Pollen exposure weakens innate defense against respiratory viruses

Increasing prevalence and influencing factors of childhood asthma: a cross-sectional study in Shanghai, China

BACKGROUND

Asthma has been a global problem, especially in children. We aim to evaluate the contemporary prevalence and influencing factors of asthma among children aged 3-7 years in Shanghai, China.

METHODS

A random sample of preschool children was included in this study. The International Study of Asthma and Allergies in Childhood questionnaire was adopted to assess the childhood asthma. Multivariable logistic regression models were used to evaluate the associations between independent variables and childhood asthma.

RESULTS

Of 6389 preschool children who were invited to take part in this study, 6163 (response rate: 96.5%) completed the questionnaire and were included in the analysis. The overall prevalence of asthma was 14.6% which increased more than six folds from 2.1% in 1990. Being male, younger age, preterm delivery, being born in spring or autumn, being delivered by elective cesarean section without indication, miscarriage, high socioeconomic status, having allergy history, and exposure to passive smoking, latex paint, and dust were potential risk factors for childhood asthma. Spending more time outdoors (> 30 min/day), having indoor plants, and cleaning rooms more frequently were potential protective factors.

CONCLUSIONS

The prevalence of childhood asthma in Shanghai has increased dramatically during the past three decades. The findings about risk and protective factors of childhood asthma could be used to develop appropriate strategies to prevent and control childhood asthma in Shanghai and in other similar metropolitan cities.

Anthropogenic climate change is worsening North American pollen seasons

Human-caused climate change could impact respiratory health, including asthma and allergies, through temperature-driven increases in airborne pollen, but the long-term continental pollen trends and role of climate change in pollen patterns are not well-understood. We measure pollen trends across North America from 1990 to 2018 and find increases in pollen concentrations and longer pollen seasons. We use an ensemble of climate models to test the role of climate change and find that it is the dominant driver of changes in pollen season length and a significant contributor to increasing pollen concentrations. Our results indicate that human-caused climate change has already worsened North American pollen seasons, and climate-driven pollen trends are likely to further exacerbate respiratory health impacts in coming decades.

Airborne pollen has major respiratory health impacts and anthropogenic climate change may increase pollen concentrations and extend pollen seasons. While greenhouse and field studies indicate that pollen concentrations are correlated with temperature, a formal detection and attribution of the role of anthropogenic climate change in continental pollen seasons is urgently needed. Here, we use long-term pollen data from 60 North American stations from 1990 to 2018, spanning 821 site-years of data, and Earth system model simulations to quantify the role of human-caused climate change in continental patterns in pollen concentrations. We find widespread advances and lengthening of pollen seasons (+20 d) and increases in pollen concentrations (+21%) across North America, which are strongly coupled to observed warming. Human forcing of the climate system contributed ∼50% (interquartile range: 19–84%) of the trend in pollen seasons and ∼8% (4–14%) of the trend in pollen concentrations. Our results reveal that anthropogenic climate change has already exacerbated pollen seasons in the past three decades with attendant deleterious effects on respiratory health.

The need for Pan-European automatic pollen and fungal spore monitoring: A stakeholder workshop position paper

Background

Information about airborne pollen concentrations is required by a range of end users, particularly from the health sector who use both observations and forecasts to diagnose and treat allergic patients. Manual methods are the standard for such measurements but, despite the range of pollen taxa that can be identified, these techniques suffer from a range of drawbacks. This includes being available at low temporal resolution (usually daily averages) and with a delay (usually 3–9 days from the measurement). Recent technological developments have made possible automatic pollen measurements, which are available at high temporal resolution and in real time, although currently only scattered in a few locations across Europe.

Materials & Methods

To promote the development of an extensive network across Europe and to ensure that this network will respond to end user needs, a stakeholder workshop was organised under the auspices of the EUMETNET AutoPollen Programme. Participants discussed requirements for the groups they represented, ranging from the need for information at various spatial scales, at high temporal resolution, and for targeted services to be developed.

Results

The provision of real‐time information is likely to lead to a notable decrease in the direct and indirect health costs associated with allergy in Europe, currently estimated between €50–150 billion/year.¹

Discussion & Conclusion

A European measurement network to meet end user requirements would thus more than pay for itself in terms of potential annual savings and provide significant impetus to research across a range of disciplines from climate science and public health to agriculture and environmental management.

