A Decrease in Temperature and Humidity Precedes Human Rhinovirus Infections in a Cold Climate

Indoor air humidity revisited: Impact on acute symptoms, work productivity, and risk of influenza and COVID-19 infection

Recent epidemiological and experimental findings reconfirm that low indoor air humidity (dry air) increases the prevalence of acute eye and airway symptoms in offices, result in lower mucociliary clearance in the airways, less efficient immune defense, and deteriorate the work productivity. New epidemiological and experimental research also support that the environmental conditions for the risk of infection of influenza and COVID-19 virus is lowest in the Goldilocks zone of 40-60% relative humidity (RH) by decrease of the airways' susceptibility, which can be elevated by particle exposure. Furthermore, low RH increases the generation of infectious virus laden aerosols exhaled from infected people. In general, elevation of the indoor air humidity from dry air increases the health of the airways concomitantly with lower viability of infectious virus. Thus, the negative effects of ventilation with dry outdoor air (low absolute air humidity) should be assessed according to 1) weakened health and functionality of the airways, 2) increased viability and possible increased transmissibility of infectious virus, and 3) evaporation of virus containing droplets to dry out to droplet nuclei (also possible at high room temperature), which increases their floating time in the indoor air. The removal of acid-containing ambient aerosols from the indoor air by filtration increases pH, viability of infectious viruses, and the risk of infection, which synergistically may further increase by particle exposure. Thus, the dilution of indoor air pollutants and virus aerosols by dry outdoor air ventilation should be assessed and compared with the beneficial health effects by control of the center zone of 40-60% RH, an essential factor for optimal functionality of the airways, and with the additional positive impact on acute symptoms, work productivity, and reduced risk of infection.

Dynamics and Viability of Airborne Respiratory Syncytial Virus under Various Indoor Air Conditions

The factors governing the viability of airborne viruses embedded within respiratory particles are not well understood. This study aimed to investigate the relative humidity (RH)-dependent viability of airborne respiratory syncytial virus (RSV) in simulated respiratory particles suspended in various indoor air conditions. We tested airborne RSV viability in three static indoor air conditions, including sub-hysteresis (RH < 39%), hysteresis (39% < RH < 65%), and super-hysteresis (RH > 65%) air as well as in three dynamic indoor air conditions, including the transitions between the static conditions. The dynamic conditions were hysteresis → super-hysteresis → hysteresis, sub-hysteresis → hysteresis, and super-hysteresis → hysteresis. We found that after 45 min of particle aging in static conditions, the viability of RSV in sub-hysteresis, hysteresis, and super-hysteresis air was 0.72% ± 0.06%, 0.03% ± 0.006%, and 0.27% ± 0.008%, respectively. After 45 min of aging in dynamic conditions, the RSV viability decreased for particles that remained in a liquid (deliquesced) state during aging when compared with particles in a solid (effloresced) state. The decreased viability of airborne RSV for deliquesced particles is consistent with prolonged exposure to elevated aqueous solutes. These results represent the first measurements of the survival of airborne RSV over particle aging time, with equal viability in low, intermediate, and high RHs at 5 and 15 min and a V-shaped curve after 45 min.

SARS-CoV-2 Survival on Surfaces. Measurements Optimisation for an Enthalpy-Based Assessment of the Risk

The present work, based on the results found in the literature, yields a consistent model of SARS-CoV-2 survival on surfaces as environmental conditions, such as temperature and relative humidity, change simultaneously. The Enthalpy method, which has recently been successfully proposed to investigate the viability of airborne viruses using a holistic approach, is found to allow us to take a reasoned reading of the data available on surfaces in the literature. This leads us to identify the domain of conditions of lowest SARS-CoV-2 viability, in a specific enthalpy range between 50 and 60 kJ/Kg_dry-air. This range appears well-superimposed with the results we previously obtained from analyses of coronaviruses' behaviour in aerosols, and may be helpful in dealing with the spread of infections. To steer future investigations, shortcomings and weaknesses emerging from the assessment of viral measurement usually carried out on surfaces are also discussed in detail. Once demonstrated that current laboratory procedures suffer from both high variability and poor standardisation, targeted implementations of standards and improvement of protocols for future investigations are then proposed.

A distributed lag non-linear time-series study of ambient temperature and healthcare-associated infections in Hefei, China

Little is known about the effects of temperature on healthcare-associated infections (HAIs). A distributed lag non-linear model was used to estimate the association between ambient temperature and HAIs in Hefei, China. In total, 9,592 HAIs were included. The effect of low temperature (-0.1°C, 2.5th percentile) was significant on the current day (RR = 1.108, 95%CI:1.003-1.222), and then appeared on the 4th day (RR = 1.045, 95%CI:1.007-1.084) and the 5th day (RR = 1.033, 95%CI:1.006-1.061). The cumulative lag effects of low temperature lasted from the 5th to 10th days (RR = 1.123-1.143), and a long-term cumulative lag effect was observed on the 14th day (RR = 1.157, 95%CI:1.001-1.338). The lag effect of high temperature (31.0°C, 97.5th percentile) was not statistically significant. However, the effects of temperatures on HAIs were not significant among gender or age subgroups. This study suggests that the low temperatures have acute and lag effects on HAIs in Hefei, China.

Cold exposure impairs extracellular vesicle swarm-mediated nasal antiviral immunity

BACKGROUND

The human upper respiratory tract is the first site of contact for inhaled respiratory viruses and elaborates an array of innate immune responses. Seasonal variation in respiratory viral infections and the importance of ambient temperature in modulating immune responses to infections have been well recognized; however, the underlying biological mechanisms remain understudied.

