Contacts with environmental biodiversity affect human health: links to allergies, physical and mental health revealed during the initial waves of the COVID-19 pandemic (preprint)

The gradual decrease in the prevalence of serious infectious diseases over the last century has been followed by increase in so called “modern” diseases, including allergies, chronic inflammatory conditions, psychiatric, and metabolic disorders. Between 2019 and 2022, public awareness of the threat of infectious diseases in humans was renewed by the global pandemic of a new type of a coronavirus, the SARS-COV-2. This public interest opened improved possibilities to test hypotheses on the factors associated with inter-individual variation in susceptibility to infectious and “modern” diseases. Based on the Hygiene hypothesis and Biodiversity hypothesis, we predicted that contacts with natural environment and wildlife in childhood and/or in adulthood can improve general health and decrease the risks of severe COVID-19 progression or prevalence of the “modern” diseases, namely the allergies. Here we report the results of an online, self-evaluating questionnaire survey conducted in the Czech Republic, where we contrasted selected health issues, and linked them to the living environment, including the level of contacts with biodiversity. In a sample of 1188 respondents, we revealed a significant effect of time spent in nature and contacts with biodiversity on physical and mental health, and incidence of allergies. This is unlike the COVID-19 progression, which was related to age, physical health, smoking, allergies, and interaction of age with smoking, but not to contacts with the natural environmental diversity. Our findings are in agreement with the Biodiversity hypothesis of allergy and, linking human and environmental health, they urge for One Health approach application.

Is Recovery Just the Beginning? Persistent Symptoms and Health and Performance Deterioration in Post-COVID-19, non-hospitalised University Students - A Cross-Sectional Study (preprint)

Many individuals experience persistent symptoms such as deteriorated physical and mental health, increased fatigue, and reduced cognitive performance months after recovering from COVID-19. Current data are limited on the long-term trajectory of these symptoms and their prevalence in milder cases. Our study aimed to assess the persistent effects of COVID-19 on physical and mental health, fatigue, and cognitive performance in a cohort of 214 students, averaging 21.8 years of age. Of these, 148 had contracted COVID-19 but were not hospitalized, with the time since infection ranging from 1 to 39 months. We utilized a comprehensive panel of cognitive tests to measure intelligence, memory, and psychomotor skills, and a detailed anamnestic questionnaire to evaluate physical and mental health. While contracting COVID-19 did not significantly impact overall health and performance, it was associated with increased reports of fatigue. However, the reported severity of the disease had a pronounced negative influence on physical health, mental well-being, fatigue, and reaction time. Trends of improvement in physical and mental health, as well as error rate, were observed within the first two years post-infection. However, fatigue and reaction time showed a trend of deterioration. Beyond the two-year mark, physical health and error rate continued to improve, while mental health began to deteriorate. Fatigue and reaction time continued to decline. Overall, our findings suggest that some effects of contracting COVID-19 can persist or even deteriorate over time, even in younger individuals who had mild cases that did not require hospitalization.

The Lasting Legacy of COVID-19: Exploring the Long-Term Effects of Infection, Disease Severity, and Vaccination on Health and Cognitive Function (preprint)

COVID-19 affects a variety of organs and systems of the body including the central nervous system. Recent research has shown that COVID-19 survivors often experience neurological and psychological complications that can last for months after infection. We conducted a large internet study using online tests to analyze the effects of SARS-CoV-2 infection, COVID-19 severity, and vaccination on health, intelligence, memory, and information processing precision and speed in a cohort of 4,446 subjects. We found that both SARS-CoV-2 infection and COVID-19 severity were associated with negative impacts on patients health. Furthermore, we observed a negative association between COVID-19 severity and cognitive performance. Younger participants had a higher likelihood of SARS-CoV-2 contraction, while the elderly had a higher likelihood of severe COVID-19 and vaccination. The association between age and COVID-19 severity was primarily mediated by older participants impaired long-term health. Vaccination was positively associated with intelligence and the precision of information processing. However, the positive association between vaccination and intelligence was likely mediated by achieved education, which was itself strongly associated with the likelihood of being vaccinated.

