Category: Research

Categories
Perspectives Research

Underlying Conditions

Our city today surpassed 170 identified COVID-19 cases. Regretfully, 7 patients have died. We continue to see here, and around the country, that certain individuals have a higher risk of severe illness and death from COVID-19. Most of those who have been lost were over the age of 65 and/or had underlying conditions.

In this post, my goal is to help decipher what is meant by “underlying conditions” and why people that have them also have the highest risk for the worst COVID-19 outcomes. My second goal is to call attention to the other underlying conditions that are being overlooked.

Underlying conditions, simply put, refer to other diseases and disorders that are sort of operating in the background, before a person ever becomes infected with coronavirus. [FYI, you may also hear underlying health conditions referred to as co-morbid or co-occurring conditions]. People with underlying health conditions are of generally worse health and are, thus, at a distinct disadvantage when it comes to overcoming COVID-19. Starting behind the eight-ball, so to speak.

In addition to old age (which typically brings underlying health conditions along with it), research out of China and Italy has showed us that some underlying health conditions are independent risk factors (irrespective of age) for severe COVID-19-related outcomes including hospitalization, need for intensive care, and death. Just this week, the Centers for Disease Control released the first US data on the link between underlying conditions and severe COVID-19-associated outcomes.

The CDC looked at a long list of underlying health conditions including lung disease (asthma, COPD, and emphysema), diabetes, cardiovascular disease, kidney disease, liver disease, immuno-compromised conditions, and neurological and developmental disorders, among others. They even took it a step further to include some of the more general risk factors for severe respiratory infections – factors like smoking and even pregnancy (think gestational diabetes). Here are the main findings:

Key Study Findings

71% of hospitalizations and 78% of COVID-19 patients admitted to the ICU had one or more underlying health condition.

By comparison, just 27% of COVID-19 cases who were not hospitalized had an underlying health condition.

In general, cases with underlying health conditions were significantly more likely to be hospitalized and more likely to be admitted to an ICU than those without.

Among the 184 deaths included in this analysis, 94% of deaths were patients with underlying health conditions.

The most commonly reported underlying health conditions were diabetes (10.9%), chronic lung disease (9.2%), and cardiovascular disease (9.0%).

It is important to note that this information may not be telling the whole story. First, of the 122,000+ plus US cases identified at the time of this report, information on underlying health conditions was only available for 7,000 (or 5.8%) of them. These small numbers, and the fact that we are still early in the spread of COVID-19 in the US, limit our ability to generalize these findings to the US as a whole. Only the presence or absence of these conditions was known and not their severity or whether or not they were being treated, both of which may have an impact on COVID-19 outcomes.

Still, the research all seems to agree that people with underlying health conditions are at significantly increased risk of more severe COVID-19 outcomes. Of major concern to us is that so many Americans have health issues that are tied to these underlying conditions. Things like obesity, which is linked to diabetes and cardiovascular disease; and smoking, which is tied to lung disease. Even asthma, which impacts about 8% of Americans, could complicate respiratory infections. These too should also be considered risk factors for severe COVID-19 illness. And this is where we get to the other underlying conditions.

The other underlying conditions

All of the other health problems that we had before COVID-19 didn’t just disappear once COVID-19 showed up. People are still having heart attacks. Still getting cancer. Still struggling with mental health and substance abuse problems. Perhaps even more so than ever. In fact, all of these conditions are likely to be exacerbated by the current COVID-19 pandemic.

Limited access to healthy food options; limited physical activity; increased exposure to poor indoor air quality; psychological stress, anxiety, and depression from the general state of affairs, social isolation, or the loss of a loved one. All can lead to poorer health and all are happening right now. At the same time, we may think twice before leaving the house to see our doctors. Or worse, because of the strains on our healthcare system, there may not be a bed for a heart attack patient or a doctor to mend a broken bone at the hospital.

Health inequities are also being exacerbated with some of our most vulnerable and disadvantaged citizens being impacted the most by this pandemic – by the virus and its economic consequences. These are the underlying conditions of our health and of our society that have been operating in the background since long before we were ever exposed to COVID-19. Now, they may be spreading, even faster than the virus.

Study: Preliminary Estimates of the Prevalence of Selected Underlying Health Conditions Among Patients with Coronavirus Disease 2019 — United States, February 12–March 28, 2020. MMWR Morb Mortal Wkly Rep. ePub: 31 March 2020. DOI: http://dx.doi.org/10.15585/mmwr.mm6913e2external icon

UPDATE (4/2/20): NYC released a data summary of underlying conditions among COVID-19 deaths to date. Over 98% (994/1012) of all NYC deaths (with confirmed health history) had one or more underlying condition. About 75% (1012/1374) of NYC COVID-19 deaths have confirmed health history (25% still pending).

LAtest Posts

Categories
Planning Research

Summer Reprieve?