OBJECTIVE

We investigated the role of nasal epithelium-derived extracellular vesicles (EVs) in innate Toll-like receptor 3 (TLR3)-dependent antiviral immunity.

METHODS

We evaluated the secretion and composition of nasal epithelial EVs after TLR3 stimulation in human autologous cells and fresh human nasal mucosal surgical specimens. We also explored the antiviral activity and mechanisms of TLR3-stimulated EVs against respiratory viruses as well as the effect of cool ambient temperature on TLR3-dependent antiviral immunity.

RESULTS

We found that polyinosinic:polycytidylic acid, aka poly(I:C), exposure induced a swarm-like increase in the secretion of nasal epithelial EVs via the TLR3 signaling. EVs participated in TLR3-dependent antiviral immunity, protecting the host from viral infections through both EV-mediated functional delivery of miR-17 and direct virion neutralization after binding to virus ligands via surface receptors, including LDLR and ICAM-1. These potent antiviral immune defense functions mediated by TLR3-stimulated EVs were impaired by cold exposure via a decrease in total EV secretion as well as diminished microRNA packaging and antiviral binding affinity of individual EV.

CONCLUSION

TLR3-dependent nasal epithelial EVs exhibit multiple innate antiviral mechanisms to suppress respiratory viral infections. Furthermore, our study provides a direct quantitative mechanistic explanation for seasonal variation in upper respiratory tract infection prevalence.

A longitudinal study on the effects of hygro-thermal conditions and indoor air pollutants on building-related symptoms in office buildings

We conducted a longitudinal epidemiological study for over 1 year in Tokyo and Osaka, Japan, beginning June 2015, to examine the association between indoor environmental factors and building-related symptoms (BRSs) in office workers. Data were obtained from 483 subjects (225 females and 258 males) in 24 office rooms in 11 office buildings. Environmental monitoring was conducted for hygro-thermal conditions and carbon dioxide and sampling was performed for indoor air pollutants. Questionnaires were concurrently administered to collect information on participants' perceptions of their comfort and health and the conditions of the work environments. Multivariable analyses revealed that upper respiratory symptoms were significantly correlated with a decrease in both relative [odds ratio (OR): 0.77; 95% confidence intervals (CI): 0.62-0.95; p = 0.014] and absolute humidity (OR: 0.89; 95% CI: 0.81-0.97; p = 0.008). Statistically, significant evidence was found that average relative humidity of <38% (OR: 2.68; 95% CI: 1.36-5.27; p = 0.004) showed the most significant association with increased risk of upper respiratory symptoms. Air concentrations of carbon dioxide showed no significant correlation with BRSs at mean concentrations <1000 ppm in most buildings surveyed. Most indoor air pollutant concentrations were relatively low or lower than the values set by indoor air quality guidelines and the values of thresholds for sensory irritation. Air concentrations of indoor air pollutants showed no significant correlation with BRSs. Our data emphasize the importance of appropriate humidity control during low humidity in winter.

Decoding the Role of Temperature in RNA Virus Infections

RNA viruses include respiratory viruses, such as coronaviruses and influenza viruses, as well as vector-borne viruses, like dengue and West Nile virus. RNA viruses like these encounter various environments when they copy themselves and spread from cell to cell or host to host. Ex vivo differences, such as geographical location and humidity, affect their stability and transmission, while in vivo differences, such as pH and host gene expression, impact viral receptor binding, viral replication, and the host immune response against the viral infection. A critical factor affecting RNA viruses both ex vivo and in vivo, and defining the outcome of viral infections and the direction of viral evolution, is temperature. In this minireview, we discuss the impact of temperature on viral replication, stability, transmission, and adaptation, as well as the host innate immune response. Improving our understanding of how RNA viruses function, survive, and spread at different temperatures will improve our models of viral replication and transmission risk analyses.

Impact of Selected Meteorological Factors on COVID-19 Incidence in Southern Finland during 2020-2021

We modelled the impact of selected meteorological factors on the daily number of new cases of the coronavirus disease 2019 (COVID-19) at the Hospital District of Helsinki and Uusimaa in southern Finland from August 2020 until May 2021. We applied a DLNM (distributed lag non-linear model) with and without various environmental and non-environmental confounding factors. The relationship between the daily mean temperature or absolute humidity and COVID-19 morbidity shows a non-linear dependency, with increased incidence of COVID-19 at low temperatures between 0 to -10 °C or at low absolute humidity (AH) values below 6 g/m³. However, the outcomes need to be interpreted with caution, because the associations found may be valid only for the study period in 2020-2021. Longer study periods are needed to investigate whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has a seasonal pattern similar such as influenza and other viral respiratory infections. The influence of other non-environmental factors such as various mitigation measures are important to consider in future studies. Knowledge about associations between meteorological factors and COVID-19 can be useful information for policy makers and the education and health sector to predict and prepare for epidemic waves in the coming winters.

Prevalence of Common Diseases in Indigenous People in Colombia

The Indigenous tribe called the Wiwa lives retracted in the Sierra Nevada de Santa Marta, Colombia. Little is known about their health status and whether the health care system in place covers their needs. In 2017 and 2018, a permanent physician was in charge for the Wiwa. Diseases and complaints were registered, ranked, and classified with the ICD-10 coding. Datasets from the Indigenous health care provider Dusakawi, collected from local health points and health brigades travelling sporadically into the fields for short visits, were compared. Furthermore, a list of provided medication was evaluated regarding the recorded needs. The most common complaints found were respiratory, infectious and parasitic, and digestive diseases. The top ten diagnoses collected in the health points and in the health brigade datasets were similar, although with a different ranking. The available medication showed a basic coverage only, with a critical lack of treatment for many severe, chronic, and life-threatening diseases. Most of the detected diseases in the Indigenous population are avoidable by an improvement in health care access, an expansion of the provided medication, and an increase in knowledge, hygiene, and life standards.

