Quantitative analyses on the global coronavirus pandemic

Author: William Ku Page 1 of 8

Pre-Thanksgiving Dip in COVID-19 Cases

COVID-19 cases in the USA have shown a sharp decrease over the last 8 days causing the 7-day rolling average to peak and rollover (see figure below – red squares).  The question is whether this is measuring a real lasting phenomenon – perhaps attributable to local COVID-19 fires burning out, or to mitigation factors taking hold, or to some temporary factor associated with the Thanksgiving holiday.  The answer is probably a combination of all three that will ultimately be overwhelmed by an increase in Thanksgiving transmission.

Some COVID-19 outbreaks have burned so strongly and for so long (3-4 months) that local “herd immunity” may be acting as a retardant to the fire.  For example, in North Dakota (ND) 10.3% of the population has now been confirmed infected (see table below). 

StateConfirmedTestingEst. PopDeathsDeath perFatality
 Infection %Positive %Infection % million
ND          10.3                23          47          920            1,207            1.2
SD            9.0                24          44          943            1,066            1.2
IA            7.2                19          27       2,400               761            1.0
WI            6.6                15          20       3,307               568            0.9
NE            6.5                17          22          989               511            0.8
UT            6.0                  9          11          868               271            0.4
USA            4.2                  7          15  273,077               825            2.0

Given their low testing rate and associated high positivity rate near 23%, the true underlying infection rate could be 5X to 10X higher than reported (higher positivity rates correspond to a higher hidden population of infectees). This means that ND could have passed the “herd immunity” threshold of 60%-70% estimated by most epidemiologists.  South Dakota (SD) is not far behind at 9.0% confirmed with 24% positivity rate.  Six US states (ND, SD, IA, WI, NE, UT) are already above 6% confirmed infection rate and could be approaching the herd immunity threshold in a few months.  Four of these states (ND, SD, IA, NE) has refused to impose any kind of statewide mitigation measures and avoided testing and thus have a high hidden population of infectees.  Hundreds of counties in the USA could be approaching this threshold.  These states and counties could well reach herd immunity before vaccines become widely available in March.  By then it would be too late for vaccines to save lives already irretrievably lost. 

Letting the virus run wild has come at a great price for the Dakotas.  Both states have now joined the unenviable 0.1% club, that is more than a thousand deaths per million population reached by 10 USA states and only 3 countries in the world: Belgium, San Marino, and Peru.  (For reference the USA as a whole is at #10 in the world with 825 deaths per million.  The USA as a whole is far from herd immunity with just 4.2% of the population confirmed infected and an estimated 15%-20% as the true underlying infection rate.) 

Part of the reason for the recent topping of case counts could be due to the wide range of mitigation measures many counties and states have undertaken recently to flatten the curve and deal with the overwhelming demand for healthcare services (current hospitalizations are 56% higher than ever before in the USA).  These measures include mask mandates (which we view as the cheapest mitigation measure), limitations on assembly, curfews, and business/activity shutdowns.  Many of them could take several weeks to cut transmission and to manifest themselves in the data.  Moreover, many of them are not mandatory and depend on widely varying voluntary compliance.  Given the wide spectrum of responses, it will take some time to sort out which has been effective and which have not.

Finally, part of the reason for the recent dip in cases could also be just a matter of timing.  Many young adults including college students got tested for COVID-19 in the days before Thanksgiving, hoping to get negative results and a pass to go home (see graph above).  This raised the number of tests conducted to a record high of 1.98 million tests in the USA on Nov 21st.  91% of these tests came back negative and gave millions “pass” to travel.  Over the last 8 days, the number of tests dropped to 1.28 million on Nov 29th – much of it due to many Americans taking long weekends off for Thanksgiving.  We expect reported tests, cases, hospitalizations, and deaths to increase again soon. 

The incoming Biden administration must take charge of the pandemic war immediately.  We are forecasting that an additional 74.5k Americans will die over the next 4 weeks due to cases and hospitalization already in the pipeline.  Moreover, every day’s delay over the next 51 days will add 2k-3k to the death toll (this mean >100k lives irretrievably lost before Inauguration Day and vaccine public availability) – an avoidable and unforgivably tragic chapter in American history. 