A new and highly effective method for predicting T-cell response targets implemented on SARS-CoV-2 data (preprint)

Computational T-cell epitope prediction is essential in many immunological projects, including the development of vaccines. T-cells of immunocompetent vertebrate hosts can recognize as non-self only peptides which are present in the parasite's proteins and absent in the host's proteins. This basic principle allows us to predict which peptides can elicit T-cells' response. We built on the fact that the specificity of T-cells reacting to SARS-CoV-2 antigens has been recently mapped in detail. Using Monte Carlo tests, we found that empirically confirmed peptides that stimulate T-cells contain an increased fraction of pentapeptides, hexapeptides, and heptapeptides which are not found in the human proteome (p < 0.0001). Similarly, hexapeptides absent in human proteins were overrepresented in peptides that elicited T-cell response in a published empirical study (p = 0.027). The new theory-based method predicted T-cell immunogenicity of SARS-CoV-2 peptides four times more effectively than current empirically based methods.

Effects of 105 biological, socioeconomic, behavioural, and environmental factors on the risk of SARS-CoV-2 infection and a severe course of Covid-19: A prospective longitudinal study (preprint)

The confirmed number of SARS-CoV-2 infections up to 30 August 2021 is 217 mil. worldwide but information about factors affecting the probability of infection or of a severe course of Covid-19 remains insufficient and often speculative. Only a small number of factors have been rigorously examined, mostly by retrospective or cross-sectional studies. We ran a preregistered study on 5,164 internet users who shared with us information about their exposure to 105 risk factors and reported being Covid negative before the beginning of the fourth wave of Covid-19 in the Czech Republic. After the fourth wave, in which 709 (13.7%) of participants were infected, we used a partial Kendall test controlled for sex, age, and urbanisation to compare the risk of infection and of a severe course of the disease in subjects who originally did and did not report exposure to particular risk factors. After the correction for multiple tests, we identified 13 factors - including male sex, lower age, blood group B, and the larger household size - that increased the risk of infection and 16 factors - including mask wearing, borreliosis in the past, use of vitamin D supplements, or rooibos drinking - that decreased it. We also identified 23 factors that increased the risk of a severe course of Covid-19 and 12 factors that decreased the risk.

Toxoplasmosis is a Risk Factor for Acquiring SARS-CoV-2 Infection and a Severe Course of Covid-19 Disease in The Czech and Slovak Population: A Preregistered Exploratory Internet Cross-Sectional Study (preprint)

Background: Latent toxoplasmosis, i.e. a lifelong infection with the protozoan parasite Toxoplasma gondii , affects about a third of human population worldwide. In the past ten years, numerous studies had shown that infected subjects have a significantly higher incidence of mental and physical health problems and are more prone to exhibiting the adverse effects of various diseases. Methods A cross-sectional internet study was performed on a population of 4,499 (786 Toxoplasma -infected) subjects and looked for factors which positively or negatively affect the risk of SARS-CoV-2 infection and likelihood of a severe course of Covid-19. Results Logistic regression and partial Kendall correlation controlled for sex, age, and size of the place of residence showed that latent toxoplasmosis had the strongest effect on the risk of infection (OR = 1·50) before sport (OR = 1·30), and borreliosis (1·27). It also had the strongest effect on the risk of severe course of infection (Tau = 0·146), before autoimmunity, immunodeficiency, male sex, keeping a cat, being overweight, borreliosis, higher age, or chronic obstructive pulmonary disease. Toxoplasmosis augmented the adverse effects of other risk factors but was not the proximal cause of the effect of cat keeping on higher likelihood of Covid infection and higher severity of the course of infection because the effect of cat keeping was observed also (and especially) in a subset of Toxoplasma -infected subjects (Tau = 0·153). Effects of keeping a cat were detected only in subjects from multi-member families, suggesting that a cat could a vector for the transmission of SARS-CoV-2 within a family. Conclusions Toxoplasmosis is currently not considered a risk factor for Covid-19 and Toxoplasma -infected subjects are neither informed about their higher risks nor prioritised in vaccination programs. Because toxoplasmosis affects a large segment of the human population, its impact on Covid-19-associated effects on public health could be considerable.