Association among sentinel surveillance, meteorological factors, and infectious disease in Gwangju, Korea

The outbreak of new infectious diseases is threatening human survival. Transmission of such diseases is determined by several factors, with climate being a very important factor. This study was conducted to assess the correlation between the occurrence of infectious diseases and climatic factors using data from the Sentinel Surveillance System and meteorological data from Gwangju, Jeollanam-do, Republic of Korea. The climate of Gwangju from June to September is humid, with this city having the highest average temperature, whereas that from December to February is cold and dry. Infection rates of Salmonella (temperature: r = 0.710**; relative humidity: r = 0.669**), E. coli (r = 0.617**; r = 0.626**), rotavirus (r =  - 0.408**; r =  - 0.618**), norovirus (r =  - 0.463**; r =  - 0.316**), influenza virus (r =  - 0.726**; r =  - 0.672**), coronavirus (r =  - 0.684**; r =  - 0.408**), and coxsackievirus (r = 0.654**; r = 0.548**) have been shown to have a high correlation with seasonal changes, specifically in these meteorological factors. Pathogens showing distinct seasonality in the occurrence of infection were observed, and there was a high correlation with the climate characteristics of Gwangju. In particular, viral diseases show strong seasonality, and further research on this matter is needed. Due to the current COVID-19 pandemic, quarantine and prevention have become important to block the spread of infectious diseases. For this purpose, studies that predict infectivity through various types of data related to infection are important.

Prospective cohort study of bedroom heating and risk of common cold in children

BACKGROUND

In countries with mild winter climates and inadequate heating, the relationship between housing conditions and health outcomes in winter have not been well studied. The purpose of the present study was to evaluate the relationship between heater type and temperature factors in the bedroom and incidence of the common cold among children in Japan.

METHODS

In this prospective cohort study, we distributed baseline questionnaires and temperature loggers in December 2019 and administered follow-up questionnaires in March 2020. We recruited children under the age of 15 years. We performed Poisson regression analysis and logistic regression analysis.

RESULTS

Of 297 participants, air conditioners were the most prevalent (n = 105, 35%), followed by gas or kerosene heaters (n = 50, 17%), and floor heaters (n = 31, 10%). Air-conditioners were associated with higher incidence of all events related to the common cold, especially having a fever (adjusted incidence rate ratio (aIRR) = 1.84, 95% confidence interval (CI): 1.41-2.40). Gas or kerosene and floor heaters showed a lower incidence rate of some events related to the common cold, such as school or nursery school absence (aIRR = 0.55, 95% CI: 0.37-0.82 and aIRR = 0.39, 95% CI: 0.23-0.67, respectively). Bedroom temperature did not show a positive association, but children who always felt cold showed a higher incidence of some events related to the common cold.

CONCLUSIONS

Our findings imply that the heating approach and modal thermal comfort, such as location of heating appliances, humidity, airflow, and radiant heat, may be more important for the onset of common cold in children than bedroom temperature itself.

Relative Humidity Affects Acute Otitis Media Visits of Preschool Children to the Emergency Department

OBJECTIVE

The associations between climate variables and diseases such as respiratory infections, influenza, pediatric seizure, and gastroenteritis have been long appreciated. Infection is the main reason for acute otitis media (AOM) incidence. However, few previous studies explored the correlation between climatic parameters and AOM infections. The most important meteorological factors, temperature, relative humidity, and fine particulate matter (PM2.5), were included in this study. We studied the relationship between these meteorological factors and the AOM visits.

MATERIALS AND METHODS

It was a retrospective cross-sectional study. A linear correlation and a linear regression model were used to explore the AOM visits and meteorological factors.

RESULTS

A total of 7075 emergency department visits for AOM were identified. Relative humidity was found an independent risk factor for the AOM visits in preschool children (regression coefficient = -10.841<0, P = .039 < .05), but not in infants and school-age children. Average temperature and PM2.5 were not correlated with AOM visits.

CONCLUSION

Humidity may have a significant inverse impact on the incidence of AOM in preschool-age children.

Indoor Environmental Factors and Acute Respiratory Illness in a Prospective Cohort of Community-Dwelling Older Adults

BACKGROUND

Ambient environmental factors have been associated with respiratory infections in ecological studies, but few studies have explored the impact of indoor environmental factors in detail. The current study aimed to investigate the impact of indoor environment on the risk of acute respiratory illness (ARI) in a subtropical city.

METHOD

A prospective cohort study was conducted in 285 community-dwelling older adults from December 2016 through May 2019. Individual household indoor environment data and ARI incidence were continuously collected. A time-stratified case-crossover analysis was conducted to estimate the excess risk of ARI associated with per-unit increase of daily mean indoor temperature, relative humidity, and absolute humidity (AH).

RESULT

In total, 168 episodes of ARI were reported with an average risk of 36.8% per year. We observed a negative association of ARI with indoor AH up to 5 lag days in cool seasons, with a 6-day cumulative excess risk estimate of -9.0% (95% confidence interval, -15.9% to -1.5%). Negative associations between household temperature or relative humidity and ARI were less consistent across warm and cool seasons.

CONCLUSIONS

Lower indoor AH in household was associated with a higher risk of ARI in the community-dwelling older adults in Hong Kong during cold seasons.

Weather Conditions and COVID-19 Incidence in a Cold Climate: A Time-Series Study in Finland

Background: The current coronavirus disease 2019 (COVID-19) is spreading globally at an accelerated rate. There is some previous evidence that weather may influence the incidence of COVID-19 infection. We assessed the role of meteorological factors including temperature (T) and relative humidity (RH) considering the concentrations of two air pollutants, inhalable coarse particles (PM₁₀) and nitrogen dioxide (NO₂) in the incidence of COVID-19 infections in Finland, located in arctic-subarctic climatic zone.