COVID-19 Survival Rates Have Improved?

Amidst the bad news of COVID-19 increasing in the USA for the third time to record levels, there is some evidence that the case fatality rate (CFR = deaths/cases) has improved significantly from spring to summer.  Two large studies of patients in NYC and in England both show significant improvement in survival rates.  We have done a study of cases in Florida and find a similar trend in improvement. 

The figure above shows that cases (brown squares) in Florida first increased in March and then eased in June, only to surge again and burn out by early October.  Since then cases have risen again for the third time and deaths (blue diamonds) appear to have bottomed out and are increasing again.  During the first wave, the first 82,719 cases reported in FL on 6/17/20 were responsible for most of the 3702 cumulative deaths reported on 7/4/20.  This corresponded to an overall CFR of 4.5% (with deaths lagging cases by 2-3 weeks.  The second wave ended roughly on 10/20/20 with 676k more cases which lead to 13.8k more deaths that were mostly reported by 11/14/20.  This corresponds to an overall CFR of 2.0%, roughly a factor of 2 improvement from spring to summer.  The lag time between cases and deaths (as the reported date shown above) increased to 3-4 weeks as reporting lags increased in Florida (real lag time remains about 2-3 weeks). Notice that the scale on the right for deaths is 2% of the scale on the left for cases.  This is what we are predicting for the CFR for the third wave in FL.  A similar pattern is seen in the data for the USA as a whole where the CFR has improved from 6.7% to 1.5% currently. 

The strongest driver of CFR is age and the second wave was caused by many younger adults increasing their activity and getting infected.  We need to check how much a younger median age played into this observed improvement. 

The figure above shows that the improvement from wave 1 to wave 2 is remarkably similar for all age groups.  For example for adults between the ages of 65-74, 12.7% died in the first wave while only 5.5% died in the second wave.  Much of this improvement can be attributed to wider testing (identifying milder cases and cases earlier in their cycle), better hospital practices (e.g. proning rather than immediate ventilating), and better therapeutics (remdesivir and dexamethasone).  A newly approved monoclonal antibody, bamlanivimab, could improve this further. 

One note of caution is that FL and the USA are just approaching the low CFR levels seen in South Korea and other best-in-class countries all along suggesting that much of the improvement is due to the UK and USA finally getting their act together in terms of testing and treatment.  In the spring, USA and UK undertested and missed many asymptomatic and mildly symptomatic cases, and many hospitals were overwhelmed so only the most seriously ill were admitted who then died at a high rate.  Some of the improvements in survival rates could be reversed if hospitals become overwhelmed with equipment and staff shortages in this ferocious third wave. 

COVID-19 Cases in the USA are Rising for the Third Time

The total number of COVID-19 cases in the USA surpassed ten million or 3% of the population today.  The third wave of the Pandemic in the USA is here and it looks extremely dangerous.  For the first time, the number of confirmed cases per week has reached 700,000 or more than 100,000 per day – 50% higher than the peak of the summer wave reached in July (see brown squares in the figure below).  Cases are rising everywhere this time around in contrast to the first wave which was concentrated in the Northeast and the second wave that was concentrated in the Sunbelt. 

This third wave differs significantly from the first and modestly from the second in other ways.  Testing now is much more thorough than the first wave and slightly better than the second wave thus identifying more asymptomatic and mildly symptomatic cases than before (see figure below).  More kids and young adults are being tested now increasing the percentage of silent carriers.  

But the new cases are not all benign as new hospitalizations, albeit with a longer lag time and lower hospitalization ratio have risen steadily since 9/20 (see blue diamonds in the first figure above).  During the first wave patients were so sick they were hospitalized within a few days of diagnosis.  During the second wave, the lag time increased to about a week and those requiring hospitalization decreased by half.  The lag time now appears to be 2 weeks.  Given the rapid increase in case counts, we are forecasting that hospitalizations (currently near 55,000) will exceed the previous peaks of 60,000 by next week and set new records that will stress many hospital systems just a week or two before Thanksgiving. 

