Question: When they are counting deaths from COVID, do you know if they are also counting secondary infections and/or underlying contributing factors on death certificates? It would be interesting to know how many of the deaths would also be counted as antibiotic-resistant infections. And when death statistics are compiled, does one death with multiple causes listed get listed as 4 deaths when listing the causes? For instance, my father-in-law recently died and they listed four causes — head and neck cancer (the underlying issue of course), lung infection (the pneumonia), kidney failure (as a result of his body fighting the infection) and I think ultimately something having to do with his lungs being filled with fluid. So ultimately it was the fluid that killed him, but the others obviously contributed. So when they collect the statistics, does his death count as “pneumonia”? or “head-and-neck cancer”?

Answer: This is a great question, thanks for asking. And I’m sorry for your recent loss of your father-in-law.

A longer answer follows, but here are the short answers to your questions, 1) multiple causes are counted; 2) antibiotic-resistant infections are counted, but for COVID-19, I don’t believe the data are available yet; 3) underlying cause is what’s counted when you’re looking at most cause of death tables (e.g. head and neck cancer). Now for the longer answer…

Recording Deaths

A “medical certifier” (e.g. coroner or health professional) completes Section 2 of the death certificate (Figure 1). The medical certifier lists the “underlying cause of death,” which is defined by the WHO as “the disease or injury which initiated the train of events leading directly to death, or the circumstances of the accident or violence which produced the fatal injury,” as well as the other conditions that contribute to the death (up to 20 conditions can be listed). The conditions are listed in causal order with the underlying cause being the lowest on the list (like the order you shared in your question). Per CDC, in the United States “there is an average of three causes listed per certificate. Approximately 20 percent have only one cause of death and 45 percent have three or more causes.”

Coding Deaths

After the medical certifier completes the bottom portion of the death certificate, the funeral director typically completes the top portion. Thereafter, the certificate is sent to the State’s vital statistics office (or the like) and each State then sends these certificates on to CDC’s National Center of Health Statistics (NCHS). At NCHS, the data are entered into a specialized computer system and either the computer or a trained coder translates these conditions into International Classification of Diseases, Tenth Revision (ICD-10) codes. These codes are used worldwide to enable comparable cause-of-death mortality data collection and analysis. And yes, these codes can be very specific, including specific codes for antibiotic resistant infections.

Tabulating Deaths

When it comes to aggregate statistics, cause of death data is reported in two ways: 1) underlying cause and 2) multiple cause. You use both sets of statistics for different, complementary analyses. The “leading cause of death” tables we frequently see or “top 10 causes of death” are based on underlying cause data. We also need to focus on multiple cause analysis to understand disease interaction, and consider other interventions to reduce mortality. This paper from Epidemiology gives a nice description of both types of statistics.

Calculating COVID-19 Deaths

This process applies to COVID-19 too. CDC describes COVID-19 death recording here and death coding and tabulation here. While in most cases, COVID-19 will be the underlying condition, CDC’s counts of COVID-19 deaths may include those for which COVID was the contributing cause depending on the analysis. Additionally, the ICD-10 code for COVID-19 (U07.1) is applied not only to “confirmed” deaths, but also to those that are “presumed” and “probable” (e.g. without laboratory confirmation). A couple of relevant notes:

1) CDC also collects death counts from states on a daily basis. These counts, listed here, are different from the counts listed with NCHS, which are always several weeks behind because they are based on death certificates received and entered into NCHS’s system; and

2) Our World in Data offers a really nice description of COVID-19 mortality around the world, including great graphs (for example, see Figure 2). I highly recommend!

Figure 1. U.S. Standard Death Certificate

Figure 2. Daily Confirmed COVID-19 Deaths (from ourworldindata.org)