Methods: We retrieved daily counts of COVID-19 in Finland from Jan 1 to May 31, 2020, nationwide and separately for all 21 hospital districts across the country. The meteorological and air quality data were from the monitoring stations nearest to the central district hospital. A quasi-Poisson generalized additional model (GAM) was fitted to estimate the associations between district-specific meteorological factors and the daily counts of COVID-19 during the study period. Sensitivity analyses were conducted to test the robustness of the results.

Results: The incidence rate of COVID-19 gradually increased until a peak around April 6 and then decreased. There were no associations between daily temperature and incidence rate of COVID-19. Daily average RH was negatively associated with daily incidence rate of COVID-19 in two hospital districts located inland. No such association was found nationwide.

Conclusions: Weather conditions, such as air temperature and relative humidity, were not related to the COVID-19 incidence during the first wave in the arctic and subarctic winter and spring. The inference is based on a relatively small number of cases and a restricted time period.

Jennings C, Parekh SH. Effect of ambient temperature on respiratory tract cells exposed to SARS-CoV-2 viral mimicking nanospheres-An experimental study

The novel coronavirus caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has reached more than 160 countries and has been declared a pandemic. SARS-CoV-2 infects host cells by binding to the angiotensin-converting enzyme 2 (ACE-2) surface receptor via the spike (S) receptor-binding protein (RBD) on the virus envelope. Global data on a similar infectious disease spread by SARS-CoV-1 in 2002 indicated improved stability of the virus at lower temperatures facilitating its high transmission in the community during colder months (December-February). Seasonal viral transmissions are strongly modulated by temperatures, which can impact viral trafficking into host cells; however, an experimental study of temperature-dependent activity of SARS-CoV-2 is still lacking. We mimicked SARS-CoV-2 with polymer beads coated with the SARS-CoV-2 S protein to study the effect of seasonal temperatures on the binding of virus-mimicking nanospheres to lung epithelia. The presence of the S protein RBD on nanosphere surfaces led to binding by Calu-3 airway epithelial cells via the ACE-2 receptor. Calu-3 and control fibroblast cells with S-RBD-coated nanospheres were incubated at 33 and 37 °C to mimic temperature fluctuations in the host respiratory tract, and we found no temperature dependence in contrast to nonspecific binding of bovine serum ablumin-coated nanospheres. Moreover, the ambient temperature changes from 4 to 40 °C had no effect on S-RBD-ACE-2 ligand-receptor binding and minimal effect on the S-RBD protein structure (up to 40 °C), though protein denaturing occurred at 51 °C. Our results suggest that ambient temperatures from 4 to 40 °C have little effect on the SARS-CoV-2-ACE-2 interaction in agreement with the infection data currently reported.

Fever-range hyperthermia promotes cGAS-STING pathway and synergizes DMXAA-induced antiviral immunity

Background: Fever-range hyperthermia or fever-range temperature (hereafter FRT) improves survival and shortens disease duration in microbial infections. However, the mechanisms of these beneficial effects still remain elusive. We hypothesized that FRT might enhance cell responsiveness to infections by promoting cGAS-STING signaling to cause enhanced production of IFN-β. Objective: To investigate the effect fever-range hyperthermia on cGAS-STING pathway. Methods: RAW 264.7 and cGAS^-/- RAW 264.7 cells, stimulated with 5μg/ml herring testis DNA (htDNA), were heated to 39.5°C and analyzed for the expression of cGAS, STING, IFN-β, and the synthesis of cGAMP and IRF3 phosphorylation. In vivo, wild type C57BL/6J mice were subjected to whole body hyperthermia (WBH) at 39.5°C. The mice were then challenged with influenza virus and analyzed for antiviral response in term of IFN-β expression, body weight and survival. Results: We found that 39.5°C FRT upregulated the expression of cGAS and STING, and induced the synthesis of cGAMP and production of IFN-β in htDNA-transfected RAW 264.7 cells more potently as compared to 37°C. Moreover, FRT+DMXAA-treated cells were better protected from vesicular stomatitis virus (VSV)-induced cytotoxicity in vitro in contrast to the nonprotected control (no FRT and DMXAA) or DMXAA treatment alone. In vivo, FRT at 39.5°C, co-administered with DMXAA, significantly induced the expression of IFN-β, showed reduced weight loss mice and exhibited 25% more survival over the course of 14 days as compared to DMXAA treated mice 37°C. Conclusion: We conclude that fever-range hyperthermia promotes cGAS-STING pathway to cause increased expression of IFN-β and mediate its antiviral effects.

Susceptibility of an Airborne Common Cold Virus to Relative Humidity

The viability of airborne respiratory viruses varies with ambient relative humidity (RH). Numerous contrasting reports spanning several viruses have failed to identify the mechanism underlying this dependence. We hypothesized that an "efflorescence/deliquescence divergent infectivity" (EDDI) model accurately predicts the RH-dependent survival of airborne human rhinovirus-16 (HRV-16). We measured the efflorescence and deliquescence RH (RH_E and RH_D, respectively) of aerosols nebulized from a protein-enriched saline carrier fluid simulating the human respiratory fluid and found the RH range of the aerosols' hygroscopic hysteresis zone (RH_E-D) to be 38-68%, which encompasses the preferred RH for indoor air (40-60%). The carrier fluid containing HRV-16 was nebulized into the sub-hysteresis zone (RH_<E) or super-hysteresis zone (RH_>D) air, to set the aerosols to the effloresced/solid or deliquesced/liquid state before transitioning the RH into the intermediate hysteresis zone. The surviving fractions (SFs) of the virus were then measured 15 min post nebulization. SFs were also measured for aerosols introduced directly into the RH_<E, RH_E-D, and RH_>D zones without transition. SFs for transitioned aerosols in the hysteresis zone were higher for effloresced (0.17 ± 0.02) than for deliquesced (0.005 ± 0.005) aerosols. SFs for nontransitioned aerosols in the RH_<E, RH_E-D, and RH_>D zones were 0.18 ± 0.06, 0.05 ± 0.02, and 0.20 ± 0.05, respectively, revealing a V-shaped SF/RH dependence. The EDDI model's prediction of enhanced survival in the hysteresis zone for effloresced carrier aerosols was confirmed.