Even though hospitals are better prepared this time around with PPE, ventilators, improved treatment techniques (proning), and better therapeutics (Remdesivir, dexamethasone, and monoclonal antibodies), they could still be stressed and cause death rates to exceed those reached this past summer and challenge the horrific levels reached this past spring.  Better medicine plus wider testing and lower median ages had reduced the hospitalization ratio and improved the case fatality rate (CFR) from near 7% to 1.6%. But these favorable factors may be offset by new stresses on the healthcare system.  Deaths rates have already been creeping up since bottoming near 720 per day on 10/17 to near 950 per day (see blue diamonds in the figure below).  We are forecasting that the death rate will double to 1,440 per day by month-end.  The news could get substantially worse if nothing is done immediately.     

Now that the election has passed, the USA must depoliticize the war against COVID-19 and work together to flatten the curve to save lives.  To avoid the worst-case scenarios, pandemic fatigued individuals must agree to wear masks, social distance, and wash hands as recommended by the CDC.  The government must increase testing availability and turnaround times, improve contact tracing, and set up selective quarantining facilities to monitor and reduce community spread.  The Federal government must coordinate equipment acquisition and distribution to ensure no shortages occur this time around.  The next 74 days are crucial if we want to ensure that the case count does not more than double with another 10 million cases and the death count does not increase by more than another 160,000 Americans. 

COVID-19 Cases in Florida are Rising for the Third Time

COVID-19 cases are increasing around the world, in the USA, and in Florida.  In Florida, cases have been rising for the last 5 weeks albeit at a slower rate than many northern states as temperatures have cooled and activities have moved indoors slowly in the Sunshine State.  In Florida, the push to reopen the economy and especially schools have exacerbated the problem.  Since schools have reopened in August it is clear that kids can get infected and high school kids are as likely to get infected as the general population (see graph below). 

College kids and young adults are nearly twice as likely to get infected since they are more mobile and are less risk-averse in general.  While younger kids appear to be less contagious than older kids, their infection rates have been going up with the general population and for kids of elementary school age (5 – 10) it is now about 45% that of the average population.  Even though kids (<18 yrs old) are unlikely to die from COVID-19 (in fact none have died in the last month), a significant portion does get sick.  107 out of 10.7k kids (<18), or 1.0%, have been hospitalized in the last month.  69 FL kids (<18) have been diagnosed with multisystem inflammatory syndrome for children (MIS-C) so far this year.  Perhaps more concerning is that the asymptomatic or mildly symptomatic cases go on to silently infect others (parents, grandparents, and teachers) – increasing the hospitalization and death toll in the community.  We are beginning to see this in the recent increase in the median age of those infected from a low of 35 years old touched at the beginning of September to 39 recently (see figure below).  A similar transfer from young to old occurred this past summer and led to a record surge in deaths.   

This shift to the older generation has resulted in a 24% increase in currently hospitalized from a low of 2,005 reached 10/18 to 2,489 on 11/4 (see figure below).   

Death counts are currently near a 4-month low near 40 cases per day (see figure below).  However, the increased case counts and hospitalizations have led us to forecast death counts will increase soon for the third time this year.   All this happening before the start of the truly cold weather season bode ill for Florida in the coming months. 

The White House will not Control the Pandemic

The US government’s response to the novel coronavirus has been poor from day one.  And now Mark Meadows, the White House Chief of Staff says the federal government has given up trying to control the Pandemic.  This admission of defeat is highly irresponsible and borders on the criminal.  Governments are elected to serve and protect the people and when they fail to do their number one job, they should be voted out.  

The President and his national security advisors knew in early January, and the President understood the seriousness of the novel coronavirus by late January – way before the public or other government officials knew. 

(1)  Even if he did not want to panic the public, he should have convened a meeting of federal officials, governors, and top local officials secretly and warned them about the coming crisis.  A Manhattan Project for the Pandemic should have been set up in January to help the USA deal with this crisis.  He downplayed the virus. 

