The rapid spread of influenza viruses (IV) from person to person during seasonal epidemics causes acute respiratory infections that can lead to hospitalizations and life-threatening illness. Atmospheric conditions such as relative humidity (RH) can impact the viability of IV released into the air. To understand how different IV are affected by their environment, we compared the levels of stability of human-pathogenic seasonal and avian IV under a range of RH conditions and found that highly transmissible seasonal IV were less sensitive to decay under midrange RH conditions in droplets. We observed that certain RH conditions can support the persistence of infectious viruses on surfaces and in the air for extended periods of time. Together, our findings will facilitate understanding of factors affecting the persistence and spread of IV in our environment. ABSTRACT Highly transmissible influenza viruses (IV) must remain stable and infectious under a wide range of environmental conditions following release from the respiratory tract into the air. Understanding how expelled IV persist in the environment is critical to limiting the spread of these viruses. Little is known about how the stability of different IV in expelled aerosols is impacted by exposure to environmental stressors, such as relative humidity (RH). Given that not all IV are equally capable of efficient airborne transmission in people, we anticipated that not all IV would respond uniformly to ambient RH. Therefore, we have examined the stability of human-pathogenic seasonal and avian IV in suspended aerosols and stationary droplets under a range of RH conditions. H3N2 and influenza B virus (IBV) isolates are resistant to RH-dependent decay in aerosols in the presence of human airway surface liquid, but we observed strain-dependent variations in the longevities of H1N1, H3N2, and IBV in droplets. Surprisingly, low-pathogenicity avian influenza H6N1 and H9N2 viruses, which cause sporadic infections in humans but are unable to transmit person to person, demonstrated a trend toward increased sensitivity at midrange to high-range RH. Taken together, our observations suggest that the levels of vulnerability to decay at midrange RH differ with virus type and host origin. IMPORTANCE The rapid spread of influenza viruses (IV) from person to person during seasonal epidemics causes acute respiratory infections that can lead to hospitalizations and life-threatening illness. Atmospheric conditions such as relative humidity (RH) can impact the viability of IV released into the air. To understand how different IV are affected by their environment, we compared the levels of stability of human-pathogenic seasonal and avian IV under a range of RH conditions and found that highly transmissible seasonal IV were less sensitive to decay under midrange RH conditions in droplets. We observed that certain RH conditions can support the persistence of infectious viruses on surfaces and in the air for extended periods of time. Together, our findings will facilitate understanding of factors affecting the persistence and spread of IV in our environment.

<h4>Objectives</h4>To evaluate the potential for long distance airborne transmission of SARS-CoV-2 in indoor community settings and to investigate factors that might influence transmission.<h4>Design</h4>Rapid systematic review and narrative synthesis.<h4>Data sources</h4>Medline, Embase, medRxiv, Arxiv, and WHO COVID-19 Research Database for studies published from 27 July 2020 to 19 January 2022; existing relevant rapid systematic review for studies published from 1 January 2020 to 27 July 2020; and citation analysis in Web of Science and Cocites.<h4>Eligibility criteria for study selection</h4>Observational studies reporting on transmission events in indoor community (non-healthcare) settings in which long distance airborne transmission of SARS-CoV-2 was the most likely route. Studies such as those of household transmission where the main transmission route was likely to be close contact or fomite transmission were excluded.<h4>Data extraction and synthesis</h4>Data extraction was done by one reviewer and independently checked by a second reviewer. Primary outcomes were SARS-CoV-2 infections through long distance airborne transmission (>2 m) and any modifying factors. Methodological quality of included studies was rated using the quality criteria checklist, and certainty of primary outcomes was determined using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework. Narrative synthesis was themed by setting.<h4>Results</h4>22 reports relating to 18 studies were identified (methodological quality was high in three, medium in five, and low in 10); all the studies were outbreak investigations. Long distance airborne transmission was likely to have occurred for some or all transmission events in 16 studies and was unclear in two studies (GRADE: very low certainty). In the 16 studies, one or more factors plausibly increased the likelihood of long distance airborne transmission, particularly insufficient air replacement (very low certainty), directional air flow (very low certainty), and activities associated with increased emission of aerosols, such as singing or speaking loudly (very low certainty). In 13 studies, the primary cases were reported as being asymptomatic, presymptomatic, or around symptom onset at the time of transmission. Although some of the included studies were well conducted outbreak investigations, they remain at risk of bias owing to study design and do not always provide the level of detail needed to fully assess transmission routes.<h4>Conclusion</h4>This rapid systematic review found evidence suggesting that long distance airborne transmission of SARS-CoV-2 might occur in indoor settings such as restaurants, workplaces, and venues for choirs, and identified factors such as insufficient air replacement that probably contributed to transmission. These results strengthen the need for mitigation measures in indoor settings, particularly the use of adequate ventilation.<h4>Systematic review registration</h4>PROSPERO CRD42021236762.

