What We Don’t Know About SARS-CoV-2 and COVID-19

SARS-CoV-2 is a new virus in the human ecosystem. Humans didn’t pay much attention to it when it was only in bats. It’s of great interest to humans now. Because it’s new to our bodies and societies, we know nothing about it. We are picking up empirical observations quickly, but it’s hard to put them together in real time, motivated by sickness and death.

Research is proceeding, particularly for testing methods for both the virus and human immunity to it, for a vaccine, and for treatments. Many questions are still open. We will hear bits and pieces from the research, but the bigger questions won’t be answered for some time. Read More

Criteria For Loosening Restrictions

Last week, President Donald Trump decided that the country must open back up. He issued a slide package about requirements for opening things back up. The next day, he issued three “LIBERATE” tweets, naming specific states. The purpose of those tweets seems to have been to encourage demonstrations against distancing provisions issued by those governors.

The demonstrations themselves seem to be centrally directed rather than spontaneous, and financially supported by the right-wing money machine. Read More

The Two Numbers I Am Watching Before Things Open Up

The best case would be R < 1 and herd immunity >70%.

R is the reproduction number, the number of cases that one case causes. R0 is the basic reproduction number, which is an idealization of how a disease spreads in a given population. Reff is a measured number for a particular situation. In looking at the models, I see R0 being used in ways that look like it contains other parameters as well. So I will just use R, which is the same as Reff. Using it without a subscript and the context will, I hope, indicate that it is totally situational. Read More

Looking At Data

The mathematical models are not the only way to make sense of the progress of the pandemic. Raw numbers can tell us a lot too. This is my favorite “how are we doing” set of charts. They can display active cases, confirmed cases, new cases/day, deaths, deaths/day, and recovered, for countries or US states and territories, in linear or log scale, raw or normalized for population. And now they have data by counties, too.  Sometimes I just take a quick look, other times, I look for a specific place or parameter, or just more detail. The data come from the Johns Hopkins coronavirus project. Read More

The IHME Epidemiological Model

There’s some uproar this week because the estimates provided by the model apparently most used by the Trump administration have been revised significantly downward.  I’m not clear on exactly what was done, but a revision is not entirely surprising.

Let me give some background on modeling generally and the model that the administration seems to be using. I say “seems to be using” because the White House task force has not been clear about what model is being used.

The model whose results have changed is the IHME model (Institute for Health Metrics and Evaluation University of Washington).  seems to be the primary model used by the White House response team. However, the figures President Donald Trump repeated in briefings last week of as many as 2.2 million deaths are the same as given by the Imperial College model. Dr. Deborah Birx has mentioned both the IHME model and what seems to be an internal model. Read More

What Do The Models Say About What Happens Next?

We are now isolating ourselves, at least the non-MAGA portion of the population. The numbers of cases of Covid-19 – and deaths – are mounting. What can we expect? What happens next?

Lots of us are wondering what comes next in the SARS-CoV-2 pandemic. We already have an indication in New York City. At the same time, many states and countries are instituting lockdown measures that should decrease the numbers of sick and dead. I’ll use the Imperial College paper to discuss what is likely to come next. Read More