Wednesday, March 18, 2020

Don't count on corona virus being seasonal

A lot of people are pinning their hopes on the corona virus being seasonal and magically going away during the summer like the flu.  Don't bet on it.  Brazil, where has hot and humid summer-like conditions year-round, saw its first case of corona virus on February 25.  Since then they have been on the same exponential growth curve as the rest of the world.

Our only realistic hope for keeping this from spreading to everyone in the country (and a concomitant death toll in the millions) is to dramatically ramp up our testing capacity.  You can't fight an enemy that you can't see.  We are badly behind the curve on this thanks to the Trump administration being asleep at the switch (to say nothing of active denial) about this for so long.  Make no mistake, this virus is nasty.  It's not the flu.  Yes, it's still true that there are fewer cases of COVID-19 than there are annual deaths from the flu, but that probably won't be true for much longer.  Summer might bring a miracle, but the numbers from Brazil do not look promising.  This is probably going to get a lot worse before it gets better.  It will eventually get better, but it will take months or years, not weeks.  We need a better plan than shelter-in-place.


Publius said...

Wearing a Coat Doesn't Help

Common cold viruses are primarily a winter affliction because:
* Rhinoviruses replicate more robustly at lower temperatures.
* Your nasal cavity temperature is 2 - 4 °C cooler than your core.
* Lower nasal cavity temperatures also lead the cells lining it to release fewer immune system signaling molecules, resulting in less efficient antiviral defense response of infected cells at cool temperature.
* Humidity is also important (and has a strong link to temperature). Cold weather usually brings with it lower relative humidity. Heating of homes typically lowers the relative humidity, unless the homeowner is aggressively using a humidifier.

In addition, you have:
* School is in session, an efficient environment to pass cold infections
* Sick relatives show up at winter holiday parties

Overview article in Medical News Today

The overview article also points to lower Vitamin D levels in winter, due to less sunshine. See Vitamin D and the Immune System

A Decrease in Temperature and Humidity Precedes Human Rhinovirus Infections in a Cold Climate

Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells

Temperature dependence in human Rhinovirus infection of human MRC-5

Cold temperature and low humidity are associated with increased occurrence of respiratory tract infections.

Roles of Humidity and Temperature in Shaping Influenza Seasonality

Information like this for COVID-19 is unavailable.

Of course, you can get the "common cold" during the summer -- and usually, they are more severe than the ones you get the winter. "Summer colds" tend to be caused by adenoviruses whereas winter colds are caused by rhinoviruses.

etbe said...

In Australia Sydney has more cases than Melbourne but is significantly warmer. Warm weather hasn't helped them.

XO said...

This post is on point. I've been telling other folks the same - this continues until we disrupt it.