Top news, reports and insights for today:
- Daily COVID-19 headlines for Saturday:
- White House blocks Dr. Fauci scheduled testimony calling it “counterproductive” for the nation’s top infectious disease expert to speak to congress (The Guardian)
- University of Pennsylvania says Dogs may be able to detect coronavirus (Washington Post)
- Number 2 official at the CDC issues report saying U.S. was too slow in testing and travel restrictions (Forbes)
- U.S. deaths fall, cases rise as states reopen
- Epidemic control measures worked in China, a look at R0
Dr. Thomas Inglesby wrote a very informative paper in JAMA today reminding us of a recent study that showed dramatic changes over time in the value of R0 in China.
First a quick review. You have probably heard people talk about R0, also known as the basic rate of reproduction. This is a measure of how infectious a pathogen is. It’s a really important number if you want to understand and stop an outbreak. R0 is the expected number of secondary infectious cases produced by a primary infectious case. Knowing how many other people will be sickened by each infected person tells us a great deal about how far and fast an outbreak can spread. As a rule of thumb, an outbreak with an R0 greater than 1 will continue to propagate via ongoing cycles of transmission. How far above 1 tells us how far and fast it will spread. R0 of 2 or more means exponential growth of new cases. The goal of epidemic control is to lower this number to below 1.0 so the outbreak will burn out. That means the actual value of R0 will be high initially before the outbreak is identified, and control measures like social distancing and testing are put into place. As those measures come on line, we expect this number to fall. How far and fast it falls is a good measure of how well you are doing at addressing the epidemic. So, during an outbreak, it is important to measure the rate of reproduction and how it changes over time. That number we call the effective reproduction number, or Rt (read: R-Sub-T).
Pan and colleagues published this very compelling figure in their April 10 paper showing just how potent the outbreak control measures were in China. In the first 3 weeks of January, before control measures were initiated, the Rt in Wuhan ranged from 2.5 to 4; the epidemic had exploded in Hubei Province. Then, after lockdowns, traffic suspension, and home quarantine, the Rt plummeted to below 1 by early February. Additional control measures have kept the disease in check since then.
What this means? The big take-home message is that outbreak control measures work. China effectively suppressed an outbreak in a matter of weeks, driving the Rt down below 1 using potent measures, many of which seem draconian to us in the West. China, a nation of 1.44 billion people, now reports 3 deaths and 58 cases per 1 million population (compared to over 200 deaths and 3,500 cases per million in the U.S.). We can not and should not do everything that China has done, but the story in China is a warning to the U.S. about what might lie ahead as we now move to suspend those control measures that have mitigated the pandemic in the U.S. to this point.
- New Zealand is stopping COVID-19 with strict control measures, offering a model to the world
The National Geographic has a story today about the success story in the island nation of New Zealand, home to 4.8 million people. We haven’t heard much about New Zealand since the early days of the pandemic. That’s because they have done an amazing job of arresting the spread of the disease. They now rank 53rd among nations in cases per million population. They have reported less than 1,500 cases in total and 20 deaths (according to Worldometer). They have tested more than 30,000 per 1 million, 30% more than the U.S.. I used Aatish Bhatia’s site to generate the figure below. What’s really impressive is that things looked pretty bad for New Zealand in the beginning. Then, at around 900 total cases, we see the telltale downward hook that shows an abrupt end of exponential growth. We see this in other Southeast Asian nations, especially China, but New Zealand and South Korea are developed, democratic open societies, where the harsh measures employed by China and Hong Kong were not implementable. That doesn’t mean they weren’t strict. New Zealand locked it’s borders tight and instituted mandatory quarantine for all visitors. Then came a complete nationwide lockdown with domestic travel moratorium, restricted vehicle traffic and some of the strictest measures of any country. They did this when they had a handful of cases. The prime minister, Jacinda Ardern, makes regular statements to the nation, explaining her policies and why they are being taken. She relies of a team of scientists and public health experts in crafting the response. Now, they are seeing 20 new cases per week. The U.S. has 200,000. If only we could all be Kiwis.