Quantitative analyses on the global coronavirus pandemic

Month: July 2020

Has Miami Solved the COVID-19 Problem?

Ever since the first case of COVID-19 was identified in Miami on March 11th and the first death recorded on March 27th, the number of cases and deaths have increased steadily in Miami-Dade County.  On March 24th, when total case count neared 500, parts of Miami-Dade began to lockdown with most of South Florida locked down by March 30th.  The lockdowns effectively flattened the curve within weeks.  After peaking with an average of 400 new cases per day in mid-April, the number of cases dropped slowly to near 150 per day, Miami-Dade reopened on May 18th.  As it turned out this level of infection was not sufficiently low enough to safely reopen and soon after Memorial Day new cases began to surge again along with the rest of Florida. 

The daily new cases for Miami-Dade (brown squares) track that of the rest of Florida (blue diamonds) very well at about 25%.  Over the last 12 days the 7-day rolling average case number for the rest of Florida has peaked while that for Miami-Dade has continued to rise, albeit at a slower pace.  What is surprising is that the Miami-Dade death count has deviated even more dramatically over the last 10 days – downward rather than up. 

This suggests that the case fatality rate (CFR = deaths/cases) for Miami-Dade has all of a sudden improved dramatically for Miami-Dade versus the rest of Florida.  It is not clear to us why this should be the case.  The strongest driver of CFR is age, and the median age of cases in Miami and the rest of Florida had dropped in June as more young adults ventured out and partied with poor masking or social distancing.  However, the median age has crept back up for both Miami and the rest of Florida over the last 5 weeks.  Other comorbidities and demographic factors do not appear to have changed significantly from spring to summer to justify this improvement in CFR for Miami. 

So either Miami is vastly undercounting their COVID-19 hospitalizations and deaths recently due to abnormally high volume constraints, or they have found a miracle therapeutic that vastly improves survival rates from a May peak of 8% (=16/200) to 0.6% (=15/2600) now.  We are estimating that the true CFR for Miami-Dade is 1.4%, lower than May’s 8% due to wider testing of asymptomatic and mildly symptomatic cases, younger patients, and better therapeutics, but higher than 0.6%.  Death counts will catch up to this estimate over the next few weeks. Moreover, unless Miami-Dade reverses much of its reopening steps to mitigate the spread, both cases and deaths could continue to rise.  Note that the total case count is now 200 times higher than when it last decided to lock down Miami-Dade.    

Small Steps in the Right Direction

After nearly 3 months of downplaying and ignoring the Pandemic, the President has finally taken a few positive steps towards mitigating the spread of COVID-19.  He is now strongly recommending the use of facial coverings.  While this is not the same as a national mandate for masks that we recommend it is a step in the right direction.  He still needs to reinstate some of the original guidelines for social distancing that expired April 30th.  On the testing front, he seems to have shifted from saying the US should stop testing so much to saying that testing has allowed the US to show much better case fatality rate (CFR = deaths/cases) trends.  This is the same argument we had advanced in May to try to convince the President to test more.  The US needs to increase testing capacity to reduce turnaround times from more than a week currently to less than a day and to drive the positivity rate (percent positive test results) below the 5% level recommended by the WHO (see figure below).  The government should not cut funding for additional testing capacity.  Otherwise, contact tracing and targeted isolation programs would be extremely expensive and probably ineffective. 

Hopefully, the President will take more aggressive actions once he recognizes how serious the Pandemic has become in the USA.  Testing has turned up more asymptomatic and mildly symptomatic cases but it has also revealed real widespread community infections in the majority of states.  A look at the trend in the number of Americans currently hospitalized in the USA shows that the favorable downward trend from mid-April to mid-June reversed and is now near the 60,000 highs set in mid-April.  .   

