Pandemic Prevention

How do you prevent a pandemic?

The reactive approach: ‘Wait and respond’

Unfortunately, as evidenced by COVID-19, the dominant strategy for preventing pandemics is to wait for a disease outbreak to occur, then rush in to respond. You identify the pathogen and its source, find out who’s infected and how the disease spreads, and then contain the spread through various control measures (e.g. contact tracing, quarantine, vaccination, etc). This typical ‘wait and respond‘ approach can be effective, but nevertheless it is reactive, and can therefore only be deployed once a disease has begun to circulate in the human population and may also fail due to delayed response time or accelerated spread.

A pandemic control ‘response’ must be enacted quickly in outbreak situations in order to be effective, and there are many factors that can delay an appropriate response. Perhaps the symptoms of the disease are nearly identical to the flu, so no one even suspects that a different disease has emerged; perhaps the disease is transmitted by those who show no symptoms (asymptomatic individuals), making it difficult to track and contain disease spread; perhaps the disease is novel, so there are no diagnostic tests, treatments, or vaccinations in place to aid in a response; or perhaps the disease taps into our global network of commercial air travel, spreading far and wide before much can be done. There are many factors that can hamper effective disease control, and unfortunately (as we have seen with SARS-CoV-2), sometimes our actions are too little, too late, and we fail to prevent a pandemic.

So is that the end of the story? Are we stuck with this reactive response, forced to always be on the defensive, just waiting for the next disaster to strike? Or is there another way to prevent pandemics?

Knowing where to look

Over the last several decades, scientists have become increasingly confident about where the next pandemic is likely to come from. We know that more than half of all infectious diseases affecting humans (60%) result from pathogens we share with wild and domestic animals, and that 75% of emerging zoonotic diseases (those diseases transmitted from animals to humans) are attributed to pathogens with origins in wildlife reservoirs (1,2). We also know that certain groups of wildlife (bats, rodents, non-human primates, and birds) are the most likely sources of potentially-dangerous pathogens, and we know that increasing human-wildlife interactions, land-use change, and other ecological factors can promote transmission of zoonotic pathogens to humans (3,4). So whereas in the past, we’ve been caught flat-footed against pathogens because we didn’t know where the next threat was lurking, we can now focus our efforts to stop diseases at their source. While we may never know exactly where or when the next threat will emerge, there is much we can do to narrow our search, promote early detection, and reduce the chances of a novel emerging disease becoming the next pandemic.

The preemptive approach: How EcoHealth Alliance and the WAB-Net are working to prevent pandemics like SARS-CoV-2

EcoHealth Alliance and the Western Asia Bat Research Network (WAB-Net), adopt a ‘proactive’ approach to pandemic prevention. With a focus on bat-origin zoonoses, WAB-Net aims to identify zoonotic viruses before they find us, identify risk factors that may facilitate spillover into humans, and collaborate with experts across Western Asia to improve the region’s ability to prevent and mitigate disease outbreaks.

Put in more formal and specific terms, the WAB-Net research project aims to:

• Characterize the diversity of bat coronaviruses (CoVs) in Western Asia through non-lethal biosurveillance of bats
• Understand the risk factors associated with spillover of these viruses into humans
• Establish cross-discipline, cross-country partnerships, dedicated to improving biosecurity, biosafety, and bat conservation throughout the region

The current SARS-CoV-2 outbreak has demonstrated the devastating effects that an emerging coronavirus can have, in terms of mortality, morbidity, and economic impacts. This pandemic has shown, now more than ever, the importance of stopping viruses at their source. From what we know, SARS-CoV-2 (the virus causing COVID-19 disease) is a bat-origin virus, (although an unknown intermediate host, not a bat, could potentially have been involved in the spillover to people). The closest known relative of SARS-CoV-2 found in nature was from a Rhinolophus affinis bat in Southwest China (5,6). As with most emerging zoonotic diseases, the virus likely emerged due to human-driven factors — including the thriving wildlife trade and live animal markets. The rapid spread of SARS-CoV-2 from one country to the next is also a salient reminder that viruses do not respect national borders. All of these aspects of the SARS-CoV-2 pandemic highlight the importance of having a regional zoonotic disease network like WAB-Net in place — one that works across nations to facilitate communication, share information, and improve regional capacity to find viruses before they find us.

Our network’s non-lethal sampling of bats is expanding our knowledge of bat viral diversity and our ability to identify (and reduce) high-risk behaviors more likely to lead to disease spillover. Viral sequence data from pre-emergent pathogens can be used to prioritize viruses for future research and ultimately can be leveraged to develop broadly effective vaccines and antiviral drugs that are protective against a wide range of viruses. Our study of human-bat interfaces recognizes that viral emergence is most often the result of human behavior, not the fault of bats or other wildlife. Our network of regional and global bat research experts is committed to bat conservation and ensuring that bats are not blamed or persecuted. Regional networks like WAB-Net can also play a role in routine biosurveillance efforts, in which people, livestock, and wildlife are frequently tested for evidence of viral spillover. All of these efforts aim to prevent and detect viral spillover, so that potentially dangerous pathogens are stopped at their source.

The more we understand about bat viral diversity in Western Asia, as well as the risk factors associated with viral spillover in the region, the better able we are to prevent, mitigate, and respond to devastating outbreaks like SARS-CoV-2, as well as the pandemics that have yet to come. Rather than wait for the next outbreak to strike, WAB-Net is taking a proactive approach to disease prevention, and working towards building a safer world without pandemics.

(1) Taylor LH, Latham SM, Woolhouse MEJ. (2001). Risk factors for human disease emergence. Philos Trans R Soc Lond B Biol Sci 356: 983–8; (2) Karesh WB, Dobson A, Lloyd-Smith JO, Lubroth J, Dixon MA, Bennett M, Aldrich S, Harrington T, Formenty P, Loh EH, Machalaba CC, Thomas MJ, Heymann DL (2012). Ecology of zoonoses: natural and unnatural histories. The Lancet 380 (9857), 1936-1945; (3) Allen T, Murray KA, Zambrana-Torrelio C, Morse SS, Rondinini C, Di Marco M, Breit N, Olival KJ, Daszak P (2017). Global hotspots and correlates of emerging zoonotic diseases. Nature Communications 8, 1124 (2017). https://doi.org/10.1038/s41467-017-00923-8; (4) Olival KJ, Hosseini PR, Zambrana-Torrelio C, Ross N, Bogich TL, Daszak P (2017). Host and viral traits predict zoonotic spillover from mammals. Nature 646–650 (2017). https://doi.org/10.1038/nature22975; (5) Zhou P, Yang X, Wang X, Hu B, et al. (2020). A pneumonia outbreak associated with a new coronavirus of probable bat origin. Nature 579, 270–273; (6) Latinne A, Hu B, Olival KJ, Zhu G, Zhang L, Li H, Chmura AA, Field HE, Zambrana-Torellio C, Epstein JH, Li B, Zhang W, Wang L-F, Shi Z, Daszak P (2020). Origin and cross-species transmission of bat coronaviruses in China. Nat Commun 11, 4235 https://doi.org/10.1038/s41467-020-17687-3.