I’ve mentioned a number of times that we really don’t know the precise mix of factors that are making some states and countries disasters and allowing others to keep it in check. A critical component in all cases is where communities and governments are taking mitigation and containment seriously. But in New York, are we just doing a great job or is the initial outbreak – in which at least 20% of the city population was apparently infected – giving us some extra ability to keep case rates down?
New York City isn’t close to herd immunity by traditional definitions. But ‘herd immunity’ isn’t a binary thing – you don’t have it and then suddenly you do. It’s more like a friction that builds up incrementally in the process of community spread as more people cease to be capable of being vectors because they have immunity to the disease. The more people become infected the more friction there is until at one point the virus can’t effectually reproduce itself and fizzles out.
Clearly this factor is helping New York keep cases very low. But how much – whether it is a minor assist or a major factor – we don’t know.
That’s where a very interesting article from David Wallace-Wells comes in.