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Much of the current discourse on — and dismissal of — the Covid-19 outbreak focuses on comparisons of the total case load and total deaths with those caused by seasonal influenza. But these comparisons can be deceiving, especially in the early stages of an exponential curve as a novel virus tears through an immunologically naïve population.

Perhaps more important is the disproportionate number of severe Covid-19 cases, many requiring hospitalization or weekslong ICU stays. What does an avalanche of uncharacteristically severe respiratory viral illness cases mean for our health care system? How much excess capacity currently exists, and how quickly could Covid-19 cases saturate and overwhelm the number of available hospital beds, face masks, and other resources?

This threat to the health care system as a whole poses the greatest challenge.

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As I initially described in a Twitter thread, simple mathematics can derive rough estimates for how this might play out.

This exercise can inform our level of urgency and equip us to anticipate non-obvious, second-order effects, some of which can be mitigated with proper preparation.

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As of March 8, about 500 cases of Covid-19 had been diagnosed in the U.S. Given the substantial underdiagnosis at present due to limitations in testing for the coronavirus, let’s say there are 2,000 current cases, a conservative starting bet.

We can expect a doubling of cases every six days, according to several epidemiological studies. Confirmed cases may appear to rise faster (or slower) in the short term as diagnostic capabilities are ramped up (or not), but this is how fast we can expect actual new cases to rise in the absence of substantial mitigation measures.

That means we are looking at about 1 million U.S. cases by the end of April; 2 million by May 7; 4 million by May 13; and so on.

As the health care system becomes saturated with cases, it will become increasingly difficult to detect, track, and contain new transmission chains. In the absence of extreme interventions like those implemented in China, this trend likely won’t slow significantly until hitting at least 1% of the population, or about 3.3 million Americans.

What does a case load of this size mean for health care system? That’s a big question, but just two facets — hospital beds and masks — can gauge how Covid-19 will affect resources.

The U.S. has about 2.8 hospital beds per 1,000 people (South Korea and Japan, two countries that have seemingly thwarted the exponential case growth trajectory, have more than 12 hospital beds per 1,000 people; even China has 4.3 per 1,000). With a population of 330 million, this is about 1 million hospital beds. At any given time, about 68% of them are occupied. That leaves about 300,000 beds available nationwide.

The majority of people with Covid-19 can be managed at home. But among 44,000 cases in China, about 15% required hospitalization and 5% ended up in critical care. In Italy, the statistics so far are even more dismal: More than half of infected individuals require hospitalization and about 10% need treatment in the ICU.

For this exercise, I’m conservatively assuming that only 10% of cases warrant hospitalization, in part because the U.S. population is younger than Italy’s, and has lower rates of smoking — which may compromise lung health and contribute to poorer prognosis — than both Italy and China. Yet the U.S. also has high rates of chronic conditions like cardiovascular disease and diabetes, which are also associated with the severity of Covid-19.

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At a 10% hospitalization rate, all hospital beds in the U.S. will be filled by about May 10. And with many patients requiring weeks of care, turnover will slow to a crawl as beds fill with Covid-19 patients.

If I’m wrong by a factor of two regarding the fraction of severe cases, that only changes the timeline of bed saturation by six days (one doubling time) in either direction. If 20% of cases require hospitalization, we run out of beds by about May 4. If only 5% of cases require it, we can make it until about May 16, and a 2.5% rate gets us to May 22.

But this presumes there is no uptick in demand for beds from non-Covid-19 causes, a dubious presumption. As the health care system becomes increasingly burdened and prescription medication shortages kick in, people with chronic conditions that are normally well-managed may find themselves slipping into states of medical distress requiring hospitalization and even intensive care. For the sake of this exercise, though, let’s assume that all other causes of hospitalization remain constant.

Let me now turn to masks. The U.S. has a national stockpile of 12 million N95 masks and 30 million surgical masks for a health care workforce of about 18 million. As Covid-19 cases saturate nearly every state and county, virtually all health care workers will be expected to wear masks. If only 6 million of them are working on any given day (certainly an underestimate) they would burn through the national N95 stockpile in two days if each worker only got one mask per day, which is neither sanitary nor pragmatic.

