A study by researchers at Bicêtre Hospital, on patients hospitalised for COVID-19, has shown that asthmatics do not present an increased risk of developing a severe form of the disease.
Infections related to respiratory tropism viruses (rhinovirus, respiratory syncytial virus, influenza viruses, etc.) are the main cause of asthma exacerbation and may be associated with severe respiratory episodes in asthmatic patients.
Several pathophysiological mechanisms have been put forward to explain this susceptibility to viral infections in asthmatics, first and foremost the role of type 2 inflammation (characterised by a predominant production of interleukins 4, 5 and 13, which promote eosinophilic and allergic reactions), which is believed to reduce innate immune responses and particularly the synthesis of the various types of interferons essential to the antiviral response.
The outbreak of COVID-19, related to the SARS-CoV-2 coronavirus, characterised in its severe forms by severe pneumonia leading to a potentially fatal acute respiratory distress syndrome, could raise concerns about an increased risk of severe forms in asthmatics. Indeed, the respiratory tropism of coronaviruses is well known and some of them have already been involved in epidemics of severe pneumopathies such as SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome).
In a general review published in 2018, prior to the emergence of CoV-2-SARS, the detection of a coronavirus in respiratory specimens during an asthma flare-up ranged from 8.4% in children to 20.8% in adults, making this family of viruses the second most common virus identified in adults after rhinoviruses and the fourth most common in children after rhinoviruses, respiratory syncytial virus and enteroviruses. Thus, there was concern that the current epidemic may be accompanied by an increased risk of SARS-CoV-2 coronavirus infection in asthmatics associated with severe lung disease and/or asthmatic flare-ups.
Curiously, however, in the first publications, whether in China, Italy or the USA, asthma patients do not appear to be over-represented, especially considering the prevalence of asthma estimated at between 7 and 10% depending on the country.
The objective of the researchers from Bicêtre Hospital, AP-HP / Faculty of Medicine at Paris-Saclay University was to describe the clinical characteristics and the fate of asthma patients hospitalised for COVID-19 pneumopathy in the spring of 2020 at Bicêtre Hospital.
In a group of 768 patients hospitalised from 15 March to 15 April 2020, 37 (4.8%) were asthmatic, a proportion broadly similar to the general population of the same age in France. These patients were younger than non-asthmatic patients hospitalised for COVID-19 pneumopathy and more often female.
It is noteworthy that none of these patients experienced a severe asthma attack warranting specific treatment on admission to hospital, confirming that this respiratory infection is less likely to exacerbate asthma than other respiratory viral infections. Furthermore, there is no evidence to suggest increased illness or mortality in these patients. Treatment of asthma was generally not altered during hospitalisation, noting that continued treatment does not appear to be detrimental in patients with asthma infected with CoV-2-SARS.
Further studies are underway to test the hypothesis that treatment of asthma may be beneficial during COVID-19. This study shows that asthmatics are not over-represented in a cohort of patients hospitalised for severe lung disease related to CoV-2-SARS, that mortality in infected asthma patients is not increased compared to the general population, and that asthma treatment should be maintained in these patients.
The research was published in the European Respiratory Journal.