Coronavirus disease 2019, allergic diseases, and allergen immunotherapy: Possible favorable mechanisms of interaction

Background: Both, allergen immunotherapy (AIT) and SARS-COV-2 infection cause a set of immunologic changes that respectively vary during the course of the treatment or the disease. Objective: To review immune changes brought along by each of these entities and how they might interrelate. Methods: We start presenting a brief review of the structure of the new coronavirus and how it alters the functioning of the human immune system. Subsequently, we describe the immune changes induced by AIT and how these changes could be favorable or unfavorable in the allergic patient infected with SARS-CoV-2 at a particular point of time during the evolving infection. Results: We describe how a healthy immune response against SARS-CoV-2 develops, versus an immune response that is initially suppressed by the virus, but ultimately overactivated, leading to an excessive production of cytokines (cytokine-storm-like). These changes are then linked to the clinical manifestations and outcomes of the patient. Reviewing the immune changes secondary to AIT, it becomes clear how AIT is capable of restoring a healthy innate immunity. Investigators have previously shown that the frequency of respiratory infections is reduced in allergic patients treated with AIT. On the other hand it also increases immunoregulation. Conclusion: As there are many variables involved, it is hard to predict how AIT could influence the allergic patient's reaction to a SARS-CoV-2 infection. In any case, AIT is likely to be beneficial for the patient with allergic rhinitis and/or allergic asthma in the context of the SARS-CoV-2 pandemic as controlling allergic diseases leads to a reduced need for contact with healthcare professionals. The authors remind the reader that everything in this article is still theoretical, since at the moment, there are no published clinical trials on the outcome of COVID-19 in allergic patients under AIT.

Higher airborne pollen concentrations correlated with increased SARS-CoV-2 infection rates, as evidenced from 31 countries across the globe

Pollen exposure weakens the immunity against certain seasonal respiratory viruses by diminishing the antiviral interferon response. Here we investigate whether the same applies to the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is sensitive to antiviral interferons, if infection waves coincide with high airborne pollen concentrations. Our original hypothesis was that more airborne pollen would lead to increases in infection rates. To examine this, we performed a cross-sectional and longitudinal data analysis on SARS-CoV-2 infection, airborne pollen, and meteorological factors. Our dataset is the most comprehensive, largest possible worldwide from 130 stations, across 31 countries and five continents. To explicitly investigate the effects of social contact, we additionally considered population density of each study area, as well as lockdown effects, in all possible combinations: without any lockdown, with mixed lockdown-no lockdown regime, and under complete lockdown. We found that airborne pollen, sometimes in synergy with humidity and temperature, explained, on average, 44% of the infection rate variability. Infection rates increased after higher pollen concentrations most frequently during the four previous days. Without lockdown, an increase of pollen abundance by 100 pollen/m3 resulted in a 4% average increase of infection rates. Lockdown halved infection rates under similar pollen concentrations. As there can be no preventive measures against airborne pollen exposure, we suggest wide dissemination of pollen-virus coexposure dire effect information to encourage high-risk individuals to wear particle filter masks during high springtime pollen concentrations.

No SARS-CoV-2 detected in air samples (pollen and particulate matter) in Leipzig during the first spread

The SARS-CoV-2 pandemic co-occurred with pollen season in Europe 2020 and recent studies suggest a potential link between both. Air samples collected at our measuring station in Leipzig and purified pollen were analyzed for SARS-CoV-2 typical signals or for virus-induced cytopathic effects, to test if the virus could bind to bioaerosols and if so, whether these complexes are infectious. The results show that neither our air samples nor purified pollen were infectious or could act as carrier for virus particles.

Can pollen explain the seasonality of flu-like illnesses in the Netherlands?