Hospital Admissions for Respiratory Tract Infections in Children Aged 0-5 Years for 2017/2023

Aim: To compare hospital admissions across common respiratory tract infections (RTI) in 2017-21, and project possible hospital admissions for the RTIs among children aged 0-12 months and 1-5 years in 2022 and 2023. Methods: In 644 885 children aged 0-12 months and 1-5 years, we plotted the observed monthly number of RTI admissions [upper- and lower RTI, influenza, respiratory syncytial virus (RSV), and COVID-19] from January 1st, 2017 until October 31st, 2021. We also plotted the number of RTI admissions with a need for respiratory support. We used the observed data to project four different scenarios of RTI admissions for the rest of 2021 until 2023, with different impacts on hospital wards: (1) "Business as usual," (2) "Continuous lockdown," (3) "Children's immunity debt," and (4) "Maternal and child immunity debt." Results: By October 31st, 2021, the number of simultaneous RTI admissions had exceeded the numbers usually observed at the typical season peak in January, i.e., ~900. Based on our observed data and assuming that children and their mothers (who transfer antibodies to the very youngest) have not been exposed to RTI over the last one and a half years, our scenarios suggest that hospitals should be prepared to handle two to three times as many RTI admissions, and two to three times as many RTI admissions requiring respiratory support among 0-5-year-olds as normal, from November 2021 to April 2022. Conclusion: Scenarios with immunity debt suggest that pediatric hospital wards and policy makers should plan for extended capacity.

Predicting SARS-CoV-2 Weather-Induced Seasonal Virulence from Atmospheric Air Enthalpy

Following the coronavirus disease 2019 (COVID-19) pandemic, several studies have examined the possibility of correlating the virulence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, to the climatic conditions of the involved sites; however, inconclusive results have been generally obtained. Although neither air temperature nor humidity can be independently correlated with virus viability, a strong relationship between SARS-CoV-2 virulence and the specific enthalpy of moist air appears to exist, as confirmed by extensive data analysis. Given this framework, the present study involves a detailed investigation based on the first 20-30 days of the epidemic before public health interventions in 30 selected Italian provinces with rather different climates, here assumed as being representative of what happened in the country from North to South, of the relationship between COVID-19 distributions and the climatic conditions recorded at each site before the pandemic outbreak. Accordingly, a correlating equation between the incidence rate at the early stage of the epidemic and the foregoing average specific enthalpy of atmospheric air was developed, and an enthalpy-based seasonal virulence risk scale was proposed to predict the potential danger of COVID-19 outbreak due to the persistence of weather conditions favorable to SARS-CoV-2 viability. As an early detection tool, an unambiguous risk chart expressed in terms of coupled temperatures and relative humidity (RH) values was provided, showing that safer conditions occur in the case of higher RHs at the highest temperatures, and of lower RHs at the lowest temperatures. Despite the complex determinism and dynamics of the pandemic and the related caveats, the restriction of the study to its early stage allowed the proposed risk scale to result in agreement with the available infectivity data highlighted in the literature for a number of cities around the world.

Impact of climate and ambient air pollution on the epidemic growth during COVID-19 outbreak in Japan

Coronavirus disease 2019 (COVID-19) rapidly spread worldwide in the first quarter of 2020 and resulted in a global crisis. Investigation of the potential association of the spread of the COVID-19 infection with climate or ambient air pollution could lead to the development of preventive strategies for disease control. To examine this association, we conducted a longitudinal cohort study of 28 geographical areas of Japan with documented outbreaks of COVID-19. We analyzed data obtained from March 13 to April 6, 2020, before the Japanese government declared a state of emergency. The results revealed that the epidemic growth of COVID-19 was significantly associated with increase in daily temperature or sunshine hours. This suggests that an increase in person-to-person contact due to increased outing activities on a warm and/or sunny day might promote the transmission of COVID-19. Our results also suggested that short-term exposure to suspended particles might influence respiratory infections caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Further research by well-designed or well-controlled study models is required to ascertain this effect. Our findings suggest that weather has an indirect role in the transmission of COVID-19 and that daily adequate preventive behavior decreases the transmission.