It’s unlikely we’d be able to ramp up domestic production or importation of new masks to keep pace with this level of demand, especially since most countries will be simultaneously experiencing the same crises and shortages.

Shortages of these two resources — beds and masks — don’t stand in isolation but compound each other’s severity. Even with full personal protective equipment, health care workers are becoming infected while treating patients with Covid-19. As masks become a scarce resource, doctors and nurses will start dropping from the workforce for weeks at a time, leading to profound staffing shortages that further compound the challenges.

The same analysis applied to thousands of medical devices, supplies, and services — from complex equipment like ventilators or extracorporeal membrane oxygenation devices to hospital staples like saline drip bags — shows how these limitations compound one another while reducing the number of options available to clinicians.

Importantly — and I cannot stress this enough — even if some of the core assumptions I’m making, like the fraction of severe cases or the number of current cases, are off even by several-fold, it changes the overall timeline only by days or weeks.

Unwarranted panic does no one any good, but neither does ill-informed complacency. It’s inappropriate to assuage the public with misleading comparisons to the seasonal flu or by assuring people that there’s “only” a 2% fatality rate. The fraction of cases that are severe really sets Covid-19 apart from more familiar respiratory illnesses, compounded by the fact that it’s whipping through a population without natural immune protection at lightning speed.

Individuals and governments seem not to be fully grasping the magnitude and near-inevitability of the national and global systemic burden we’re facing. We’re witnessing the abject refusal of many countries to adequately respond or prepare. Even if the risk of death for healthy individuals is very low, it’s insensible to mock decisions like canceling events, closing workplaces, or stocking up on prescription medications as panicked overreaction. These measures are the bare minimum we should be doing to try to shift the peak — to slow the rise in cases so health care systems are less overwhelmed.

The doubling time will naturally start to slow once a sizable fraction of the population has been infected due to the emergence of herd immunity and a dwindling susceptible population. And yes, societal measures like closing schools, implementing work-from-home policies, and canceling events may start to slow the spread before reaching infection saturation.

But considering that the scenarios described earlier — overflowing hospitals, mask shortages, infected health care workers — manifest when infections reach a mere 1% of the U.S. population, these interventions can only marginally slow the rate at which our health care system becomes swamped. They are unlikely to prevent overload altogether, at least in the absence of exceedingly swift and austere measures.

Each passing day is a missed opportunity to mitigate the wave of severe cases that we know is coming, and the lack of widespread surveillance testing is simply unacceptable. The best time to act is already in the past. The second-best time is right now.

Liz Specht is the associate director of science and technology at The Good Food Institute.

  • I love this article, and its intention, yet there are so many variables unknown! First; transfer rate? If an infected patient shakes hands with 100 other people- how many acquire the infection? Are therefore these results dumb luck? Or a natural resistance/immunity?

    Next (in no order of importance), but does survival grant immunity vs. this and potential new strains? Have we even explored re-infection rates? How many infected hands do we need to shake to reach 50% confidence of transferal?

    Additionally, as we seek to repopulate the work force, can we prove survival, and possibly therefore immunity to further infections? And at what confidence level?

    We are assuming straight up – 100% transfer – and yet, this is untrue.. yet to what degree? If i hug two positive friends- what then is my likelihood of contracting the infection? Is it .25*.25? Do these statistics change based on age? 80+ years.90*.90 vs. a 20 yr old .125*.125?

    Thank you for some baseline numbers. yet we are still too far behind the curve to truly understand!