AbstractA new personal bioaerosol sampler has been developed and verified as an efficient tool for monitoring of viable/non‐viable airborne microorganisms, including bacteria, fungi, and viruses. The operational principle of the device is based on continuous passage of an air sample through porous media submerged into a liquid layer. During motion along narrow and tortuous ways inside the porous media, the air stream is split into a large number of ultra small bubbles with the particulates are being scavenged by these bubbles and, thus, effectively trapped. The device was initially verified for monitoring of viable airborne bacteria and fungi, firstly, under controlled laboratory conditions and later in a field. It was demonstrated that bacterial recovery rates for these two groups of microorganisms were very high and the device was found to be fully feasible for such monitoring. The next step of the device investigation was performed in the laboratory on monitoring viable airborne viruses with a range of sensitivities to physical and biological stresses. As the result, the new personal sampler demonstrated a very high recovery rate even for viruses which are rather sensitive to environmental stress (Avian Influenza, SARS, Mumps, etc.). Some following field studies, undertook in a hospital and animal houses, also demonstrated an excellent performance of the new device for selective and reliable monitoring of viable airborne viruses even in environments highly contaminated by other microorganisms. This paper reviews the main development staged of the new personal bioaerosol sampler.

The oral cavity is a unique environment which can provide an ideal medium for bacterial growth. Most of the procedures performed by dentist have the potential for creating contaminated aerosols and splatter which contains bacteria, fungi, protozoa and even blood borne viruses produced during dental operative procedures and thus promoting an increased risk of cross infection. In dentistry, the ultrasonic scaler and the air polisher are considered to be the greatest producers of small particle aerosol contamination. Aerosols can remain airborne for extended periods of time and may be inhaled and was also found that the microorganisms could survive in the aerosol produced for as long as 6 days. The association of these aerosols with the respiratory infections, opthalamic and skin infections, tuberculosis and hepatitis B have been reported. Chlorhexidine is considered as the “Gold standard” of antimicrobial rinse because of broad-spectrum antibacterial activity and substantivity of 8-12 hrs. This study determined the efficacy of preprocedural rinsing with an antimicrobial mouthrinse containing chlorhexidine in reducing the level of viable bacteria contained in aerosols generated by ultrasonic scaling. The results of the present study clearly indicate that pre-procedural mouth rinse with 0.2% chlorhexidine gluconate was significantly effective in reducing the aerosol contamination during use of ultrasonic scaling in dental practice Using a pre-procedural rinse can significantly reduce the viable microbial content of dental aerosols.

Evaluation of Moloney murine sarcoma and leukemia virus complex as a model for airborne oncogenic virus biohazards: survival of airborne virus and exposure of mice. Aerosols of the Moloney murine sarcoma virus (MuSV-M) and leukemia virus (MuLV-M) complex (MuSV-M/MuLV-M) were generated from refluxing atomizers and then aged in rotating drums at 21 degrees C holding temperature with relative humidities ranging from 25 to 76%. The MuSV-M and MuLV-M aerosolized from the same tumor extract preparation survived almost equally at the four humidity levels. Both viruses remained viable in the airborne state for at least 2 hours after aerosolization. When mice were exposed to airborne MuSV-M/MuLV-M, no macroscopic lesions were observed in lungs or other tissues examined during the 2-month postexposure period. On the basis of this study, MuSV-M was determined unsuitable as a "model system" in which a simple aerosol dose response could be used for biohazard evaluation of oncogenic virus aerosols. Published in Journal of the National Cancer Institute (1976)