Current models for flu-like epidemics insufficiently explain multi-cycle seasonality. Meteorological factors alone, including the associated behavior, do not predict seasonality, given substantial climate differences between countries that are subject to flu-like epidemics or COVID-19. Pollen is documented to be allergenic, it plays a role in immuno-activation and defense against respiratory viruses, and seems to create a bio-aerosol that lowers the reproduction number of flu-like viruses. Therefore, we hypothesize that pollen may explain the seasonality of flu-like epidemics, including COVID-19, in combination with meteorological variables. We have tested the Pollen-Flu Seasonality Theory for 2016-2020 flu-like seasons, including COVID-19, in the Netherlands, with its 17.4 million inhabitants. We combined changes in flu-like incidence per 100 K/Dutch residents (code: ILI) with pollen concentrations and meteorological data. Finally, a predictive model was tested using pollen and meteorological threshold values, inversely correlated to flu-like incidence. We found a highly significant inverse correlation of r(224) = -0.41 (p < 0.001) between pollen and changes in flu-like incidence, corrected for the incubation period. The correlation was stronger after taking into account the incubation time. We found that our predictive model has the highest inverse correlation with changes in flu-like incidence of r(222) = -0.48 (p < 0.001) when average thresholds of 610 total pollen grains/m³, 120 allergenic pollen grains/m³, and a solar radiation of 510 J/cm² are passed. The passing of at least the pollen thresholds, preludes the beginning and end of flu-like seasons. Solar radiation is a co-inhibitor of flu-like incidence, while temperature makes no difference. However, higher relative humidity increases with flu-like incidence. We conclude that pollen is a predictor of the inverse seasonality of flu-like epidemics, including COVID-19, and that solar radiation is a co-inhibitor, in the Netherlands.

Clinical characteristics of 182 pediatric COVID-19 patients with different severities and allergic status

Background

The pandemic of coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection has made widespread impact recently. We aim to investigate the clinical characteristics of COVID‐19 children with different severities and allergic status.

Methods

Data extracted from the electronic medical records, including demographics, clinical manifestations, comorbidities, laboratory and immunological results, and radiological images of 182 hospitalized COVID‐19 children, were summarized and analyzed.

Results

The median age was 6 years, ranging from 3 days to 15 years, and there were more boys (male‐female ratio about 2:1) within the studied 182 patients. Most of the children were infected by family members. Fever (43.4%) and dry cough (44.5%) were common symptoms, and gastrointestinal manifestations accounted for 11.0%, including diarrhea, abdominal discomfort, and vomiting. 71.4% had abnormal chest computed tomography (CT) scan images, and typical signs of pneumonia were ground‐glass opacity and local patchy shadowing on admission. Laboratory results were mostly within normal ranges, and only a small ratio of lymphopenia (3.9%) and eosinopenia (29.5%) were observed. The majority (97.8%) of infected children were not severe, and 24 (13.2%) of them had asymptomatic infections. Compared to children without pneumonia (manifested as asymptomatic and acute upper respiratory infection), children with pneumonia were associated with higher percentages of the comorbidity history, symptoms of fever and cough, and increased levels of serum procalcitonin, alkaline phosphatase, and serum interleukins (IL)‐2, IL‐4, IL‐6, IL‐10, and TNF‐α. There were no differences in treatments, duration of hospitalization, time from first positive to first negative nucleic acid testing, and outcomes between children with mild pneumonia and without pneumonia. All the hospitalized COVID‐19 children had recovered except one death due to intussusception and sepsis. In 43 allergic children with COVID‐19, allergic rhinitis (83.7%) was the major disease, followed by drug allergy, atopic dermatitis, food allergy, and asthma. Demographics and clinical features were not significantly different between allergic and nonallergic groups. Allergic patients showed less increase in acute phase reactants, procalcitonin, D‐dimer, and aspartate aminotransferase levels compared with all patients. Immunological profiles including circulating T, B, and NK lymphocyte subsets, total immunoglobulin and complement levels, and serum cytokines did not show any difference in allergic and pneumonia groups. Neither eosinophil counts nor serum total immunoglobulin E (IgE) levels showed a significant correlation with other immunological measures, such as other immunoglobulins, complements, lymphocyte subset numbers, and serum cytokine levels.

Conclusion

Pediatric COVID‐19 patients tended to have a mild clinical course. Patients with pneumonia had higher proportion of fever and cough and increased inflammatory biomarkers than those without pneumonia. There was no difference between allergic and nonallergic COVID‐19 children in disease incidence, clinical features, and laboratory and immunological findings. Allergy was not a risk factor for developing and severity of SARS‐CoV‐2 infection and hardly influenced the disease course of COVID‐19 in children.

