Why has COVID-19 largely spared California so far?

Victor Davis Hanson, of the Hoover Institution at Stanford, is a rather unorthodox conservative thinker and pundit.  He is a scholar who used to write about such unusual topics as the virtue of being self-sufficient and working with one's hands, whether that means doing one's own car repair or planting grape vines.  Until President Trump was elected, I used to find him an interesting read.  Unfortunately, he now strikes me as largely "in the bag" for the president.

But this article in National Review isn't about Trump (at least not explicitly - see the end of the post for a thought on that).  His point of departure is that the COVID-19 rhetoric coming from California's governor, Gavin Newsom, and the mayor of Los Angeles, Eric Garcetti, has been extremely pessimistic.

According to Hanson, Newsom has predicted that something like 25 million Californians would be infected by the virus, with perhaps as many as a half million deaths in the state.  This is accompanied by the predictions, familiar to all of us in all states, that medical facilities would be overwhelmed.

But - so far - it hasn't happened.  Here is Hanson:

Yet a number of California’s top doctors, epidemiologists, statisticians, and biophysicists — including Stanford’s John Ioannides, Michael Levitt, Eran Bendavid, and Jay Bhattacharya — have expressed some skepticism about the bleak models predicting that we are on the verge of a statewide or even national lethal pandemic of biblical proportions.
The skeptics may be right. As of this moment, California’s cumulative fatalities attributed to coronavirus are somewhere over 140 deaths, in a state of 40 million. ...

In contrast, as of Monday morning, New York State, with about half of California’s population, has about eight to nine times the number of deaths, and 20 times the per capita rate, at 60 deaths per million residents. In fact, California has a much lower per capita death rate than many of the nation’s largest states; for that matter, its per capita death rate is similar to that of nations that so far have mysteriously escaped the virus’s modeled wrath. Currently, California has lost fewer than 4 people per million, roughly between South Korea’s 3 deaths per million and Germany’s 5, which are both being studied as outliers. Of course, statistics change hourly, but for now California’s data remain mysteries.

Hanson goes on to note a number of factors that would seem to suggest that California should be at least as vulnerable as the country as a whole:

• The state doesn't usually do so well in avoiding infections: typically it has the most flu cases each year, ranking in the middle in per-capita flu infections.  It also has a high number of residents who are diabetic or pre-diabetic, which have been identified as risk factors for the Coronavirus
• Prior to the imposition of the flight ban from China, thousands of Chinese travelers flew into California airports every day.  Several California airports had regular direct flights from Wuhan, including during the time period earlier this year when the epidemic was spreading in that Chinese city.  Hanson reports that nearly 1 million Chinese visitors flew into California from October thru February.  And once the flight ban was imposed, thousands of Chinese nationals have been stranded in California without a way to return home
• California's demographics seem to work against it, with 8 million Californians living below the poverty line and over 150,000 persons experiencing homelessness
• California's rank among states is average to poor in such per-capita health care metrics as hospital beds, number of doctors and number of nurses
• The state has the most residents for whom English is not the first language, which would pose a challenge for public health communication

Yet despite all these factors working against it, California is doing relatively well - so far.  Hanson then goes on to ask why, and considers some possible explanations:

• Reporting challenges: It may be that it is difficult for such a large and diverse state to consolidate and report test results and deaths - it may be that the virus has been doing its work, but that work simply hasn't been reported yet.  In addition, Hanson notes that many infected patients who die also have other health conditions, and suggests that there may be inconsistency in assigning causes of death to patients infected with the virus
• The climate factor: California's climate is warmer than those of most states (although not Louisiana, which has been hit very hard), which may lend some credence to the notion that the virus doesn't do as well in warm weather.  Hanson notes that the weather in California in March has been chilly and rainy, and so the evidence is ambiguous for the climate explanation 
• Early shelter-in-place order: California adopted a statewide shelter-in-place order early (beginning March 19) - although some other states did so at roughly the same time: by March 23, such hard-hit states as New York, Louisiana, Washington and Illinois also had shelter-in-place policies
• Dispersed population: California's population density is lower than the hardest-hit areas like New York City and New Orleans; but Hanson notes that districts in San Francisco and LA are comparable to New York's density

Hanson also spends some time exploring some alternative theories to the prevailing medical and public health wisdom - for example, the possibility that the virus began spreading and infecting the population considerably earlier than the first months of this year, so that some sectors of the population (including in California) may already have developed a sort of herd immunity.  I am not ready to lend much credence to these theories, which Hanson also describes as minority views and heterodox.

Also - it's worth noting that, at least in my opinion, Hanson has been the opposite of critical of President Trump; and some of these non-mainstream theories lend aid and comfort to the president's evident wish to minimize the impact of the virus, presumably so that we can get back to a normal life as soon as possible before the fall elections.

Nevertheless, Hanson's piece leaves one with the sense that there is still much that is not well-understood about the virus - there are still mysteries to be explained.  In the meantime, all we can do is the best that we can - and in my view, that means following the advice of our leading public health experts.