This shows that while the resurgence in daily case counts hit young adults first as they emerged recklessly from lockdown in May, the virus has spread now to older adults.  In Florida, the median age of new cases that fell to 33yrs a month ago is now at 42yrs old – equal to the median age of Florida’s population.  The figure below shows our near term forecast for deaths due to COVID-19 in the USA.  Due to more testing, the CFR will be reduced from near 7% at its peak this Spring to below 3% this Summer but since the number of cases has now more than doubled, the total death count may be just as high.  This means that the Summer outbreak could be as bad as the Spring outbreak.  With no additional mitigation steps taken, we are now forecasting 9 million cases and 260,000 deaths in the USA by Election Day, November 3rd

Masking and Social Distancing Will Slow Pandemic

Wearing a mask – a public health tool – has been politicized in the USA.  It is unfortunate because many countries have shown that masking and social distancing can work to slow the spread and severity of a pandemic.  In the USA, the three largest states, California (CA), Texas (TX), and Florida (FL) have all experienced a significant resurgence in COVID-19 cases for the last 6 weeks since the end of May (see figure below).  Each of them has seen record new highs in daily case counts and deaths.  However, their reaction to the resurgence has been different and their recent experience and prognosis going forward will be very different.

California as the largest state in the USA had the highest level of cases per capita in May as they expanded testing and picked up more asymptomatic and mild cases.  When infections exploded in June, Governor Newsom reacted the earliest and mandated mask-wearing across the state on June 19th.  Subsequently, he ordered bars in 7 counties to close and in a series of increasingly stringent steps, CA is now closing indoor businesses serving about 80% of the population.  Many counties (Los Angeles, San Diego, and San Francisco for example) have decided not to reopen physical schools in the Fall because they do not believe they could be opened safely.  These rational mitigation steps have all helped CA slow the exponential growth in cases to become now the lowest of the top three states in daily cases. 

Mitigation stepsCA DateTX DateFL Date
Mandate mask19-Jun2-Jul
Close drinking in bars28-Jun26-Jun26-Jun
Closing indoor businesses 60%1-Jul
Closing indoor businesses for 80%13-Jul
Not reopening schoolsLA, SD, SF

By comparison, Texas has been more reluctant to shut down the state, although recently Governor Abbott has threatened that if individuals and businesses do not help to slow the outbreak he may be left with no choice.  In the meantime, he did mandate the usage of masks statewide on July 2nd.

Florida’s Governor DeSantis has been the slowest to face reality.  Against all evidence, he insists that the recent resurgence is due to wider testing of young adults and is nothing to worry about.  At the state level, the only action taken to date is the closing of indoor bar drinking.  At the city and county level, many mayors have taken stronger mitigation steps but without quick and decisive action at the state level, the virus will continue to rage in FL with cases per capita soaring from the lowest in May to the highest among the top three states now. 

The prognosis is for worse to come to Florida.  The following figure shows the hospitalization rate (7-day rolling averages) for the top three states.  For both Texas and California, the daily net hospitalization (new admissions minus discharges) show that they have peaked and are on a downward trend. The daily hospitalization rate for Florida is still rising – reaching a new record of 458 admissions, yesterday.  This does not bode well for Florida. 

Widespread mask-wearing can mitigate the spread of the virus as both CA and TX have shown.  And if everyone also practiced social distancing consistently, it will slow the virus substantially.  If individuals do not do this voluntarily, the government has to step in as they have done in CA and mandate safe behavior.  Having done so, California is showing early signs of bending the curve and controlling the latest virus outbreak. 

COVID-19 Setting Death Records in Florida

For six weeks COVID-19 cases have been surging in Florida but the governor has insisted that it was not a problem because Florida was testing more and revealing more mild and asymptomatic cases.  Then when the percentage of positive results started to rise 5 weeks ago from 4% toward 20% recently, he conceded that community spread is occurring but it was mostly among younger adults who will not require hospitalization or stress Florida’s health care system.  When hospital usage started to surge 3 weeks ago, he claimed that Florida has plenty of hospital beds and very few people will die.  Now, this week, death counts have been rising and setting new 7-day rolling average highs every day (see figure below).  He is still resisting healthcare experts’ calls for instituting more mitigation measures ranging from mandating mask usage to rolling back reopening steps, to statewide lockdown.  Even Texas Governor Abbott has conceded that a lockdown is possible if the virus continues to grow unchecked.   