Assessment and statistical modelling of airborne microorganisms in Madrid

The limited evidence available suggests that the interaction between chemical pollutants and biological particles may intensify respiratory diseases caused by air pollution in urban areas. Unlike air pollutants, which are routinely measured, records of biotic component are scarce. While pollen concentrations are daily surveyed in most cities, data related to airborne bacteria or fungi are not usually available. This work presents the first effort to understand atmospheric pollution integrating both biotic and abiotic agents, trying to identify relationships among the Proteobacteria, Actinobacteria and Ascomycota phyla with palynological, meteorological and air quality variables using all biological historical records available in the Madrid Greater Region. The tools employed involve statistical hypothesis contrast tests such as Kruskal-Wallis and machine learning algorithms. A cluster analysis was performed to analyse which abiotic variables were able to separate the biotic variables into groups. Significant relationships were found for temperature and relative humidity. In addition, the relative abundance of the biological phyla studied was affected by PM₁₀ and O₃ ambient concentration. Preliminary Generalized Additive Models (GAMs) to predict the biotic relative abundances based on these atmospheric variables were developed. The results (r = 0.70) were acceptable taking into account the scarcity of the available data. These models can be used as an indication of the biotic composition when no measurements are available. They are also a good starting point to continue working in the development of more accurate models and to investigate causal relationships.

Synergistic health effects of air pollution, temperature, and pollen exposure: a systematic review of epidemiological evidence

BACKGROUND

Exposure to heat, air pollution, and pollen are associated with health outcomes, including cardiovascular and respiratory disease. Studies assessing the health impacts of climate change have considered increased exposure to these risk factors separately, though they may be increasing simultaneously for some populations and may act synergistically on health. Our objective is to systematically review epidemiological evidence for interactive effects of multiple exposures to heat, air pollution, and pollen on human health.

METHODS

We systematically searched electronic literature databases (last search, April 29, 2019) for studies reporting quantitative measurements of associations between at least two of the exposures and mortality from any cause and cardiovascular and respiratory morbidity and mortality specifically. Following the Navigation Guide systematic review methodology, we evaluated the risk of bias of individual studies and the overall quality and strength of evidence.

RESULTS

We found 56 studies that met the inclusion criteria. Of these, six measured air pollution, heat, and pollen; 39 measured air pollution and heat; 10 measured air pollution and pollen; and one measured heat and pollen. Nearly all studies were at risk of bias from exposure assessment error. However, consistent exposure-response across studies led us to conclude that there is overall moderate quality and sufficient evidence for synergistic effects of heat and air pollution. We concluded that there is overall low quality and limited evidence for synergistic effects from simultaneous exposure to (1) air pollution, pollen, and heat; and (2) air pollution and pollen. With only one study, we were unable to assess the evidence for synergistic effects of heat and pollen.

CONCLUSIONS

If synergistic effects between heat and air pollution are confirmed with additional research, the health impacts from climate change-driven increases in air pollution and heat exposure may be larger than previously estimated in studies that consider these risk factors individually.

Biomarkers for diagnosis and prediction of therapy responses in allergic diseases and asthma

Modern health care requires a proactive and individualized response to diseases, combining precision diagnosis and personalized treatment. Accordingly, the approach to patients with allergic diseases encompasses novel developments in the area of personalized medicine, disease phenotyping and endotyping, and the development and application of reliable biomarkers. A detailed clinical history and physical examination followed by the detection of IgE immunoreactivity against specific allergens still represents the state of the art. However, nowadays, further emphasis focuses on the optimization of diagnostic and therapeutic standards and a large number of studies have been investigating the biomarkers of allergic diseases, including asthma, atopic dermatitis, allergic rhinitis, food allergy, urticaria and anaphylaxis. Various biomarkers have been developed by omics technologies, some of which lead to a better classification of distinct phenotypes or endotypes. The introduction of biologicals to clinical practice increases the need for biomarkers for patient selection, prediction of outcomes and monitoring, to allow for an adequate choice of the duration of these costly and long‐lasting therapies. Escalating healthcare costs together with questions about the efficacy of the current management of allergic diseases require further development of a biomarker‐driven approach. Here, we review biomarkers in diagnosis and treatment of asthma, atopic dermatitis, allergic rhinitis, viral infections, chronic rhinosinusitis, food allergy, drug hypersensitivity and allergen immunotherapy with a special emphasis on specific IgE, the microbiome and the epithelial barrier. In addition, EAACI guidelines on biologicals are discussed within the perspective of biomarkers.

