The dynamics of disease transmission

The dynamics of disease transmission


Infections diseases were supposed to have disappeared by the end of last century according to the surgeon general last century. And it was reasonably optimistic because we were just starting to have streamline public health policies, improved hygiene around the world, and vaccines and drugs. and we thought we could continue along that line and by the end of the century be pretty much safe against any emerging pathogen. And it turns out that up to this day we only eradicated just one human pathogen. So it’s this very powerful force of nature that actually has shaped human history. And one key process that governs if an epidemic will become an epidemic, or if an epidemic will become a pandemic is transmission. And fluids shape transmission. Fluids are everywhere and pathogens are always in fluids. After the SARS epidemic hit it was midpoint during my PhD, I realized that I really wanted to move into an area where I could have an impact on public health. And coming from fluid dynamics what I realized is that there were critical processes that we really did not understand that well. the focus was still on these static description of isolated drops being emitted from coughing, sneezing, talking, etc. that is rooted in works of Wells from the 1930’s. Now, what we found in our earlier research is that these drops are not coming out isolated. It’s a cloud that’s coming out. A cloud of gas that is turbulent, high-energy, and carrying them much further than this one and two meter rule that has been applied up to now. And another very important aspect is that his cloud dynamic completely changes the persistence of the drops in terms of distances, timescales, heights of where these drops can go and be sucked into the ventilation system. You can also start thinking about why some individuals spread more than others, what are these properties that can make them be more efficient spreaders? Another example of how fluids and health come together is for food safety and agriculture. And there, we have looked at the process of rain-induced disease transmission and so when drops basically hit leaves that are contaminated there is an empirically known process of transmission that occurs in the field. But that also occurs in nature, of course, in the wild. But up to now, that was also a black box. Like for transmission between humans the transmission through the splash process that was pretty much conjectured. And that’s something that now is leading to additional research where we’re looking at other aspects of food safety. So the pipeline of fundamental research and rigorous research to elucidate how things work so that we know we were not just lucky to discover a pattern but we understand it so well that when we turn the knobs, we control that pattern. With an increasing population world-wide, an increase in connectivity and increase of drug-resistance of pathogens that we understand we are at high risk by mid-point of this century of going back to a pre-antibiotic, pre-vaccine era as a global population. So my job – besides doing research, teaching, and trying to mentor these bright minds – is to raise this awareness, and bring it to the attention of the policy-makers, and the decision-makers at the global scale in terms of global health, and in terms of also revisiting our current recommendations and regulations about transmission.