared in 1996 in China, and in the early 2000s there were large outbreaks of bird flu all over Southeast Asia. Vaccines were then developed – not only human vaccines, but also bird vaccines. Countries like China, Vietnam, and France have vaccinated all their domestic poultry, with varying success, but the overall learning is that a comprehensive effort across species is needed.

The OneHealth approach would also look at mixed farms and decide how to protect pigs, cattle, and other farm animals. It relies on public health experts stepping away from their own departments and specialties, talking to other types of specialists, and looking at the bigger picture. For example, I’ve learned a huge amount about bird physiology from the ProMED community. There are big differences in water and air birds and the kinds of viruses they are susceptible to that I certainly never learned in medical school, but have picked up via the OneHealth approach.

What is pathology’s role in the OneHealth approach?

Pathology has a huge role to play. Say there are animals starting to die off – we would start collecting samples for virology and examining them with PCR or metagenomics. But identifying a virus doesn’t necessarily correlate with the cause of death or disease. You need a pathologist to tell you whether the virus is intracellular, whether it’s causing a cytopathic effect, and what tissues are being infected. And I’m a firm believer that without the pathologist’s input, the microbiologist’s input is only halfway there.

Way back when I used to attend clinical pathological conferences where we discussed the differential diagnosis for a strange and unusual case, it was always the pathologist who came in with the answer in the end…