Agreed that the 3-log reduction is appropriate for cases where the “baseline” dose is pretty low. Our team is still uncertain about what protection level might be needed, but has some high-level reasons to expect that background environment-to-human (E2H) aerosol pathogen concentrations are likely low in many environments.
One reason is that airborne microbial concentrations and species composition vary a lot across environments. Existing microbial ecosystems also tend to be quite diverse, so even the most common bacterial species often make up only a small share of total bacteria. Likewise, an E2H pathogen, such as a mirror bacterium, probably wouldn’t become highly concentrated across most natural ecosystems. While mirror bacteria might not face the same predation pressures as many other bacteria, they would still have to compete for resources and wouldn’t necessarily occupy a large share of many ecological niches. So even though outdoor air can contain thousands to millions of bacteria per cubic meter, mirror bacteria probably wouldn’t be present at high concentrations in many outdoor environments. To the extent concentrations vary substantially by location, there might also be places with much lower exposure risk.
There are also reasons to expect that the infectious dose wouldn’t necessarily be one bacterium. Even if human immune systems did not respond to mirror bacteria, our respiratory tracts have physical defenses, such as blocking or clearing inhaled particles, and bacteria do not automatically colonize every environment they land in. The BPP team is very unsure what an infectious dose might be, and it could be low—for infections like Q fever and TB, I think the infectious dose is quite low—but it is not guaranteed to be low for E2H pathogens.
Last, the 3-log reduction is what our team currently thinks could buy humanity enough run room to find better solutions, such as building better protections or developing and mass-producing medical countermeasures (MCMs). So the 3-log protection doesn’t need to provide perfect protection for someone’s whole life, but might just keep people alive for a year or a few years. Also, in the early stages of an E2H pathogen release, while humanity is increasing resilience through better protection options or MCMs, concentrations might still be lower as the pathogen spreads, so the threshold for useful protection might be lower.
Agreed that the 3-log reduction is appropriate for cases where the “baseline” dose is pretty low. Our team is still uncertain about what protection level might be needed, but has some high-level reasons to expect that background environment-to-human (E2H) aerosol pathogen concentrations are likely low in many environments.
One reason is that airborne microbial concentrations and species composition vary a lot across environments. Existing microbial ecosystems also tend to be quite diverse, so even the most common bacterial species often make up only a small share of total bacteria. Likewise, an E2H pathogen, such as a mirror bacterium, probably wouldn’t become highly concentrated across most natural ecosystems. While mirror bacteria might not face the same predation pressures as many other bacteria, they would still have to compete for resources and wouldn’t necessarily occupy a large share of many ecological niches. So even though outdoor air can contain thousands to millions of bacteria per cubic meter, mirror bacteria probably wouldn’t be present at high concentrations in many outdoor environments. To the extent concentrations vary substantially by location, there might also be places with much lower exposure risk.
There are also reasons to expect that the infectious dose wouldn’t necessarily be one bacterium. Even if human immune systems did not respond to mirror bacteria, our respiratory tracts have physical defenses, such as blocking or clearing inhaled particles, and bacteria do not automatically colonize every environment they land in. The BPP team is very unsure what an infectious dose might be, and it could be low—for infections like Q fever and TB, I think the infectious dose is quite low—but it is not guaranteed to be low for E2H pathogens.
Last, the 3-log reduction is what our team currently thinks could buy humanity enough run room to find better solutions, such as building better protections or developing and mass-producing medical countermeasures (MCMs). So the 3-log protection doesn’t need to provide perfect protection for someone’s whole life, but might just keep people alive for a year or a few years. Also, in the early stages of an E2H pathogen release, while humanity is increasing resilience through better protection options or MCMs, concentrations might still be lower as the pathogen spreads, so the threshold for useful protection might be lower.