What are the prospects for the next couple of months for Florida?  The rise in deaths this week results from widespread flouting of CDC guidance for masking and social distancing beginning 6 weeks ago on Memorial Day weekend.  That led to the surge in confirmed cases 5 weeks ago.  Deaths now appear to lag diagnosis by about 4 weeks due to the availability of widespread testing (however testing delays now will probably shorten this lag time back to 3 weeks).  So we already know that death counts will continue to rise for the rest of July (see dashed line in the figure above) due to all of the diagnosed patients in the pipeline: hospitals, ICUs, and ventilator users.  The case fatality rate (CFR = deaths/cases) in July will be lower than it was in the spring due to the lower average age of infectees, dropping from above 4% to below 2%.  However, this positive trend may have reversed:  the age distribution of new cases that had dropped the median age of new cases from 45yrs old to 33yrs old 3 weeks ago is now 40yrs old (the detailed age distribution published by Florida for new cases looks exactly like that for existing cases).  This reflects the fact that young adults who got infected in bars and beaches go home and interact with parents and grandparents and transmit the disease to them.  So based on what has already occurred, FL death count will at least double that recorded this past Spring.   

What will happen to Florida’s confirm case count for the rest of this month and August?  To gain an insight into this question we had looked at the similarity between the current outbreak in FL compared to the earlier outbreak in New York (NY) 3 months ago.  The figure below shows that Florida’s outbreak has tracked NY’s remarkably well except that FL started at a higher base infection level. 

The other major difference is that early along NY’s exponential outbreak, the NY governor (along with the governors of NJ and CT) imposed a statewide lockdown on March 23rd.  Three weeks later NY’s outbreak topped out and started to improve and get under control.  Florida is now near that NY top but will FL break its fever naturally as some lockdown skeptics have suggested?  We find no reason to be optimistic.  While certain cities and countries in Florida have imposed mandatory mask-wearing and rolled back the reopening of bars, indoor dining, beaches, etc.  the state as a whole has not.  Moreover, some counties are continuing to reopen further against the advice of health experts.  Disney World reopened today, and MSL and NBA and AAU Volleyball are restarting this month in Orlando.  The Republican Convention is still scheduled for Jacksonville next month.  All of these actions will exacerbate rather than mitigate the spread of the pandemic.   If the governor really feels that reopening K-12 schools in August is important for the welfare of the children and their parents, it is imperative that the state government takes strong action now to mitigate the rise in cases so that schools can reopen safely.  

COVID-19 Cases and Deaths are Both Surging in California

It looks like the surge in COVID-19 cases in California (CA) has not ended yet.  While cases are no longer making remarkable new highs, the 7-day rolling averages (solid blue line against the left axis in the figure below) are still increasing – reaching a new high of 8,242 (recent data are a little bit distorted by Los Angeles County restatement of data).  The imposition of statewide masking on June 18th should have kicked in this week. But spotty compliance may not be sufficient to stop the surge.  On July 1st, the governor also shut all bars, indoor restaurants, and movie theatres for 70% of the most infected population which should bite in a couple of weeks.  If not, additional rollback of reopening steps may be required. 

In the meantime, death counts (brown line showing 7-day rolling average against the right axis) have started to rise after a 2-3 week lag toward a new high and reached a single-day high of 150 deaths.  Death counts will continue to rise for the rest of July (green triangles against the right axis), but there are some signs that recent mitigation steps are helping.  Wider testing has lowered the case fatality rate (deaths/cases) from near 4% in mid-April to near 2% now.  

The percentage of tests returning positive results are still rising – hitting a new high of 11.7% today.  This indicates that the virus is still spreading throughout the state.  However, the number of net new hospitalizations (admissions minus discharges) has topped out near 200 per day (205 today).  This suggests that the majority of the 8,000 new cases are mostly asymptomatic or mild.

More optimistically the net new ICU usage has started to decline and actually went negative today at -8.  This suggests that the rise in death counts may not last too long.  This outlook is much brighter than the current experience in Arizona, Texas, and Florida.   So a somewhat mixed picture but there are some reasons to be optimistic that the recent mitigation actions taken by the governor will help California control this pandemic a second time if everyone contributes by masking, social distancing, and washing hands. 