Exposure to low temperatures suppresses the production of B-cell activating factor via TLR3 in BEAS-2B cells

Acute viral respiratory tract infections (RTIs) are commonly associated with cold weather; however, the mechanism behind this is still unclear. Secretory IgA (sIgA) mainly contributes to the immune response against pathogenic microorganisms in the respiratory tract. Certain pathogen-associated molecular patterns (PAMPs) induce the expression of B-cell activating factor (BAFF) in epithelial cells, macrophages, and dendritic cells. BAFF transforms B cells into plasma cells, which leads to the mass production of immunoglobulins, including IgA, on the mucosal epithelium. However, no studies have described the relationship between cold exposure and BAFF and/or sIgA in RTI. The aim of our study was to determine this relationship in vitro by investigating the effect of low temperature on BAFF production by BEAS-2B cells after the addition of toll-like receptor (TLR) ligands. We showed stimulation of polyinosinic:polycytidylic acid (poly I:C), which led BEAS-2B to produce interferon (IFN)-β. IFN-β itself induced BEAS-2B cells to produce BAFF. Janus kinase inhibitor I decreased the amount of BAFF produced in BEAS-2B cells upon stimulation with IFN-β and poly I:C. Significantly less BAFF was produced post-poly I:C stimulation in low-temperature conditions than in normal-temperature conditions (mean ± SD: 41.2 ± 23.3 [33 °C] vs. 138.3 ± 7.1 pg/mL [37 °C], P = 0.05). However, the low-temperature condition itself was not cytotoxic. The stimulation of poly I:C produced BAFF from BEAS2B cells via IFN-β production and the JAK/signal transducer and activator of transcription pathway played an important role in BAFF production in BEAS-2B cells. Cold exposure reduced BAFF production by BEAS2B cells after stimulation with the TLR3 ligand. Cold exposure may, therefore, suppress the production of BAFF, resulting in the inhibition of IgA secretion in the bronchial epithelium, which explains the increased frequency of RTIs in cold weather.

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Relationship between cold exposure and B-cell activating factor (BAFF) was assessed.

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BAFF produced post poly I:C stimulation was lesser under low-temperature conditions.

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Cold exposure may suppress BAFF production to inhibit IgA secretion.

On the Optimal Indoor Air Conditions for SARS-CoV-2 Inactivation. An Enthalpy-Based Approach

In the CoViD-19 pandemic, the precautionary approach suggests that all possible measures should be established and implemented to avoid contagion, including through aerosols. For indoor spaces, the virulence of SARS-CoV-2 could be mitigated not only via air changes, but also by heating, ventilation, and air conditioning (HVAC) systems maintaining thermodynamic conditions possibly adverse to the virus. However, data available in literature on virus survival were never treated aiming to this. In fact, based on comparisons in terms of specific enthalpy, a domain of indoor comfort conditions between 50 and 60 kJ/kg is found to comply with this objective, and an easy-to-use relationship for setting viable pairs of humidity and temperature using a proper HVAC plant is proposed. If confirmed via further investigations on this research path, these findings could open interesting scenarios on the use of indoor spaces during the pandemic.

Biological fluid dynamics of airborne COVID-19 infection

ABSTRACT

We review the state of knowledge on the bio-fluid dynamic mechanisms involved in the transmission of the infection from SARS-CoV-2. The relevance of the subject stems from the key role of airborne virus transmission by viral particles released by an infected person via coughing, sneezing, speaking or simply breathing. Speech droplets generated by asymptomatic disease carriers are also considered for their viral load and potential for infection. Proper understanding of the mechanics of the complex processes whereby the two-phase flow emitted by an infected individual disperses into the environment would allow us to infer from first principles the practical rules to be imposed on social distancing and on the use of facial and eye protection, which to date have been adopted on a rather empirical basis. These measures need compelling scientific validation. A deeper understanding of the relevant biological fluid dynamics would also allow us to evaluate the contrasting effects of natural or forced ventilation of environments on the transmission of contagion: the risk decreases as the viral load is diluted by mixing effects but contagion is potentially allowed to reach larger distances from the infected source. To that end, our survey supports the view that a formal assessment of a number of open problems is needed. They are outlined in the discussion.

GRAPHIC ABSTRACT

A predictive model of the temperature-dependent inactivation of coronaviruses

The COVID-19 pandemic has stressed healthcare systems and supply lines, forcing medical doctors to risk infection by decontaminating and reusing single-use personal protective equipment. The uncertain future of the pandemic is compounded by limited data on the ability of the responsible virus, SARS-CoV-2, to survive across various climates, preventing epidemiologists from accurately modeling its spread. However, a detailed thermodynamic analysis of experimental data on the inactivation of SARS-CoV-2 and related coronaviruses can enable a fundamental understanding of their thermal degradation that will help model the COVID-19 pandemic and mitigate future outbreaks. This work introduces a thermodynamic model that synthesizes existing data into an analytical framework built on first principles, including the rate law for a first-order reaction and the Arrhenius equation, to accurately predict the temperature-dependent inactivation of coronaviruses. The model provides much-needed thermal decontamination guidelines for personal protective equipment, including masks. For example, at 70 °C, a 3-log (99.9%) reduction in virus concentration can be achieved, on average, in 3 min (under the same conditions, a more conservative decontamination time of 39 min represents the upper limit of a 95% interval) and can be performed in most home ovens without reducing the efficacy of typical N95 masks as shown in recent experimental reports. This model will also allow for epidemiologists to incorporate the lifetime of SARS-CoV-2 as a continuous function of environmental temperature into models forecasting the spread of the pandemic across different climates and seasons.

Bayesian regression with spatiotemporal varying coefficients

To study the impact of climate variables on morbidity of some diseases in Mexico, we propose a spatiotemporal varying coefficients regression model. For that we introduce a new spatiotemporal-dependent process prior, in a Bayesian context, with identically distributed normal marginal distributions and joint multivariate normal distribution. We study its properties and characterise the dependence induced. Our results show that the effect of climate variables, on the incidence of specific diseases, is not constant across space and time and our proposed model is able to capture and quantify those changes.