  • Here is what I understand or believe to be true and how I am reacting. The Corona Virus is 8.2 miles from my house in Santee, CA, where my wife and I live. MCAS Miramar is where they are quarantining and repatriating international travelers, just over the hill, a 12-minute drive. The infection rate of those known with the virus is 2.8-4.2. Which means everyone who has the virus transmits it to 3-4+ people statistically. I believe this will be lower in the U.S. because other customs include touching and kissing. The virus has a suggested run rate of 2-4 weeks from contact through the onset of symptoms to non-contractible. Of the average person who gets the disease, not elderly or physically compromised, 2-6.1% averaging at 3.6% of those who contract the COVID-19 will die… this is such a variable it’s crazy to wrap my head around… age, smoking, pollution, other diseases… All of the variables involved make it hard to envision, but I’m trying to. 15-20% infected will need supervised care beyond home recuperation. That typically consists of a hospital bed. From age 40 up, the graph is what in business is called “The Hockey Stick” for the severity of symptoms and death. The elderly are severely more vulnerable.
    I use the CDC, WHO, and John Hopkins Hospital data, It’s all out there and available… I don’t use Fox, CNN, CNBC, not even NPR, etc. So that’s a snap-shot of the data I understand. This stuff is an obsessive-compulsive statisticians dream!
    We gave toilet paper, Purell, and Clorox wipes to our kids because we old folks like to stay stocked up. I guess us “hoarders” are appreciated now.
    My wife and I have started three weeks of minimal contact. We also have at least an additional four weeks of dried food if we need to shelter in place. On the other hand, thank goodness for next day delivery.
    I do know that if my wife or I get the Wuhan Coronavirus, we will most likely die. We both are elderly, disabled, and have multiple underlying physical ailments. We are not afraid. We are staying informed and pragmatic. If we get sick, we will go to the VA Hospital. In the meantime, we are binge-watching 60’s and 70’s shows (no sports is weird) and praying for everyone’s health and well being.

    • You, sir, and your wife, are awesome! As a “younger” guy in his late 40’s, I am inspired by your courage, your pragmatism, and you moxie! Thank you Jesus for people like you. Praying for your good health, Jerry

  • 36 million flu cases for the US alone in 2019 and the CDC is using a weekly estimate to get the numbers.

    Using media methodology in 2018 in the US 647,000 people were hospitalized for flu and 61,200 died with a death rate of 9.24%

    • You need to do 61,200 as a percentage of the total infected, which was between 37 – 43 million, not just the total hospitalized, so the death rate is around 0.15%.

      You should also consider that the serious complications rate of flu that year was around 1.6% of the total infected.

      The serious complications rate of COVID-19 is around 20% and the death rate is somewhere in the ballpark of 2-4%.

      It is also more contagious than the flu, with a considerably higher R0.

      If this spreads like the flu, which it will, unless drastic steps are taken to prevent that outcome, the numbers flooding hospitals and dying will massively outnumber that of even the worst flu seasons.

  • Many to most 80-90+ in the US are in assisted living, nursing homes, age in place and not all will end up in hospital ER whereas in Italy (I’m guessing) more will stay with their families, their own place, or communities that do not have the same resources – they will need to go to the hospitals sooner.

    • March 15, 2020
      I will go on record to tell you that your denial is madness.
      Deaths run ~2% of cases and happen ~4 weeks after infection
      Infections double weekly.
      70 deaths right now.
      That was 3500 infections 4 weeks ago.
      That’s 28,000 infections right now.
      That will be 112,000 infections by the end of March with ~300 deaths.
      Multiply by 16 to get you to the end of April if too many boneheads don’t take things seriously.
      The Chinese basically put almost the whole country under house arrest on the 1st of February. They may–MAY–have no active cases left on the 1st of April. But I doubt that such measures are coming to the Western world.
      Unless social distancing measures SUBSTANTIALLY reduce the average infection multiplier (how many new cases arise from old ones) from ~2, the math looks pretty much the same, just a question of where you decide to start from (% deaths from infections, time from infection to death, time for cases to double all hold fairly static since the virus isn’t really changing.)

      Failure looks pretty grim, and all the elements for failure–a fair percentage of reality-challenged population, barriers to care, disorganized leadership, pinch-points in care, multiple-single-points-of-failure, large and mobile vulnerable populations–are in place.

      Watch the Dow Jones–that’s a whole bunch of smart people with waaaaaaay more money than you have betting how bad this will get. How smart do you feel now?