Recent updates on COVID-19: A holistic review

Coronaviruses are large positive-sense RNA viruses with spike-like peplomers on their surface. The Coronaviridae family's strains infect different animals and are popularly associated with several outbreaks, namely SARS and MERS epidemic. COVID-19 is one such recent outbreak caused by SARS-CoV-2 identified first in Wuhan, China. COVID-19 was declared a pandemic by WHO on 11th March 2020. Our review provides information covering various facets of the disease starting from its origin, transmission, mutations in the virus to pathophysiological changes in the host upon infection followed by diagnostics and possible therapeutics available to tackle the situation. We have highlighted the zoonotic origin of SARS-CoV-2, known to share 96.2% nucleotide similarity with bat coronavirus. Notably, several mutations in SARS-CoV-2 spike protein, nucleocapsid protein, PLpro, and ORF3a are reported across the globe. These mutations could alter the usual receptor binding function, fusion process with the host cell, virus replication, and the virus's assembly. Therefore, studying these mutations could help understand the virus's virulence properties and design suitable therapeutics. Moreover, the aggravated immune response to COVID-19 can be fatal. Hypertension, diabetes, and cardiovascular diseases are comorbidities substantially associated with SARS-CoV-2 infection. The review article discusses these aspects, stating the importance of various comorbidities in disease outcomes. Furthermore, medications' unavailability compels the clinicians to opt for atypical drugs like remdesivir, chloroquine, etc. The current diagnostics of COVID-19 include qRT-PCR, CT scan, serological tests, etc. We have described these aspects to expose the information to the scientific community and to accelerate the research.

Spatiotemporal characteristics of asthma emergency department presentations in diverse geographical and climatic regions, Queensland, Australia

OBJECTIVE

Sudden acute episodes of asthma exacerbation are often treated by hospital EDs. It is hypothesised that determinants of acute asthma would differ across geographic regions. The objective of the present study was to detail seasonality, trends and spatiotemporal patterns of asthma ED presentations across Queensland (QLD), Australia, a state covering 1.8 million square kilometres, spanning multiple climates.

METHODS

Six years of routinely collected data (2012 to 2017) from 28 major QLD public hospitals were extracted from Queensland Health's Emergency Data Collection. The dataset contained individual, episode-level asthma-like diagnoses of ED presentations. Seasonality and trends of acute asthma were assessed through multiplicative time-series analysis.

RESULTS

The study consisted of 2192 days with a total of 65 012 asthma ED presentations in QLD. The 6-year average daily incidence rate was 270 asthma ED presentations per 100 000 population. The highest morbidity of asthma ED presentations occurred during the southern hemisphere winter months. Children showed a higher incidence rate compared to adults with males experiencing a higher incidence compared to females up until the age of 13, after which an inversion was observed persisting through adulthood. Seasonality of asthma ED presentations differed with latitude across QLD.

CONCLUSION

Asthma-related ED presentations exhibit spatiotemporal variation across QLD, which appears to be related to climate. Furthermore, aeroallergens and respiratory viruses may be responsible for asthma ED peaks outside the winter period. Socioeconomic status may influence asthma ED presentation rates between regions. This knowledge can guide ongoing management and assist public health policy response.

Allergenic Pollen Season Variations in the Past Two Decades Under Changing Climate in the United States

Prevalence of allergic diseases has been increasing due to multiple factors, among which climate change has had the most impact. Climate factors increase production of pollen, which also exhibits increased allergenicity. Also, as a result of climate change, there has been a shift in flowering phenology and pollen initiation causing prolonged pollen exposure. Various numerical models have been developed to understand the effect of climate change on pollen emission and transport and the impact on allergic airway diseases.

SARS-CoV-2 Pneumonia in Hospitalized Asthmatic Patients Did Not Induce Severe Exacerbation

BACKGROUND

Viral infections are known to exacerbate asthma in adults. Previous studies have found few patients with asthma among severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia cases. However, the relationship between SARS-CoV-2 infection and severe asthma exacerbation is not known.

OBJECTIVE

To assess the frequency of asthma exacerbation in patients with asthma hospitalized for SARS-CoV-2 pneumonia and compare symptoms and laboratory and radiological findings in patients with and without asthma with SARS-CoV-2 pneumonia.