Environmental and Health Effects of Ventilation in Subway Stations: A Literature Review

Environmental health in subway stations, a typical type of urban underground space, is becoming increasingly important. Ventilation is the principal measure for optimizing the complex physical environment in a subway station. This paper narratively reviews the environmental and health effects of subway ventilation and discusses the relevant engineering, environmental, and medical aspects in combination. Ventilation exerts a notable dual effect on environmental health in a subway station. On the one hand, ventilation controls temperature, humidity, and indoor air quality to ensure human comfort and health. On the other hand, ventilation also carries the potential risks of spreading air pollutants or fire smoke through the complex wind environment as well as produces continuous noise. Assessment and management of health risks associated with subway ventilation is essential to attain a healthy subway environment. This, however, requires exposure, threshold data, and thereby necessitates more research into long-term effects, and toxicity as well as epidemiological studies. Additionally, more research is needed to further examine the design and maintenance of ventilation systems. An understanding of the pathogenic mechanisms and aerodynamic characteristics of various pollutants can help formulate ventilation strategies to reduce pollutant concentrations. Moreover, current comprehensive underground space development affords a possibility for creating flexible spaces that optimize ventilation efficiency, acoustic comfort, and space perception.

Seasonality of influenza and its association with meteorological parameters in two cities of Pakistan: A time series analysis

Background

Influenza is known to have a specific pattern of seasonality the reasons for which are yet to be fully ascertained. Temperate zones show influenza epidemic during the winter months. The tropical and subtropical regions show more diverse influenza outbreak patterns. This study explores the seasonality of influenza activity and predicts influenza peak based on historical surveillance time series data in Islamabad and Multan, Pakistan.

Methods

This is a descriptive study of routinely collected monthly influenza sentinel surveillance data and meteorological data from 2012–16 in two sentinel sites of Pakistan: Islamabad (North) and Multan (Central).

Results

Mean number of cases of influenza and levels of precipitation were higher in Islamabad compared to Multan. Mean temperature and humidity levels were similar in both the cities. The number of influenza cases rose with decrease in precipitation and temperature in Islamabad during 2012–16, although the same cannot be said about humidity. The relationship between meteorological parameters and influenza incidence was not pronounced in case of Multan. The forecasted values in both the cities showed a significant peak during the month of January.

Conclusion

The influenza surveillance system gave a better understanding of the disease trend and could accurately forecast influenza activity in Pakistan.

Impacts of tropical cyclones and accompanying precipitation and wind velocity on childhood hand, foot and mouth disease in Guangdong Province, China

OBJECTIVE

Guangdong province is one of the provinces most frequently hit by tropical cyclones in China. Hand, foot and mouth disease (HFMD) continues to severely affect public health across the world. Our study aimed to evaluate the impacts of different grades of tropical cyclones and accompanying precipitation and wind velocity on HFMD among children younger than 6 years old in Guangdong province from 2009 to 2013.

METHODS

A time-stratified case-crossover design was used to examine the association between tropical cyclones and childhood HFMD. Principal component analysis (PCA) was first used to eliminate multicollinearity among meteorological variables. Conditional Poisson regression was then applied to calculate odds ratios (ORs) and the 95% confidence intervals (CIs).

RESULTS

Tropical storms increased the risk of HFMD among children below 6 years of age on lag 4 days (OR = 1.55, 95%CI: 1.28-1.88). Tropical storms were also a risk factor for boys below 3 years of age, boys between 3 and 6 and girls below 3 years of age with the largest OR = 1.52 (95%CI:1.15-2.00), OR = 1.81 (95%CI = 1.21-2.71) and OR = 1.51 (95%CI = 1.04-2.19), respectively. Precipitation during tropical cyclones had an adverse effect on childhood HFMD when reaching 25-49.9 mm or above 100 mm with OR = 1.20 (95%CI = 1.00-1.43) on lag 0 day and OR = 1.25 (95%CI = 1.04-1.49) on lag 7 days, respectively. For extreme wind velocity during tropical cyclones, the impact on childhood HFMD was largest on the day tropical cyclones landed (OR = 1.25, 95%CI: 1.06-1.48) with winds up to 13.9-24.4  m/s.

CONCLUSIONS

Tropical storms can increase the risk of HFMD among children younger than 3 years old, especially boys between 3 and 6 years old. Precipitation during tropical cyclones is a risk factor for childhood HFMD when it is between 25 and 49.9 mm or above 100 mm. As extreme wind velocity reaches 13.9-24.4  m/s, it has an adverse effect on children's health. Children below 3 years old and boys between 3 and 6 should be given more consideration during tropical storms.

Human infectious diseases and the changing climate in the Arctic

Climatic factors, especially temperature, precipitation, and humidity play an important role in disease transmission. As the Arctic changes at an unprecedented rate due to climate change, understanding how climatic factors and climate change affect infectious disease rates is important for minimizing human and economic costs. The purpose of this systematic review was to compile recent studies in the field and compare the results to a previously published review. English language searches were conducted in PubMed, ScienceDirect, Scopus, and PLOS One. Russian language searches were conducted in the Scientific Electronic Library "eLibrary.ru". This systematic review yielded 22 articles (51%) published in English and 21 articles (49%) published in Russian since 2012. Articles about zoonotic and vector-borne diseases accounted for 67% (n = 29) of the review. Tick-borne diseases, tularemia, anthrax, and vibriosis were the most researched diseases likely to be impacted by climatic factors in the Arctic. Increased temperature and precipitation are predicted to have the greatest impact on infectious diseases in the Arctic.

Climatic factors and long-term trends of influenza-like illness rates in The Netherlands, 1970-2016

BACKGROUND

Climatic factors affect the survival and transmissibility of respiratory viruses causing influenza-like illness (ILI), and we hypothesized that changes in absolute humidity and temperature may affect long-term trends of ILI incidence rate in temperate countries. We tested this hypothesis using ILI and meteorological time series in the Netherlands for the period 1970-2016.