(2)  The President should have invoked DPA (Defense Procurement Act – which he eventually did 6-8 weeks later) and made sure that the USA was prepared in terms of testing, contact tracing, quarantine facilities, hospital beds, masks, and other PPE (Personal Protective Equipment).  The governors did not have this power and had to bid against one another for PPE.  Kushner should not have dropped his committee work to develop more sources for PPE.  Masking should have never developed into a political issue if there were no shortages.

(3)  When the President found out that the CDC was poorly prepared to do testing he should have accepted Germany’s offer of a PCR test in January or bought ones from South Korea to supplement our short supply.  Governors were not allowed to bypass the Federal government restrictions until mid-March. To this day Trump has an irrational ambivalence to testing.  Testing and measuring is a bedrock concept in science, medicine, and even in business.  You cannot fix a problem if you don’t measure and understand the full scope of the problem.  Ignoring it does not make it magically go away. 

(4)  The President should not have politicized CDC recommendations regarding closing and reopening businesses.  Governors and local officials should decide when to shutdown/reopen businesses and facilities.  But national health guidelines should be available and consulted to avoided patchwork and ineffective responses and confusion.  Metro-NYC pandemic cannot be managed by a single governor.  When states run out of hospital beds, equipment and doctors and nurses, governors often have just the difficult choice to shut down the state or put patients out on the street.  Uniform, unbiased health guidance would help in making this difficult decision.

(5)  Uniform and equitable policy regarding testing, manufacturing, and distribution of vaccines and therapeutics are still lacking.  Governors have to beg for Remdesivir (or Regeneron antibodies) with Trump inserting himself to play favorites – ridiculous and dangerous repeat of PPE shortage fiasco.     

The USA has done orders of magnitude worse in this Pandemic than Taiwan, Japan, or South Korea so we know the Pandemic can be controlled.  On many COVID-19 measures, the USA ranks in the top-10 worst country in the world when it should be ranked the best.  225,000 (or 300,000 if you count excess deaths) Americans need not have died.  The sad thing is the USA is not much better prepared for this third attempt at controlling the Pandemic – 10 months after the first case appeared in the USA – 10 months after President Trump knew that this was a deadly disease and a serious national problem. 

The Beginnings of a Third Wave

Last month we were concerned that the leveling off of new daily cases in Florida and the USA was only temporary.  Over the last four weeks of steadily increasing daily case counts (see red squares in the figure below), we are increasingly concerned that we are seeing the beginnings of the third wave as temperatures cool and indoor activities resume in northern USA (Wisconsin is especially bad now).  We are also concerned that the pressures to reopen schools for in-person learning, reopen the economy before Election Day, and the increasing numbers of maskless, crowded rallies are exacerbating the normal seasonal rise in cases. 

Some of the increasing cases could be due to improved testing.  After stalling for 2 months testing has improved as schools and businesses reopen and want to keep ahead of increased infections by increasing testing.  This has again picked up an increasing number of asymptomatic and mildly symptomatic cases.  If this were the only reason for the recent increase in cases hospitalizations and death counts would not increase. 

In fact, after bottoming in mid-September, the number of currently hospitalized with COVID-19 in the USA has been rising for the last two weeks (see blue diamonds in the figure below).  As we had pointed out before this is a leading indicator of a future rise in death counts. 

Death counts are currently stuck near 750 per day (blue diamonds in the first figure above) but will rise again right near Election Day – lagging rising cases by 2 to 4 weeks.  This is not a good harbinger for President Trump’s re-election chances.  We had suggested that he ease off on maskless, crowded rallies in September to improve his chances of reducing the death count by November but he had chosen to forge ahead with large risky superspeader events such as the Rose Garden announcement for Amy Barrett in defiance of scientific advice.  Impatience bought him a second wave in June; impatience will have now bought him a third wave. 

President Trump’s COVID-19

President Trump announced that he tested positive for COVDI-19 on October 1st.  Since then at least seven other attendees of a Rose Garden ceremony for Amy Barrett on September 26th have tested positive for the virus.  We wish them all speedy and full recoveries.  However, the prognosis for each of them varies widely depending on their age, gender, and general health. 