COVID-19 Deaths Are Rising in Texas

Many people are questioning the seriousness of the resurgence in COVID-19 cases in the USA in June.  They look at the death count per day in the USA as a whole and see it continuing to go down into July.  Why is the media blowing this out of proportion?  Why are the scientists so worried when death counts are continuing to fall?  According to the President and most governors, the new cases are all due to superior USA testing.  Unfortunately, this is not true in Texas and most of the other states in the USA.  If the virus reproduction rate was stable and not growing exponentially, the percentage of tests returning positive (shown as 7-day rolling average in the graph below) would go down or remain roughly constant.  However, it has clearly risen over the month of June from near 6% to near 14% (17.6% as of 7/6). 

This means that the virus is growing again in Texas after it reopened on May 1st.  Before Texas met all the gating criteria for Phase 2, it opened further on May 18th.  That and Memorial Day Weekend crowds not masking or social distancing let the virus run rampant in June.  The figure below shows the number of daily confirmed cases (blue diamonds against the left axis) soaring from near 1,000 at the end of May to above 8,000 today. 

Daily net hospitalization (admissions minus discharges), normally near zero throughout most of April and May soared to 517 on 7/6 (7-day rolling averages are shown in the graph below).  This has caused many hospitals throughout Texas to become overstressed, especially those in Houston.  Texas does not publish ICU or ventilator data so it is not possible to fully track the progression of patients through the hospital system.  But cases are already turning into deaths 2-3 weeks after the beginning of the surge.  In the figure above, death counts per day (brown squares against right axis) that had been tracking downward throughout May and into June started turning up in mid-June.  The good news is that Texas’ case fatality rate (CFR) that had always been relatively low due to the low median age of its population (34.8yrs) has improved as wider testing has turned up milder and asymptomatic cases in mostly younger adults.  CFR that had been above 3% in early May is now tracking slightly below 1% (note that the right axis is 1% of the left axis).  Hospitals and doctors know how to treat COVID patients better now with improved therapeutics and procedures.  However, if the hospitals do get overloaded this optimistic scenario may not play out well. 

The governor has finally rolled back some reopening steps and mandated the use of face masks but he needs to roll the reopening back further until the state’s testing, contact tracing, and selective isolation procedures can catch up with the resurgence in infections and not overstress the hospitals. 

Those Who Cannot Learn From History Are Doomed to Repeat It — or Worse

COVID-19 cases have surged in Florida (FL) to historic levels but it is a pattern that we have seen before in the USA 3 months ago and in many other countries such as China and Italy several weeks before that.  Somehow many governments failed to recognize the exponential growth pattern of an outbreak and stop it in time before it did substantial damage.  This time around for Florida to repeat the same devastating mistakes would be truly sinful.  Florida experienced an outbreak in March and luckily escaped it relatively unscathed due to the timely action of certain mayors and county officials to lockdown their local businesses before the outbreaks got serious.  They could have avoided general lockdowns if they had the testing, contact tracing, and selective isolation capacity in place.   However, since no one in the USA prepared in January and February, the only alternative was to use a blunt instrument like a general lockdown to suppress the outbreak.  Second time around, there is really no excuse not to be prepared.  Three-months further along, we should have built up the testing, contact tracing, and isolation capacity to deal with any resurgence but it doesn’t look like we are any better prepared this time around.

The figure above shows the daily confirmed COVID-19 cases reported in Florida (brown squares) over the last 11 weeks.  Florida was averaging 800 cases per day even as it expanded testing from 10,000 to 30,000 per day from mid-April to early June.  Florida was able to drive its positivity rate (percent of tests returning positive) down from 12% to near 2.7% allowing it to reopen safely in early May.  A month later FL decided to go to phase 2on 6/5 even though signs of trouble were already brewing as test capacity stalled and the positivity rate rose above 4% near the end of May.  This mistake became more evident as the month wore on and the number of daily confirmed cases surged to a series of record highs.  The 7-day moving average of cases (solid brown curve) is now near 8,000 – ten times higher than the base rate just a month ago corresponding to a doubling time of 9 days.  Where is it likely to go? 