Inclusion bodies (PIB) of nuclear polyhedrosis viruses (NPV) remain infectious for long periods in forest soils, but their transfer from soil to foliage is not well understood. Two instances of dispersal of the NPV of Neodiprion sertifer (Fourcroy) (Hymenoptera: Diprionidae) by dust are reported. The distribution of diseased larval colonies in a young Scots pine stand indicated that dust caused by logging during winter could have started an epizootic. At another site there was a higher frequency of infected colonies near a forest road than further into the stand. The dust transmission hypothesis was tested by bioassays of road surface material and of samples of airborne dust collected on membrane filters. Both soil and air samples contained viable PIBs. Thus, virus dispersal with dust provided a likely explanation for the observed distributions of diseased larval colonies. Zusammenfassung Ausbreitung des Kernpolyedervirus von Neodiprion sertifer von der Erde auf Kiefernnadeln mit Staub Mortalität von N. sertifer Larven durch das wirtsspezifische Kernpolyedervirus ist zwischen den Massenvermehrungen der Sägewespe selten. Eine ständige Infektionskette bleibt nicht erhalten. Das einzige bekannte Reservoir von Virusinoculum zwischen den Massenvermehrungen ist der Waldboden. Die Übertragung von Virus vom Boden auf Kiefernnadeln wird als seltenes Ereignis betrachtet. Sie dürfte häufiger sein, wenn die bodenbedeckende Vegetation gestört ist. Es wird von zwei Studien berichtet, in de

range in size from aerosols that remain suspended in the air for long periods of time to larger droplets that remain airborne briefly or fall to the ground COVID-19 is mainly transmitted from person to person through inhaling air contaminated by droplets/aerosols and small airborne particles containing the virus. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing. Transmission is most likely at closer range but can also occur over longer distances, particularly indoors. The virus spreads through virus-laden fluid par COVID-19 is mainly transmitted from person to person through inhaling air contaminated by droplets/aerosols and small airborne particles containing the virus. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing. Transmission is most likely at closer range but can also occur over longer distances, particularly indoors. The virus spreads through virus-laden fluid particles, or droplets, which are created in the respiratory tract, and they are expelled by the mouth and the nose. There are three types of transmission: "droplet" and "contact", which are associated with large droplets, and "airborne", which is associated with small droplets. If the droplets are above a certain critical size, they settle faster than they evaporate, and therefore they contaminate surfaces surrounding them. Droplets that are below a certain critical size, generally thought to be <100 micrometres (μm) diameter, evaporate faster than they settle; due to that fact, they form respiratory aerosol particles that remain airborne for a long period of time over extensive distances. Infectivity can begin four to five days before the onset of symptoms. Infected people can spread the disease even if they are pre-symptomatic or asymptomatic. Most commonly, the peak viral load in upper respiratory tract samples occurs close to the time of symptom onset and declines after the first week after symptoms begin. Current evidence suggests a duration of viral shedding and the period of infectiousness of up to ten days following symptom onset for people with mild to moderate COVID-19, and up to 20 days for persons with severe COVID-19, including immunocompromised people. Infectious particles range in size from aerosols that remain suspended in the air for long periods of time to larger droplets that remain airborne briefly or fall to the ground. Additionally, COVID-19 research has redefined the traditional understanding of how respiratory viruses are transmitted. The largest droplets of respiratory fluid do not travel far, but can be inhaled or land on mucous membranes on the eyes, nose, or mouth to infect. Aerosols are highest in concentration when people are in close… This…

deposits hundreds of millions of airborne viruses and tens of millions of bacteria every day on every square meter around the planet. Small, drifting aeroplankton Aeroplankton (or aerial plankton) are tiny lifeforms that float and drift in the air, carried by wind. Most of the living things that make up aeroplankton are very small to microscopic in size, and many can be difficult to identify because of their tiny size. Scientists collect them for study in traps and sweep nets from aircraft, kites or balloons. The study of the dispersion of these particles i W…