Toxoplasmosis: An important risk factor for acquiring SARS-CoV-2 infection and a severe course of Covid-19 disease, a cross-sectional study (preprint)

Background Latent toxoplasmosis, i.e. a lifelong infection with the protozoan parasite Toxoplasma gondii, affects about a third of human population worldwide. In the past ten years, numerous studies had shown that infected subjects have a significantly higher incidence of mental and physical health problems and are more prone to exhibiting the adverse effects of various diseases. Methods A cross-sectional internet study was performed on a population of 4,499 Toxoplasma-free and 786 Toxoplasma-infected subjects and looked for factors which positively or negatively affect the risk of SARS-CoV-2 infection and likelihood of a severe course of Covid-19. Results Logistic regression and partial Kendall correlation controlled for sex, age, and size of the place of residence showed that latent toxoplasmosis had the strongest effect on the risk of infection (OR = 1·50) before sport (OR = 1·30), and borreliosis (1·27). It also had the strongest effect on the risk of severe course of infection (Tau = 0·146), before autoimmunity, immunodeficiency, male sex, keeping a cat, being overweight, borreliosis, higher age, or chronic obstructive pulmonary disease. Toxoplasmosis augmented the adverse effects of other risk factors but was not the proximal cause of the effect of cat keeping (in the form of higher likelihood of Covid infection and higher severity of the course of infection), which was observed especially in a subset of Toxoplasma-infected subjects (Tau = 0·153). Effects of keeping a cat were detected only in subjects from multi-member families, suggesting that a cat could a vector for the transmission of SARS-CoV-2 within a family. Conclussions Toxoplasmosis is currently not considered a risk factor for Covid-19 and Toxoplasma-infected subjects are neither informed about their higher risks nor prioritised in vaccination programs. Because toxoplasmosis affects a large segment of the human population, its impact on Covid-19-associated effects on public health could be considerable.

Toxoplasmosis: An important risk factor for acquiring SARS-CoV-2 infection and a severe course of Covid-19 disease (preprint)

Background Latent toxoplasmosis, i.e. a lifelong infection with the protozoan parasite Toxoplasma gondii, affects about a third of human population worldwide. In the past ten years, numerous studies had shown that infected subjects have a significantly higher incidence of mental and physical health problems and are more prone to exhibiting the adverse effects of various diseases. Methods A cross-sectional internet study was performed on a population of 4,499 Toxoplasma-free and 786 Toxoplasma-infected subjects and looked for factors which positively or negatively affect the risk of SARS-CoV-2 infection and likelihood of a severe course of Covid-19. Findings Logistic regression and partial Kendall correlation controlled for sex, age, and size of the place of residence showed that latent toxoplasmosis had the strongest effect on the risk of infection (OR = 1.50) before sport (OR = 1.30), and borreliosis (1.27). It also had the strongest effect on the risk of severe course of infection (Tau = 0.146), before autoimmunity, immunodeficiency, male sex, keeping a cat, being overweight, borreliosis, higher age, or chronic obstructive pulmonary disease. Toxoplasmosis augmented the adverse effects of other risk factors but was not the proximal cause of the effect of cat keeping (in the form of higher likelihood of Covid infection and higher severity of the course of infection), which was observed especially in a subset of Toxoplasma-infected subjects (Tau = 0.153). Effects of keeping a cat were detected only in subjects from multi-member families, suggesting that a cat could a vector for the transmission of SARS-CoV-2 within a family. Interpretations Toxoplasmosis is currently not considered a risk factor for Covid-19 and Toxoplasma-infected subjects are neither informed about their higher risks nor prioritised in vaccination programs. Because toxoplasmosis affects a large segment of the human population, its impact on Covid-19-associated effects on public health could be considerable.