Asthmatic patients in COVID-19 outbreak: Few cases despite many cases

To the Editor:

We read with great interest the article “Risk factors for severity and mortality in adult COVID-19 inpatients in Wuhan” by Li et al,¹ one of the most detailed studies in terms of patients’ clinical characterization.

Interestingly, the reported asthma prevalence among patients with coronavirus disease 2019 (COVID-19) admitted to hospital was 0.9%, extremely lower than in the general population (6.4%): this is clearly unexpected because bronchial inflammation is associated with an increased susceptibility to viral infections.² It has been hypothesized that in the case of COVID-19, inhaled corticosteroid treatment could modulate that susceptibility,³ although at the moment the relationship between COVID-19 and asthma remains unclear.⁴ In this context, asthma prevalence in the general population and the impact of COVID-19 outbreak in a specific area may condition the proportion of affected patients with asthma.⁵ Furthermore, asthma has been not specifically reported or investigated as a risk factor.⁵

We revised the COVID-19 cases (Table I ) admitted in the period between March 1 and April 30, 2020, to 2 major hospitals placed in Verona (Veneto region) and Brescia (Lombardia region), in the North-east of Italy, one of the most affected areas in Europe.⁶ Verona and Brescia are neighboring cities, and Brescia has a greater population density. This last aspect may have conditioned the deeply different impact of COVID-19 infection in the 2 cities in terms of total amount of infected subjects and patients needing hospitalization.⁷ Surprisingly, we observed that the weight of hospital admission due to COVID-19 in patients with asthma (confirmed diagnosis by National Health System exemption code) is very similar in Verona and Brescia (1.96% and 1.92%, respectively), as well as the prevalence in the general population in the 2 areas (6%). According to the prescribed inhaled treatment, 5 of 6 patients with asthma from Verona suffered from moderate asthma; the other one, together with 15 of 20 from Brescia, was affected by mild asthma and all reported an optimal adherence rate. The other 5 cases in Brescia were affected by mild-intermittent asthma. None of the subjects reported asthma exacerbation before the admission to hospital. Mild obesity, presence of nonsevere cardiovascular diseases, and active smoking habit characterized 14 (70%) of 20 patients with asthma in Brescia Hospital, whereas in Verona 3 (50%) of 6 patients were affected by hypertension and another one by obesity and diabetes. In Verona, no one was a current smoker.

Table I.

Data related to the COVID-19 outbreak in Verona and Brescia, up to April 30, 2020

Epidemiological and COVID-19 related features of the study population	Brescia	Verona
Population	198,536	257,993
Population density (people per km2)	2,197.77	1,296.99
People tested by swabs	216,526 (Lombardia region)	196,864 (Veneto region)
People positive to SARS-CoV-2	12,861	4,679
Patients admitted because of COVID-19, n (%)	1,043 (8.1% of positive cases)	305 (6.5% of positive cases)
Patients with asthma among patients admitted because of COVID-19, n (%)	20 (1.92%) 12 F, 8 M Age range: 41-77 y (mean, 61.5 y)	6 (1.96%) 3 F, 3 M Age range: 55-79 y (mean, 69.3 y)
Prevalence of asthma in the general population	6.1%	6.0%

F, Female; M, male; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Similarly to the Wuhan report,¹ our observation, the first in the Italian population, highlights that the hospitalization rate due to COVID-19 in patients with asthma is extremely low, and consistent with the asthma prevalence in the general population, more than with the size of the viral outbreak. This finding supports the unexpected hypothesis that asthma itself cannot be considered a risk factor for susceptibility to COVID-19. Which is the missing link?