  • Your math is horribly flawed. Infection rate in Italy is only 3 one thousandths of a percent,China lower, so if US is worst case, only 11000 cases, even half needing hospitalization is less than 6000.

    • You realize the article is estimating growth rates into the future, yes? Looking at the beginning of a pandemic and saying “there are not many cases so there’s nothing to worry about” isn’t the right approach. This kind of thing can get much worse very quickly if the correct steps are not taken to slow it down.

      This is the beginning of a long process.

    • I am having a hard time wrapping my head around Dr. Specht’s numbers as well. Perhaps she assumes that reported cases equal hospitalizations. My hunch is that Brad is more right than wrong. I assume he is comparing 2020 populations with data available on the Johns Hopkins COVID-19 site. The infection rate in China (mostly over the epidemic for now) was 0.006%. The infection rate in Italy currently stands at 0.04%. Using those as limits, the US reported total infections come out as between 132,400 and 19,860. Ten percent of those numbers are 13,240 and 1,986 so that is the hospitalization total. The fatality rate based on these two countries alone ranges 4-7% if my math is correct.

    • Dan – we are at the very beginning of this, make no mistake about it.

      China has managed to contain the current situation by completely shutting down much of its society. Once it begins to lift the quarantine, there is high likelihood of more spreading.

      Also, we should take into account that China is a totalitarian regime with high levels of centralized power. This actually gives them a strategic advantage with this situation, in many ways. They have been able to enforce the lockdown very effectively by using that power.

      If western governments are willing to introduce lockdowns for many months, we should see a successful slowdown similar to that in China.

      Again, calculating the current % of a population that is infected when the current numbers are following an exponential curve, is pretty much a null point. We are trying to understand where this will be in 2 months’ time if serious steps are not taken to tackle the problem.

    • You think the US can lock it self down like China did? that aint happening, you are moving towards a massive infection rate as the good doctor pointed out based on the figures.

    • Just because you have smaller numbers now more or less only means you are further behind in time on the same curve than other countries with higher numbers. With variations based on the overall age of your population, access to healthcare, containment measures already in place etc.

    • Italy is standing now at around 25,000 cases in a population of 60 million.

      You say USA is going to top out at 11,000 cases in a population of 300 million?

      Show your work, please. Let me try:

      US Cases / 300 million = 25,000 / 60 million

      US Cases = 125,000

      And Italy is still in exponential growth phase.

  • A very interesting and informative article.

    It should be mandatory reading for the bureaucrats and politicians making decisions on health care and policies for dealing with COVID 19.

  • The testing that is being done is of very limited value! If even a small number of random test were done we could ascertain the prevalence of asymptomatic carriers. We could also get a handle on how many people are infected and are within the incubation period. With testing of antibodies we could also determine the prevalence of individuates that have already had it and recovered with out medical intervention. This is all critical data if we want to know what to expect and plan effectively.

  • Has there been any attempt to include healthcare workers who have gotten covid-19 and recovered? Could they then return to work in an emergency situation without a mask? And is there any thought to having a wrist band or necklace given to a recovered civilian or healthcare worker (or later, waiter/waitress, cook, taxi driver, cashier, etc.) to indicate they are not at risk of carrying the virus?

  • If we target our sequestration efforts primarily at keeping our “over 60” cohort away from infected Individuals, we should be able to keep hospitalizations to a small fraction of the numbers seen in China or Europe (esp. Italy and Spain).

    It’s obvious that it would be our Boomers who would overwhelm our hospitals if most of them were exposed to the virus. Hospitalizations have been at far lower rates for those under 60.

    The Boomers will then need to remain sequestered until a vaccine is available…or at least until a good “herd immunity” level is established.

    I’m not hearing any strong emphasis from the CDC on keeping our elderly away from infection. Is this considered impossible?

    Learning from China’s apparent lack of community spread outside Wuhan, we should require anyone who has a fever to stay out of houses where our elderly live. That is one thing China did…lots of thermometer readings to and from work. If there was no good indication of “infectiousness”, then there would now be widespread outbreaks all over China. Instead they continue to report declining numbers of infections.

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