A fascinating new study suggests that the transmission of COVID-19 may fluctuate seasonally, and that the spread may slow down as temperatures rise. On the flip side, we may see a resurgence of the virus heading into fall and winter.

Key Study Findings
  • Warmer temperatures by 1°C (1.8°F) reduced the transmission rate of COVID-19 by 13%.
  • Changes in temperature from March to July 2020 may lead to a 43% decrease in COVID-19 transmission in Northern Hemisphere countries like the US.
  • Southern Hemisphere countries may see a 71% increase in transmission during the same period.
  • By winter 2021, the US may see a resurgence of COVID-19 with a 59% increase in transmission from the current (March 2020) rate.
  • Due to the potential seasonality of COVID-19, northern countries like the US may have a window of opportunity over the summer months to recover and to prepare for a possible resurgence in winter.

The study, posted yesterday as a preprint (ahead of being accepted for publication), found that higher temperatures decreased the number of new COVID-19 cases in a community. The authors looked at data from 134 countries based on 166,686 COVID-19 cases diagnosed between January 22 and March 15, 2020. They found an average decrease in transmission rate (the number of new cases) across all countries was 13% for every 1°C (1.8°F) increase in temperature. This drop in transmission can have a major impact on total case numbers, particularity in areas currently suffering from a high rate of spread, like New York and other major US cities.

By modeling these findings out further, using projected temperature changes from April 2020 through January 2021, the authors predicted a 43% decrease in COVID-19 transmission across the Northern Hemisphere by July 2020 compared to today. Because the Southern Hemisphere is heading into its winter months, the authors project a 71% increase in new cases over the next 3-4 months – an alarming finding that should be noted by health officials in Southern Hemisphere countries.

As a warning to the US and other countries of the Northern Hemisphere, the study also reported a possible resurgence of COVID-19 by winter, with a 59% higher transmission rate in January 2021 compared to the rate today. This means that while we may experience a period of recovery over the summer months, we should also take that time to prepare for the next potential wave of cases. We may continue to see this seasonal ebb and flow of cases until we either reach a critical threshold for herd (community) immunity, or we have a COVID-19 vaccine, which most believe is 12-18 months away at best.

So why does temperature have anything to do with how a virus spreads? There are a number of possible mechanisms including temperature playing a role in attenuating (weakening) the virus itself. Other possibilities are that warmer temperatures encourage outdoor activities, which naturally results in more social distancing versus when people are confined to indoor spaces and are in close proximity to one another. Also people are generally healthier in the warmer months, when other seasonal illnesses are less of a threat.

This research provides clues as to whether we can expect the transmission of COVID-19 to shift as temperatures shift around the globe. However, these projections are based on early case numbers, most of which were concentrated in Europe and Asia. The authors did account for differences across countries (and regions within countries) in population density and health system capacity including the amount of COVID-19 testing, and still saw the relationship with temperature.

We can expect to learn a great deal more about the seasonality of COVID-19 as more cases are identified and as temperatures change. The authors suspect we may eventually see an even stronger impact of temperature on transmission. We may not know for sure until it happens. Until then, countries should continue to respond to the COVID-19 threat at hand. We can hope for a summer reprieve, but must also consider a possible resurgence come cooler months. Countries heading into the winter now should be aware of the potential for an increase in transmission of COVID-19.

Study: Tamma Carletonk and Kyle C. Meng. Causal empirical estimates suggest COVID-19 transmission rates are highly seasonal. medRxiv preprint doi: https://doi.org/10.1101/2020.03.26.20044420.

Accessed March 30, 2020.

Latest Posts
Categories
Research

Hindsight is 1918

We can learn from the past. And 102 years is a long time to prepare for the next pandemic. So what did we learn in hindsight from the 1918 Pandemic Flu, and is it too late to keep history from repeating itself in 2020?

I wonder if she is posting to her H1N1-18 Journal

A New York City typist wears a flu mask while at her desk, October 16, 1918 National Archives and Records Administration
Influenza Encyclopedia, University of Michigan Library

I’ll admit it. When our schools closed before there were any known cases in the community and before any neighboring cities closed theirs, I questioned whether there was any science that justified my kids being home (and invading my office). Well, I dug up some evidence and it turns out that preemptive school closings during the 1918 flu pandemic was a key social distancing ingredient that saved tens of thousands of lives, if not more.

In St. Louis, schools closed within about 2 weeks of the first flu case to be identified, and about two weeks before the virus began to peak in the community. In Pittsburgh, schools closed about 6 weeks after its first case and almost 2 weeks after the flu began its peak in the city. What we saw was a sizable difference in the number of deaths in St. Louis compared to Pittsburgh, where the rate was 2.25 times higher.