The exponential age and gender behavior of COVID-19 patients has remained roughly the same since we first published our version of the graphic below 6 months ago.  Improved testing and identification of asymptomatic and mildly symptomatic cases mostly among younger adults have improved the overall case fatality rate (CFR = deaths/cases), but have not changed the strong exponential age dependence.  Better healthcare treatments in terms of logistics (avoiding bed, equipment, and supply shortages that plagued Italy early on) and the introduction of newer therapeutics such as Remdesivirsteroids, and clonal antibodies have prolonged patient lives and improved survival rates modestly. 

For example, a 50-yrs old female with average health, like the First Lady, would have a CFR of 0.7%.  On the other hand a 74-yrs old male with average health would have a CFR of 13%.  The President, being somewhat overweight with moderately high cholesterol and blood pressure issues would have a worse CFR – perhaps 30 times worse than for his wife.  For a 31-yrs old female of average health like Hope Hicks, her CFR is less than 0.1% similar to that for seasonal flu.  So the range of possible outcomes is extremely wide. 

Hospitalization is a leading indicator of the severity of the disease.  In Florida about a third of all hospitalized COVID-19 patients eventually die.  The risk of hospitalization for the very obese nearly triples that for a person with normal weight.  Currently the President and Chris Christy (with asthma and obesity) are both hospitalized.  

Schools Continue to Spread COVID-19

A couple of weeks ago we pointed out that schools have become the new breeding ground for COVID-19.  More data have allowed us to understand the problem a little better.  While people of all ages can get infected with the novel coronavirus, it seems that the younger the person, the less likely they are to get infected or die from the disease.  Deducing the real underlying susceptibility to the novel coronavirus is not easy given that the measured infection rate depends on how mobile each group is, how compliant each group of people is with mask-wearing, social distancing, and personal hygiene, and how thoroughly each age group is tested for the virus.  With all grades of K-12 back at school or online at roughly the same time in Florida, those in elementary, middle, and high school are 37%, 47%, and 72% as likely as the average Floridian to get infected, respectively.  Teens in high school (14-17 yrs old) have been trending higher while younger children’s infection rate has remained more stable.  Younger children appear to have stronger immune systems than older teens and young adults that protect them against getting infected, and if infected, they seem to put up a stronger fight against the virus.  

Older teens and young adults going to colleges and universities (18-24 yrs old) appeared to have a modestly greater susceptibility than the average Floridian to the novel coronavirus until the last week in August.  Since college reopened and some athletics have restarted, this age group has become nearly three times as susceptible to the novel coronavirus.  We do not believe that they are intrinsically three times more likely to contract the disease, but their increased mobility and their riskier lifestyle choices make them more attractive vectors for the novel coronavirus. 

If schools and universities that have reopened do a good job of testing, contact tracing, and selective isolation of new cases, they should not pose incremental risks to the general population.  However, if they follow the same pattern as we have observed earlier this summer when young adults frequented bars and restaurants and then went home and transmitted the disease to their parents and grandparents, they could start a third wave of new infections. 

Schools are New Hot Spots for COVID-19

Many students have been back to school for a month now and we are seeing new outbreaks of COVID-19 cases among young people in Florida and throughout the USA.  Fortunately, the June to August resurgence of COVID-19 cases among the general population has eased so that the overall case counts in Florida have not increased yet.  As we had pointed out before COVID-19 is far less deadly for children and young adults but their rates of infection may not be all that different.  From the graph below, children younger than 15 seem to be less likely to get infected but since many have been staying home until recently, and as a group they were thought to be less vulnerable and tend to be under-tested,  Thus it is not clear yet what their true infection rate is.  The age group with the highest infection rate is young adults 25-34 who have been most socially active and were largely responsible for the summer surge in deaths as they went to bars and beaches and transmitted the disease to older adults. 

