Bending the curve: are we flattening it?

There are two terms that are used complementary to one another to determine if a country has the pandemic under control.

Bending the curve refers to the graphical representation that the number of daily cases is plateauing and later on sees a continuous decline in the trajectory of the curve.

Figure 1. Are we bending the curve?
https://www.biospectrumasia.com/analysis/83/15734/covid-19-are-countries-bending-the-curve.html

Figure 1 above illustrates the current condition of various countries based on days since the first cases reached 30/day (X axis) and the number of cases (in logarithmic scale, Y-axis). One can see that there are countries that are still on an upward trajectory while others have begun to bend (slightly or significantly) their curves.

Has the Philippines bent its curve?

Figure 2. Daily confirmed deaths due to COVID-19 (United States, Italy, Indonesia, the Philippines, South Korea, and Brazil)
Figure 3. Daily vs total confirmed deaths due to COVID-19 (in red is the United States). Other countries illustrated include Brazil, Italy, South Korea. Indonesia and the Philippines.
https://ourworldindata.org/covid-deaths

Figures 2 & 3 above show how we are faring. And while the United States may have the most cases in the world, they have also begun to bend the death curve with less daily deaths vs total confirmed cases as well. Brazil on the other hand is the new epicenter in the world to watch out for as its death rates begin to climb staggeringly. Indonesia still has an upward trajectory for deaths (in proportion to their upward trajectory in cases, see Figure 6 below).

The other term used by epidemiologists is more commonly known as “flattening” the curve. Let me delve on this a bit as this has caused some confusion among the public.

Figure 4. Illustration of the concept of flattening the curve. https://www.livescience.com/coronavirus-flatten-the-curve.html

Flattening a curve does not imply that the curve should flatten to ZERO. It is a misconception among lay that a curve in order to be called “flattened” is pressed to the ground.

In a pandemic, the curve varies in shapes from country to country, with some countries taking a steeper climb than others. As a general rule, when a country has a steeper rise in cases (more people get infected), it will also have a steep fall (the patients either get better or die because the virus has infected a large segment of the population already).

A steep rise in cases carries a large burden on the health system. Too many sick people overwhelm the healthcare system and overloading beyond the capacity to treat people results in greater death rates. More people die not only because there are no more hospital beds, but the overall health system – from healthcare workers to basic supplies – are exhausted rapidly.

Interventions like the ECQ and social distancing, hygiene, wearing masks and other ways at minimizing the transmissibility of an infection from one person to another (i.e.. school closure, limiting travel and work, closing borders and minimizing movements) are ways to flatten the curve. A flatter curve does not mean that we pummel the curve to the ground (although wouldn’t that be great?). When we flatten the curve, we slow down the infection rate. It assumes that the same number of people eventually get infected, but over a longer period of time. Slowing down the infection de-stresses the health care system.

That’s the story of the COVID-19.

There is currently no vaccine or drug to treat this disease and we’re all scrambling at the availability (or unavailability) of testing. The collective action of everyone in the community is needed in order to address the challenge of seeing a decline in the cases of COVID19.

Have we flattened our curve?

Figure 4 above illustrates the health care capacity of a country in the broken lines. Without precautions during a pandemic, the number of people infected would be disproportional to the health care capacity resulting in a direct collapse of the health system and indirectly leading to more deaths. The “flatter curve” (in orange hue) has the same area under the curve (number of patients) but spread out over a period of time when compared to the more steep curve (in dark pink when no precautions are observed).

Figure 5. Image from the CDC and criteria for claiming “flattening of the curve”

There are two major criteria (shown in figure 5) to say that the curve has flattened. (1) Slow acceleration of number of cases, and (2) reduction in the peak number of cases and related demands on hospitals and infrastructure. I would boldly venture on saying that the overall reduction in death rate is an ideal parameter to indicate that we’ve reduced the demand on hospitals and infrastructure.

https://www.doh.gov.ph/covid19tracker

As of May 20, 2020, the DoH reports that facility capacity of various hospitals in the Philippines is not overwhelmed. Only 34.5% of total ICU beds and 17.8% of mechanical ventilators are being used.

The death rates have also dramatically dropped weekly. From April 26 – May 2, the average deaths was 16/day. May 3 – May 9 showed an average of 15/day. May 10 – May 16 an average of 16/day. May 17 – May 23 show a dramatic drop to 6/day.

Number of new confirmed cases are also on the decline. The last 4 weeks (since April 26) saw a 7 day average of 240 cases/day. To say that we’re slowing the acceleration of cases is to see a conservative decline by at least 10% from the average of the previous week. We ended last week with an average of 242 cases/day. I wanted to test the threshold of 225 cases/day for the week. THE 7 DAY AVERAGE FOR THE WEEK OF MAY 17-23 is 210!

With this new 7 day average for last week, we now test the threshold of 190 cases/day for the coming week. If this is sustained in spite of latent data, then we can confidently say that we have not only begun to, but we have flattened the curve. (This has to be something consistently seen over a 4 week period).