Weekly Excess Death Rates From September 8, 1918, Through February 22, 1919; adapted from Nonpharmaceutical Interventions Implemented by US Cities During the 1918-1919 Influenza Pandemic

Seems like Pennsylvania as a state was slow to react to the pandemic. Philadelphia, much like Pittsburgh, waited weeks after the first known cases before it implemented any social distancing measures. St. Louis, as we know, took much quicker action. The result, a dramatic “flattening of the curve” in St. Louis and, again, the cumulative death rate was cut in half.

1918 influenza related death rate in Philadelphia and St. Louis; from Public health interventions and epidemic intensity during the 1918 influenza pandemic

Looks familiar, right? So we did learn something from the 1918 flu pandemic. The question now is whether we’ve acted on it soon enough.

As Long as it Takes

Now something you wont want to hear. We actually want the spread of COVID-19 to last as long as possible. It sounds counter-intuitive, but it is true. We need to stretch it out as long as possible if we want to save as many lives as possible.

Take a look at St. Louis versus Philadelphia again. Before, we were so interested in the death rate (the y-axis) that we forgot to look at the timeline (the x-axis). The Philadelphia outbreak was all said and done by early November, whereas the St. Louis outbreak lasted 2 more months, until the end of the year. However, for every 1 person that died in St. Louis over the course of the pandemic, more than twice that number died in Philadelphia. The city had more than 12,000 deaths in total.

The US as a whole lost 675,000 lives to the 1918 pandemic.

Lets hope we learned our lesson and that the measures we are taking to slow the spread of COVID-19 started soon enough and last long enough. Then again, we always could have started sooner. Hindsight is 20/20…

Want to learn more about the 1918 flu pandemic in America? Visit the Influenza Encyclopedia by the University of Michigan.

influenza encyclopedia
Latest Posts
Categories
Research

Early Data

The Centers for Disease Control (CDC) just released some of the early data on severe outcomes, including hospitalizations and fatalities, for the first 4,226 COVID-19 patients in the US. Health officials have been relying primarily on data from other countries like China and Italy, whose populations and healthcare systems are not necessarily comparable to our own. Though this continues to be an evolving situation, this early research is telling. It supports something we know, and raises a red flag on something that needs more attention.

Case fatality rates

Forty-four COVID-19 cases with known status had died as of March 16, 2020. That represents approximately 1% (1 in 100) of identified cases. (I will address whether this is a true representation of case fatality rate later on). Cases 85 years-old and above had the highest fatality rates, ranging from 10% of all cases in that age group, up to 27% of those hospitalized (Table). Among cases 65-85, 3-11% had died. The case fatality rate among those ages 20-54 was less than 1%. This is in line with what we have learned and heard previously about COVID-19 – that older individuals are heightened risk of dying. What we learned next was somewhat more surprising.

Case Hospitalization rates

Among the 12% of cases (508) with a known hospitalization, we again saw that the highest number of patients, 35%, were cases over the age of 65. However, we also saw that younger patients, between the ages of 20 and 54, made up 38% of all hospitalizations. This suggests that although the risk of death is lower for younger individuals, they are still at risk of severe disease that requires hospitalization. This is important because it addresses a dangerous misconception that young, healthy people are not at risk of serious illness from COVID-19, which has been a detriment to social distancing measures enacted to slow the spread of the virus.

what does this all mean?

This are very early data based on what will amount to be a very small number of the cases we see in this country. The analysis was limited to the 2,449 cases whose age was known. Further, these data are still incomplete. Most cases are still unresolved. Some may still be hospitalized or yet-to-be hospitalized. Some may die. Most will recover. The report also did not include information about underlying health conditions, which we know also increase the risk of death.

When it comes to case fatality rate, we are not yet seeing the full picture. These initial cases came before widespread testing was made available in the US. In other words, these cases likely came to our attention due to illness or because they were exposure to an already confirmed case. Some evidence suggests that for for every confirmed case, there are 7 more that have yet-to-be identified.

The number of identified cases will continue to rise in the US, and with that increase in cases, the true case fatality rate will surface. If China is any indication, we can anticipate it to be closer to 0.1% (1 in 1000) or less.

Table: COVID-19 severe outcomes by age – United States, february 12-march 16, 2020
Age group (cases)Hospitalization ICU admission Fatality
0–19 (123) 1.6–2.5 0 0
20–44 (705) 14.3–20.8 2.0–4.2 0.1–0.2
45–54 (429) 21.2–28.3 5.4–10.4 0.5–0.8
55–64 (429) 20.5–30.1 4.7–11.2 1.4–2.6
65–74 (409) 28.6–43.5 8.1–18.8 2.7–4.9
75–84 (210) 30.5–58.7 10.5–31.0 4.3–10.5
≥85 (144) 31.3–70.3 6.3–29.0 10.4–27.3
Total (2,449) 20.7–31.4 4.9–11.5 1.8–3.4

Lower bound of range = percentage among total in age group; Upper bound of range = percentage among total in age group with known hospitalization status, ICU admission status, or death; Table adapted from CDC.

LATEST POSTS