Month: September 2020

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. 

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. 

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.