Figure 6. Daily vs Total confirmed COVID-19 cases (US, Italy, Philippines, Indonesia, South Korea and Brazil)

Figure 6 above shows the Philippines and the United States plateauing on cases, with Brazil now in an upward trajectory. A plateauing of cases means a slowing down in the trajectory (shifting the curve to the right). If we sustain at declining by 10% the weekly threshold, we will have similar bending curves as South Korea and Italy. While Indonesia may have lower death rates compared to the Philippines, its cases remain on an upward trajectory and have not plateaued yet.

Statistics for the day

The world is now at 5,328,548 confirmed cases with 340,425 deaths (6.39% case fatality rate) and 2,175,290 recoveries (40.8% case recovery rates). The ratio of recoveries to deaths is higher at 6.4:1.

Back home in the Philippines, the Department of Health has publicly announced 180 new cases, 85 new recoveries and 6 new deaths.

https://covid19stats.ph

Our case fatality rate has improved and is now down to 6.26% with recovery rates up at 23.06%. Globally we rank now lower in recovery rates at 140 (out of 165 countries), and are doing much better at number 30 (from number 29) in death rates.

The Department of Health website has not updated the Data Drop files as of this writing but reported that of the 180 new cases today, 114 (63%) are from the NCR while the remaining 66 (36%) are from others. The NCR remains to be a hotspot contributing to more than 60% of the daily cases reported in the Philippines.

Update (May 24, 2020)

Based on the DoH website this morning of the 114 cases in the NCR, Quezon City is back on top of the heap (25), followed by Manila (23) and Makati (16). The rest include: Caloocan City (15); Malabon (6); Marikina and Mandaluyong (5 each); San Juan (2); and Parañaque, Pasig, Taguig, Pasay City, Muntinlupa, Las Piñas and Pateros with 1 apiece. Only Navotas had no reported case yesterday. There were 9 cases for validation.

Of the remaining 66 cases, almost 60% was from Davao City alone with 38 new cases. The rest were from Rizal (4), Laguna (1), Cavite (5), Batangas (1), Quezon (1), Bulacan (3), Bataan (3), Nueva Ecija (1), Iloilo Province (1), Iloilo City (1), Baguio (1), Cagayan de Oro (1), Cotabato (1), Surigao del Norte (1) and the remaining were for validation.

Testing Capacity

https://www.doh.gov.ph/covid19tracker

As of May 22, 2020, a total of 287,294 tests have been done among 265,061 individuals with 20,264 testing positive (7.6% positivity rate). There were a total of 9,504 tests done yesterday alone (6% of who were positive). As of yesterday, there are 7,128 samples in the backlog.

Disclaimer: All information provided in the daily reports and updates are based on the Data Drop of the Department of Health website. The accuracy of information is dependent on the information released from the DoH. All other graphs, citations and projections are referenced appropriately. Any change in future data particularly on latency reporting may affect the overall trend cited in this post.

2 thoughts on “Bending the curve: are we flattening it?

  1. jaesonv May 27, 2020 / 11:08 pm

    Hello Benjamin. I enjoyed reading your perspective on the matter of “flattening the curve”. Pretty solid and grounded approach that won’t have the reader bat an eye.

    DOH mentioned a few weeks ago that they’ll work with other countries and, maybe, other health organizations to look into measures regarding SARS-COV-2. This leads me to think about how the Government as a whole is approaching management on COVID-19. If I remember it right, MERS is a disease that does not have a cure currently.

    I saw Dr. Michael Levitt’s take on data analysis about COVID-19 thru Ivor Cummins who has been advocating a data-centric approach and science-based response to the 2019 Corona virus. I think you’ve already read on Dr. Levitt’s work but let me just state it here a bit – after using Gompertz function to look at the growth rates for COVID-19 (wasn’t just Levitt but others as well) he saw a declining growth rate for COVID-19 worldwide and not something exponential. Norway, who is now on the road to recovery from COVID-19 has their Director General of the Norwegian Institute of Public Health stating that they could have approached the lockdowns less stringent and allow some legroom, especially for their economy, schooling, and life in general. Israel has taken the same path, if I’m correct.

    How I understand it is that Dr. Levitt has taken a mathematical, follow-the-data approach. The realm of epidemiology is different from what I’ve seen several agencies and universities have looked into the forecasts for COVID-19. Dr. Patrick Lam created a web app where he implemented Dr. Levitt’s findings at covibes.org.

    Assuming SARS-COV-2 does not have any known cure or vaccine developed in the next 60 months and the upper house is contemplating an extension of RA 11469, what could be a viable set of considerations that we can look into to help us decide how we’d move forward on the concern of a continued quarantine implementation or the relaxing of such measure that is, just to limit it, applicable for Metro Manila if not the whole archipelago?

    Like

    • kidatheart June 3, 2020 / 6:16 am

      Good question. No definite answer. At the data we currently have, this looks like a viral infection similar to a very bad flu. The outbreaks we see are mostly in dense communities. The deaths are mostly also in the most vulnerable (elderly and comorbids). Unlike influenza, there are treatment options and vaccines available. This has nothing to offer except personal immune response. This means that we just need to be more careful on how we engage in crowds and be more conscious of hygiene. After all, by doing that the virus will dissipate if not “weaken”. No virus has ever lived without a host. The less the hosts get it, the less likely it is to survive and continue thriving.

      Like

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