The figure above also plots the New York (NY – blue diamonds) experience shifted by 91 days or 3 months earlier.  The middle of the curve with the exponential growth matches eerily well.  Will we follow the NY curve and top out in a week?  That would be the optimistic scenario but not the likely scenario.  By 6/21 Florida should have locked down the whole state as NY did on 3/23 (along with its neighbors New Jersey and Connecticut).  At a minimum, FL should have rolled its reopening back phase 1.  The fact that the governor has reacted minimally so far (prohibited the sale of alcohol at bars) does not bode well for Florida.  While certain counties such as Miami-Dade, Broward, and Palm Beach have resisted moving to phase 2 and required mask-wearing now, this may not be enough to stop the outbreak in the rest of the state.  In fact, Florida is in a far worse situation than NY because NY really only had one serious outbreak in metro-NYC whereas, in Florida, the infection is everywhere: metro-Miami, metro-Tampa, metro-Orlando, metro-Jacksonville and nearly every city and county in the state.  What is required now is a statewide mandate for masking and social distancing.  It requires that the state rollback reopening to Phase 1 until adequate testing, contact tracing, and selective isolation can be put into place.  Additionally, FL needs to postpone the reopening of DisneyWorld scheduled for 7/11, and the reopening of sports (MLSMLBNBA) that have been planned and that is sure to exacerbate the outbreak.  Otherwise, the exponential growth phase of the Florida outbreak could continue to surge well past the worst seen in NY.   

COVID-19 Hospitalizations Are Rising in the USA

COVID-19 cases have surged in the majority of states in the USA over the last two weeks.  Many governors claim that the surge in cases is mostly due to expanded testing.  A detailed look at the data shows that while some of the increase in case counts is due to expanded testing the majority is not.  The number of tests performed increased throughout April and May in the USA to near 600,000 tests per day, but have not been able to keep up with the surge in newly confirmed cases in June as states reopened too quickly, and individuals failed to follow masking and social distancing guidelines.  The graph below shows that for the largest 3 states, California (CA), Texas (TX), and Florida (FL), the percent of Polymerase Chain Reaction (PCR) tests returning positive results (plotted as 7-day moving averages) have increased in CA to 6%, and surged to historic and alarmingly high levels near 16% in TX and FL. 

More importantly, the number of hospital admissions have risen dramatically in June as well.  Florida does not report the number of patients currently in hospitals, but only the cumulative total of hospital admissions for COVID-19.  From this data, we can calculate the number of new hospital admissions each day.  This number has risen from a low of 100 per day in early June to a recent 7-day average of 178 per day.  At this rate, many hospitals in FL are approaching full occupancy. TX and CA do report the number of patients currently occupying hospital beds.  This allows us to calculate the net number of hospital admits (new admits minus discharges) per day.  Over the last two weeks, this statistic has increased from a stable level near zero (admissions equal to discharges) to near full capacity in many TX hospitals and even a few CA hospitals.  This is not a good sign for governors who are pushing the theory that most of the new cases are young adults who are only mildly symptomatic and do not require much healthcare resources. 

To truly understand how seriously ill the newly admitted patients are we need to have an accurate census of ICU beds.  Unfortunately, states such as TX and FL do not track this consistently or accurately or have chosen to suppress such data.  In CA, this data is tracked and it is not pretty.  For an 8 week period from the end of April to mid-June ICU admits balanced discharges and ICU occupancy level was stable.  Since 6/16 it has gone up steadily over the last two weeks.  This does not bode well for other states. 

Diagnosis leads to hospitalizations, leads to ICU usage, leads to deaths 2-3 weeks later.  Death counts have begun to rise in TX and we forecast will soon rise in FL and CA as well.  All of this foretells a tragic summer for the USA.  The governors of some of the most infected states such as Arizona, California, and Texas are finally taking action to halt and in some cases to reverse reopening steps until their testing, contact tracing and selective isolation could catch up with this latest surge.  Hopefully, this will flatten the curve again, but it is also incumbent upon individuals to exercise more vigilance in terms of masking, social distancing, and washing hands appropriately. 

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