METHODS

We included 106 patients between March 4 and April 6, 2020, who were hospitalized in the Chest Diseases Department of Strasbourg University Hospital; 23 had asthma. To assess the patients' asthma status, 3 periods were defined: the last month before the onset of COVID-19 symptoms (p1), prehospitalization (p2), and during hospitalization (p3). Severe asthma exacerbations were defined according to Global INitiative for Asthma guidelines during p1 and p2. During p3, we defined severe asthma deterioration as the onset of breathlessness and wheezing requiring systemic corticosteroids and inhaled β2 agonist.

RESULTS

We found no significant difference between patients with and without asthma in terms of severity (length of stay, maximal oxygen flow needed, noninvasive ventilation requirement, and intensive care unit transfer); 52.2% of the patients with asthma had Global INitiative for Asthma step 1 asthma. One patient had a severe exacerbation during p1, 2 patients during p2, and 5 patients were treated with systemic corticosteroids and inhaled β2 agonist during p3.

CONCLUSIONS

Our results demonstrate that patients with asthma appeared not to be at risk for severe SARS-CoV-2 pneumonia. Moreover, SARS-CoV-2 pneumonia did not induce severe asthma exacerbation.

Clinical characteristics of 140 patients infected with SARS-CoV-2 in Wuhan, China

BACKGROUND

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been widely spread. We aim to investigate the clinical characteristic and allergy status of patients infected with SARS-CoV-2.

METHODS

Electronic medical records including demographics, clinical manifestation, comorbidities, laboratory data, and radiological materials of 140 hospitalized COVID-19 patients, with confirmed result of SARS-CoV-2 viral infection, were extracted and analyzed.

RESULTS

An approximately 1:1 ratio of male (50.7%) and female COVID-19 patients was found, with an overall median age of 57.0 years. All patients were community-acquired cases. Fever (91.7%), cough (75.0%), fatigue (75.0%), and gastrointestinal symptoms (39.6%) were the most common clinical manifestations, whereas hypertension (30.0%) and diabetes mellitus (12.1%) were the most common comorbidities. Drug hypersensitivity (11.4%) and urticaria (1.4%) were self-reported by several patients. Asthma or other allergic diseases were not reported by any of the patients. Chronic obstructive pulmonary disease (COPD, 1.4%) patients and current smokers (1.4%) were rare. Bilateral ground-glass or patchy opacity (89.6%) was the most common sign of radiological finding. Lymphopenia (75.4%) and eosinopenia (52.9%) were observed in most patients. Blood eosinophil counts correlate positively with lymphocyte counts in severe (r = .486, P < .001) and nonsevere (r = .469, P < .001) patients after hospital admission. Significantly higher levels of D-dimer, C-reactive protein, and procalcitonin were associated with severe patients compared to nonsevere patients (all P < .001).

CONCLUSION

Detailed clinical investigation of 140 hospitalized COVID-19 cases suggests eosinopenia together with lymphopenia may be a potential indicator for diagnosis. Allergic diseases, asthma, and COPD are not risk factors for SARS-CoV-2 infection. Older age, high number of comorbidities, and more prominent laboratory abnormalities were associated with severe patients.

Eleven faces of coronavirus disease 2019

Background and aims

The outbreak of coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection has recently spread worldwide and been declared a pandemic. We aim to describe here the various clinical presentations of this disease by examining eleven cases.

Methods

Electronic medical records of 11 patients with COVID‐19 were collected, and demographics, clinical manifestations, outcomes, key laboratory results, and radiological images are discussed.

Results

The clinical course of the eleven cases demonstrated the complexity of the COVID‐19 profile with different clinical presentations. Clinical manifestations range from asymptomatic cases to patients with mild and severe symptoms, with or without pneumonia. Laboratory detection of the viral nucleic acid can yield false‐negative results, and serological testing of virus‐specific IgG and IgM antibodies should be used as an alternative for diagnosis. Patients with common allergic diseases did not develop distinct symptoms and severe courses. Cases with a pre‐existing condition of chronic obstructive pulmonary disease or complicated with a secondary bacterial pneumonia were more severe.

Conclusion

All different clinical characteristics of COVID‐19 should be taken into consideration to identify patients that need to be in strict quarantine for the efficient containment of the pandemic.