The summer age transfer can be seen in the graph below.  The median age of new cases in Florida decreased from 44 years old in the spring to 33 in late June, and increased back to near 44 in August as the disease spread throughout the state.  Recently as schools reopened and students became more mobile, the median age in Florida has dipped to near 36 years old. 

Schools at all levels of K-12 grades have encountered increased infections as they opened classrooms and campuses to children.  Young kids can get the disease and transmit it but below the age of 14, they seem to be only half as infectious as the general population (infections could be undercounted due to under testing).  Within K-12 ages middle school kids seem more susceptible than elementary school kids but the statistical significance is not very high.  High school kids 14-17 years old appear to be 70% more likely to get COVID-19 than elementary school kids, 5-10 years old.  More detailed data by school district would help us understand the underlying school reopening issues better. 

Young adults aged 15-24 have been tracking higher than the general population all summer even with schools closed, but as colleges reopened in Florida in late August, the infection rate for this age group suddenly increased more than the general population.  This population segment contributes 27% of all new cases in Florida even though it has only 12% of the population.  The pandemic in the USA could be reignited as colleges are pushed to resume in-person classes and large scale contact activities such as football.  Some colleges are well prepared in terms of testing, contact tracing, and selective isolation but many others are not.  If and when they are overwhelmed and send students home or off campus for remote learning, the risk of community transmission could rise.  The median age of new cases after dipping in September could rise again in October as students infect older adults in Florida and the rest of the USA. 

Until the community where the school is located has its outbreaks under control, schools, especially colleges, should reopen remotely.  If colleges chose to reopen for in-person classes, they must exercise extreme care and follow guidelines recommended by this unreleased CDC document.  Unless they do so, reopening can blow up and put the local community and the country at risk. 

Will Florida and USA See Another Surge in COVID-19 cases this Fall?

Daily COVID-19 new cases, hospitalizations, and deaths have been falling for several weeks in Florida along with that for the USA as a whole.  The pandemic in the USA has not burned out and many states in the Midwest are experiencing flare ups.  In Florida, the daily new case count after falling for 6 weeks has just flattened out this week at a level 5 times higher than in May when Florida first tried to reopen (see figure below).  

This has not deterred the governor from doing his second COVID-19 victory tour and encouraging counties to resume reopening, nursing homes to accept visitors, residents to celebrate Labor Day, and schools to reopen for physical classes and team sports. Will an early victory dance and complacency encourage the virus to surge again this fall in Florida and the USA?  

The governor is betting that kids can go to school safely because they are less likely to get infected than adults.  We have shown that this is not true especially given the rebellious nature of teenagers.  A further assumption is that when they do get infected few will die from it.  This is true although the corollary that they will not suffer severe long term health damage is probably not true.  While only 0.02% of kids 17 and under die from COVID-19, 1.2% of these young people do require hospitalization.  Finally, the assumption that child-to-adult transmission is less likely than adult-to-child transmission is controversial

The data show that children can and are getting more infected throughout the country as schools reopen.  In Florida, the earlier resurgence saw thousands of young adults get infected as they celebrated in bars and attended other large gatherings.  The median age of new cases dropped to 33 in June from 45 in April (see figure below).  

As the younger adults transmitted the disease to older adults at home and in the community, the median age increased back to near 44 in August. Now we are seeing the pattern repeat as kids go back to school.  In the first 5 days of September more than a thousand school-age kids in Florida have been infected along with hundreds of college students.  What is not clear yet is whether these younger kids going home to generally younger parents and grandparents will transmit as seriously as the young adults did in earlier.  We are betting that while it will not be as bad it will nevertheless contribute to a second resurgence in hospitalizations and deaths.  Thus we may never experience a real respite from the pandemic as a potential true second wave comes along with seasonal flu this winter.  

A second resurgence or a third peak is still avoidable.  As long as people continue to wear masks, and practice social distancing and good hygiene, the virus spread can be mitigated.  Governments and institutions such as colleges and businesses need to provide easily accessible and timely testing as well as effective contact tracing and selective isolation facilities.  However, if the government claims victory too early again, and continues to send mixed messages about masking, social distancing, and testing, the odds are on the virus’s side. 

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