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.

  • Have you seen the posts by scientist on Twitter saying the doubling rate in Italy/ UK / Germany / France is actually much faster, like 3 or 4 days? Chinese people may be a bit more into home sanitation than westerners… So definitely update this when you find Italy / EU data.

  • Excellent piece. With all of the students about to begin remote learning, could we issue a challenge for design and manufacturing of masks? And what companies want to retool and enter the market? Easier to sell masks than cars, airline seats, etc.

  • Here are the author’s credentials:

    As Associate Director of Science & Technology with GFI, Liz analyzes areas of current and future technological need within plant-based and cell-based meat innovation, catalyzes research to address these needs, and supports start-ups and investors who are moving the field forward.

    Liz has a bachelor’s degree in chemical and biomolecular engineering from Johns Hopkins University, a doctorate in biological sciences from the University of California San Diego, and postdoctoral research experience from the University of Colorado Boulder. Liz is a Community Fellow with CU Boulder’s Sustainability Innovation Lab and a Guest Lecturer for Singularity University. She has a decade of academic research experience in synthetic biology, recombinant protein expression, and development of genetic tools.

    I have a PhD in Physics, and a graduate epidemiology course from Harvard Medical School.

    What are your credentials? Fox trolls speak up!

  • A very important and sober perspective- even IF the COVID-19 strain may spread less with warmer weather; even IF exponential growth rates could slow down ‘sooner’; even IF there are major quarantines; even if the virus were to become less harmful as it spreads (which can happen in the evolution of certain viruses)- the safest assumption is that without a degree of quarantine equalling China’s (rather unlikely in a much less authoritarian society such as in the western world) that there is both a guessing game regarding whether critical medical overwhelm is reached, and its spillover effects into the nations involved (economic, etc), given its current exponential trajectory through most of the world, there’s a crucial race (or unfortunately, stride) against time now underway, as mitigating factors may merely delay dates of reckoning. The prudent public health perspective is to lean toward expecting worst-case or serious scenarios rather than rosy ones.
    Many laypeople don’t understand this because the question for them comes down to- “is it very deadly or not?,” not “could a much greater incidence of hospitalization case flood the ‘chokepoints’ in our system (which is the point of the article); or “there’s only ‘x’ no. of cases,” the latter perspective due to individuals’ tendency to not pragmatically grasp exponential growth effects (the inability to do so actually being a documented finding from research on cognition).
    For all those in the US who believe that grave concern here is merely a political slant or hysteria, it helps to look at the massive and unprecedented efforts of China, which obviously does not have our political dynamic, to take this issue with the utmost degree of seriousness. The apparent coping curve in that nation has only occurred due to a program of response based upon grave concerns about the public health risk from this virus. The response was not guided by a court of public opinion- presumably there was a reasonable degree of scientific analysis involved in the mix. Naysayers on this issue would do well to consider this.
    Great article!

  • 1. We are told that masks are only to stop hand contamination, that this is not airborn and yet, health workers are falling victim to it?
    If the former were that case, masks would be reusable surely?
    2. Are your figures worked on chronic
    cases or over total infections?
    If the figures out of China to be believed, then it appears they are winning the 3d world war without leaving home…They have certainly brought down the world economy…
    If our politicians were as diligent at border protection as they are at scrambling for position, they might have seen this coming.

  • your simple math is really quite to simple for you!!! using your example of 1 million by the end of april leaves 5 million @ the end of may. the end of june there would be a staggering 30 million and July would have over half our population w/wu-flu. ( oops thats not politically correct but then political correctness is PROOF stupidity is contagous!!!) 30 days in may means it would double the rate every 6 days not every 30!!! If you’re going to be disimenating fear you should probably have somebody else do your numbers!!

  • The amount of right wing Fox News level sophistry on this thread is mind blowing. Just like the flu. No exponential growth. Fuzzy math. Anyone who is a working epidemiologist identify yourself please. Anyone who has taken a graduate level course in epidemiology identify yourself. Paying attention untrained amateurs (some are most likely trolls) is a mug’s game.

    We are not seeing cases because we are NOT TESTING widely. Korea and China brought their pandemics under control because 1) they were PREPARED (compared to the USA), 2) their societies have a level of social control and surveillance that does not exist in the USA, 3) they have universal health care systems, unlike the USA.

    The American Hospital Association was briefed on 26 February by a consulting epidemiologist, James Lawler, MD, MPH, a professor at the University of Nebraska Medical Center. Dr Lawler served as a member of the Homeland Security Council for President George W. Bush and as a member of the National Security Council for President Barack Obama. Here is a brief summary:
    4.8 million hospitalizations associated with the novel coronavirus
    96 million cases overall in the US
    1 million ICU cases
    1 million cases requiring a ventilator
    480,000 deaths
    Peak load is 2 months from now.

    People aged 80 and over have a 14 per cent chance of dying if they have the infection, Dr Lawler estimates.

    Those aged 70 to 79 and 60 to 69 have an estimated mortality rate of 8 per cent and 3.6 percent if they contract the virus.

    Medical conditions can also influence someone’s risk. Dr Lawler estimates those with heart conditions would have a one and 10 chance of dying from the disease.

    Overall, the slide points out that hospitals should prepare for an impact to the system that’s 10 times a severe flu season.

    Here is another good primer on the issues https://www.fast.ai/2020/03/09/coronavirus/

  • Why should we believe you, CP? Who are you? What are your credentials? Source of statistics? Political affiliations? At least Liz Specht usess her full name and can be checked for credentials.
    You could simply be a Russian bot.

  • This is fear mongering at its finest. Referencing a study from Jan 31 that says as of Jan 25 China had 76k cases. As of today, Mar 10, there are 81k total cases with virtually no new cases being reported.

    Along with South Korea being at the tail end of their reports, and Japan completely halting the spread of it.

    • You do realize China is a totalitarian regime, right? That has over 750 million people in lockdown, right? You realize that the numbers coming from China are massively suspect, right? You realize that the numbers coming from everywhere other than China show exponential growth, right?

      Even IF the numbers coming from China are accurate, which is a near impossibility, the only way they’ve managed to achieve this level of containment is through totalitarian lockdown of much of the country. Western governments may not have those tactics available to them.

      It blows my mind that so many people find this so hard to grasp, honestly.

    • What are you talking about.. As of march 8, there were 500 cases in the united states.

      As of yesterday, march 9, there was 700

      As of TODAY, there is a whopping 900+ cases (and the day isnt over yet).

      This is WITH the lack of adequate testing in the US.

      Youre comparing South Korea, a nation who took this epidemic as seriously as it could early on, with the US, who is lagging behind and has barely started to enact measures. China also took this seriously and halted it from becoming more serious.

      The US’ action is laughable, compared to what’s getting done in other countries. Thats the whole point of the article…

      Or did you not read it?

    • So you clearly didn’t read the article. The reason why China and SK aren’t seeing the same degree of exponential growth is because they took early and aggressive steps to mitigate the spread by shutting things down and doing aggressive social distancing. The US, like Italy, have waited too long focusing on a containment strategy and so now we have no choice – mitigating the spread is our only hope. That’s not fear mongering – it’s survival. Unfortunately uninformed, irresponsible clowns keep trying to ignore and blow this off and challenge the experts and the numbers. There are models behind this and the models are developed using real events. This is a crises and we’re only at the beginning. China however has achieved simple arithmetic growth, meaning they have new cases but they aren’t growing at an exponential rate. We aren’t even close to that yet – not until everyone takes this seriously and we start start making major changes to limit exposure.

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