METHODS

We described the long-term trends of ILI incidence, absolute humidity and temperature; modelled the association between climatic factors and ILI activity using negative binomial regression models; and assessed the strength of the association between the seasonal average absolute humidity (or temperature) and ILI incidence rate using the Spearman's rank correlation coefficient.

RESULTS

The ILI incidence rate declined from 1970 and reached a minimum in the season 2002-03, but started to increase again from the season 2003-04 onwards. In the negative binominal regression models, the weekly ILI count was inversely associated (p < 0.001) with 0- and 1-week lagged absolute humidity and temperature. After three decades of rising absolute humidity and temperature (1970-2000), the early 2000s represented a trend-reversal point for the climatic time series. The seasonal average ILI incidence rate and absolute humidity (or temperature) were strongly (inversely) correlated.

CONCLUSIONS

Our findings suggest that climate change may have played a role in the long-term trends of ILI incidence rates in the Netherlands, as we were able to show that lower humidity and temperature in a given week were associated with higher ILI incidence in the next week, there was a clear time point reversal in climatic parameters and ILI rates in the 2000s, and the average annual ILI incidence was inversely related to average annual temperatures and humidity.

A time for everything and everything in its time - exploring the mechanisms underlying seasonality of COPD exacerbations

Across Europe, COPD affects 23 million people leading to annual health care costs of ~€25.1 billion. This burden is particularly severe during winter months in association with the peak incidence of exacerbation events. Seasonal variation in the health status of patients with COPD places additional and often critical pressure on already strained health care resources. COPD exacerbations are characterized by worsening day-to-day symptoms of an individual and often triggered by respiratory infections, but the process by which this occurs in a seasonal fashion is likely to be multifactorial. In this review, we discuss recent population studies that highlight the impact of seasonality in COPD and review the proposed biological mechanisms underlying this. An appraisal of the role of the host susceptibility and response, environmental triggers and the biology of respiratory pathogens is detailed. The impact of each aspect is considered, and an integrated model of the context for the whole individual and society in general is explored.

[Health Risk Factors for Housing Environment and Risk Management]

After the 1990s, many effective measures were taken to improve indoor air pollution in Japan. However, as a result of major changes in building materials, consumer products, and lifestyle, and new scientific findings on health effects associated with indoor environmental pollution, new issues have been indicated, such as chemical pollutants in indoor dusts or indoor pollutants caused by new chemicals that were substituted from chemicals that Indoor Air Quality Guideline was set. On the other hand, scientific evidence for the links between housing environment and health has accumulated substantially in recent decades. Therefore, the World Health Organization (WHO) is developing Housing and Health Guidelines to provide policymakers with recommendations on healthy housing conditions such as thermal comfort, indoor air pollution, crowding, and home injuries. In this paper, the basic principles of healthy housing, the current status of Japanese dwellings, and the recent approaches of WHO are summarized.

Lower temperatures reduce type I interferon activity and promote alphaviral arthritis

Chikungunya virus (CHIKV) belongs to a group of mosquito-borne alphaviruses associated with acute and chronic arthropathy, with peripheral and limb joints most commonly affected. Using a mouse model of CHIKV infection and arthritic disease, we show that CHIKV replication and the ensuing foot arthropathy were dramatically reduced when mice were housed at 30°C, rather than the conventional 22°C. The effect was not associated with a detectable fever, but was dependent on type I interferon responses. Bioinformatics analyses of RNA-Seq data after injection of poly(I:C)/jetPEI suggested the unfolded protein response and certain type I interferon responses are promoted when feet are slightly warmer. The ambient temperature thus appears able profoundly to effect anti-viral activity in the periphery, with clear consequences for alphaviral replication and the ensuing arthropathy. These observations may provide an explanation for why alphaviral arthropathies are largely restricted to joints of the limbs and the extremities.

Urban air pollution and meteorological factors affect emergency department visits of elderly patients with chronic obstructive pulmonary disease in Taiwan

Both air pollution and meteorological factors in metropolitan areas increased emergency department (ED) visits from people with chronic obstructive pulmonary disease (COPD). Few studies investigated the associations between air pollution, meteorological factors, and COPD-related health disorders in Asian countries. This study aimed to investigate the relationship between the environmental factors and COPD-associated ED visits of susceptible elderly population in the largest Taiwanese metropolitan area (Taipei area, including Taipei city and New Taipei city) between 2000 and 2013. Data of air pollutant concentrations (PM₁₀, PM_2.5, O₃, SO₂, NO₂ and CO), meteorological factors (daily temperature, relative humidity and air pressure), and daily COPD-associated ED visits were collected from Taiwan Environmental Protection Administration air monitoring stations, Central Weather Bureau stations, and the Taiwan National Health Insurance database in Taipei area. We used a case-crossover study design and conditional logistic regression models with odds ratios (ORs), and 95% confidence intervals (CIs) for evaluating the associations between the environmental factors and COPD-associated ED visits. Analyses showed that PM_2.5, O₃, and SO₂ had significantly greater lag effects (the lag was 4 days for PM_2.5, and 5 days for O₃ and SO₂) on COPD-associated ED visits of the elderly population (65-79 years old). In warmer days, a significantly greater effect on elderly COPD-associated ED visits was estimated for PM_2.5 with coexistence of O₃. Additionally, either O₃ or SO₂ combined with other air pollutants increased the risk of elderly COPD-associated ED visits in the days of high relative humidity and air pressure difference, respectively. This study showed that joint effect of urban air pollution and meteorological factors contributed to the COPD-associated ED visits of the susceptible elderly population in the largest metropolitan area in Taiwan. Government authorities should review existing air pollution policies, and strengthen health education propaganda to ensure the health of the susceptible elderly population.