COVID-19 Demographic Factors

There has been a lot of discussion about race and other demographic differences in communities showing up as higher death rates for example for Blacks and Hispanics.  But it is important to understand the concepts of infection rate, death rate, and mortality rate for a pandemic.  Death rates, the number of fatalities in each subpopulation divided by the number of people in each subpopulation, while stark and headline-grabbing, is not so important in terms of disease understanding and control.  It is a point in time measurement that increases monotonically as a disease progresses from zero to some large scary number.  Different communities may experience the disease at different starting points so it is often meaningless to compare this metric among different communities.  Infection rate, the number of confirmed cases divided by the number of people in each subpopulation is important and indicates how susceptible each group of people may be to a disease.  Fatality rate, the number of deaths in a subpopulation divided by the number of people in each subpopulation that catches the disease is important because it reveals how certain risk factors are causing them to die more often than others who catch the disease.

Let’s look at how these 3 metrics apply to the COVID-19 outbreak in California (CA) as of May 3^rd.  The table below shows that the number of confirmed cases for Latinos constitute 47.5% of all confirmed cases in CA.  This might suggest that Latinos are suffering more from the Pandemic.  On closer inspection, the percentage of Latinos who die from COVID-19 constitute 34.3% of all deaths in CA.  This suggests that COVID-19 might be less fatal for Latinos.  When we calculate the fatality rate for Latinos it is just 4.1% versus 7.6% for Whites and 5.7% for all Californians (note that this coincident fatality rate may be understated due to differences in timing between diagnosis and death).  But this also would be jumping to the wrong conclusion. 

Race/Ethnicity	​No. Cases	Percent Cases	​No. Deaths	Percent Deaths	% CA population	Fatality Rate
Latino	17,716	​47.5	720	​34.3	​38.9	4.1%
White	9,607	​26.2	730	​35.1	​36.6	7.6%
Asian	4,320	​11.8	355	​16.8	​15.4	8.2%
African American/Black	2,330	​6.3	216	​10.4	6.0	9.3%
Multi-Race	318	​0.9	8	​0.4	​2.2	2.5%
American Indian or Alaska Native	71	​0.2	7	​0.3	​0.5	9.9%
Native Hawaiian and other Pacific Islander	416	​1.1	20	1.0	​0.3	4.8%
Other	2,186	6.0	36	​1.7	​0	1.6%
Total with data	36,964		2,092			5.7%

The reason that the Latino fatality rate is so low compared to that for Whites is that the median age for Latinos is 27 versus 39 for Whites in CA.  The table below breaks out the CA data into 4 age groups.  You can see that there is a disproportionate number of young Latinos (0-17) that got infected but had zero fatalities that pulled down the fatality rate for the whole ethnic group.  The 0-17 age group had no fatalities – a phenomenon seen in many other countries.  Latino fatalities in other age groups are all consistent with the age dependence we found in every country we studied.  Similarly the apparent higher than average fatality rate for Whites, 7.6%, compared to the state average, 5.7%, can be explained by the higher than average age of Whites in CA.

Asians, especially the young, seem to catch it less often than the population in general (11.8% cases vs 15.4% by population). This may be due to their wider acceptance of mask-wearing in general for disease prevention.  But when they do catch it Asian mortality is higher especially for the 65+ group at 25.9%).  The higher prevalence of multigenerational Asian families may expose more highly vulnerable grandparents to COVID-19 than average.  More data is required to check out this theory. 

Blacks seem to catch the disease no more and no less than their share of the population (6.3% of all cases vs 6.0% of the population), unlike in many other cities in the US.  However, they do seem to die more often for every age group, although the statistical significance is somewhat marginal at this point due to small numbers.  Poorer health and higher comorbidities may play a part that could be examined further with additional data. 

	0-17	18-49			50-64			65+
	Cases	Cases	Deaths	Fatality	Cases	Deaths	Fatality	Cases	Deaths	Fatality
Latino	745	9,979	91	0.9%	4,511	153	3.4%	2,473	476	19.2%
White	118	3,670	11	0.3%	2,546	74	2.9%	3,267	645	19.7%
Asian	50	1,892	10	0.5%	1,205	44	3.7%	1,164	301	25.9%
African American	21	949	18	1.9%	679	36	5.3%	681	162	23.8%
Multi-Race	8	183	-	0.0%	76	1	1.3%	50	7	14.0%
Indian or Native	4	39	2	5.1%	15	1	6.7%	13	4	30.8%
Hawaiian and PI	1	206	1	0.5%	127	3	2.4%	82	16	19.5%
Other	41	1,120	-	0.0%	610	5	0.8%	413	31	7.5%
Total with data	988	18,038	133	0.7%	9,769	317	3.2%	8,143	1,642	20.2%

The lesson here is that early data in a pandemic, especially in terms of death rate differences may turn out to be meaningless.  An infection that starts first in the Black community may seem to produce a higher death rate among Blacks but as it spreads out into other communities, the initial difference becomes less and less significant and could even reverse.  Infection rate differences are important to recognize and attack early since they usually relate to factors that could be controlled such as social distancing, crowd control, mask-wearing, hand washing, and testing availability.  There are other factors that affect infection rates that are more difficult to change such as household numbers, housing density, job requirements, etc. but they could still be adjusted.  Factors that affect fatality rates often cannot be changed or are very difficult to change in the short term: age, gender, comorbidities such as obesity, diabetes, and heart disease.  But knowing the scope of these risk factors can help guide the vulnerable population toward less risky and more sheltered and safer behavior.  At the moment it does not seem that the novel coronavirus respects differences in borders, politics, religion, income, fame, or race.