Effect of relative humidity and air temperature on survival of hepatitis A virus on environmental surfaces.

Stainless steel disks (diameter, 1 cm) were contaminated with fecally suspended hepatitis A virus (HAV; strain HM-175) and held at low (25% +/- 5%), medium (55% +/- 5%), high (80% +/- 5%), or ultrahigh (95% +/- 5%) relative humidity (RH) at an air temperature of 5,20, or 35 degrees C. HAV survival was inversely proportional to the level of RH and temperature, and the half-lives of the virus ranged from greater than 7 days at the low RH and 5 degrees C to about 2 h at the ultrahigh RH and 35 degrees C. In parallel tests with fecally suspended Sabin poliovirus (PV) type 1 at the low and ultrahigh RH, all PV activity was lost within 4 h at the low RH whereas at the ultrahigh RH it remained detectable up to 12 h. HAV could therefore survive much better than PV on nonporous environmental surfaces. Moreover, the ability of HAV to survive better at low levels of RH is in direct contrast to the behavior of other enteroviruses. These findings should help in understanding the genesis of HAV outbreaks more clearly and in designing better measures for their control and prevention.     

Chemical disinfection of hepatitis A virus on environmental surfaces.

Hepatitis A virus disinfection was assessed on contaminated stainless-steel disks. Ten microliters of fecally suspended hepatitis A virus was deposited on the center of each disk, dried for 20 min, and then covered with 20 microliters of the test product for 1 min. Of the 20 formulations tested, only 2% glutaraldehyde, a quaternary ammonium formulation containing 23% HCl (toilet bowl cleaner), and sodium hypochlorite (greater than 5,000 ppm [greater than 5,000 micrograms/ml] of free chlorine) reduced the virus titer by greater than 99.9%; phenolics, iodine-based products, alcohols, and solutions of acetic, peracetic, citric, and phosphoric acids were unable to do so.     

The effect of temperature and relative humidity on the survival of bacteria attached to dry solid surfaces

The effect of relative humidity (r.h.) (0%, 34% and 75%) and temperature (4, 15 and 25°C) on the desiccation survival of Pseudomonas sp., Acinetobacter calcoaceticus , a coryneform, Staphylococcus sp., and Staphylococcus aureus attached to and grown on glass surfaces was studied. The survival of Gram-negative and Gram-positive species was similar. Bacterial survival was shortest at 25°C for all species studied, and in most cases longest at 4°C. The effect of r.h. on survival varied with species. The number of microcolonies and the number of cells within microcolonies for Pseudomonas sp. increased on the dry surfaces after 7 d incubation under all desiccation conditions.     

Chemical disinfection of hepatitis A virus on environmental surfaces

Hepatitis A virus disinfection was assessed on contaminated stainless-steel disks. Ten microliters of fecally suspended hepatitis A virus was deposited on the center of each disk, dried for 20 min, and then covered with 20 microliters of the test product for 1 min. Of the 20 formulations tested, only 2% glutaraldehyde, a quaternary ammonium formulation containing 23% HCl (toilet bowl cleaner), and sodium hypochlorite (greater than 5,000 ppm [greater than 5,000 micrograms/ml] of free chlorine) reduced the virus titer by greater than 99.9%; phenolics, iodine-based products, alcohols, and solutions of acetic, peracetic, citric, and phosphoric acids were unable to do so.     

Effects of temperature, relative humidity, absolute humidity, and evaporation potential on survival of airborne Gumboro vaccine virus

Survival of airborne virus influences the extent of disease transmission via air. How environmental factors affect viral survival is not fully understood. We investigated the survival of a vaccine strain of Gumboro virus which was aerosolized at three temperatures (10°C, 20°C, and 30°C) and two relative humidities (RHs) (40% and 70%). The response of viral survival to four metrics (temperature, RH, absolute humidity [AH], and evaporation potential [EP]) was examined. The results show a biphasic viral survival at 10°C and 20°C, i.e., a rapid initial inactivation in a short period (2.3 min) during and after aerosolization, followed by a slow secondary inactivation during a 20-min period after aerosolization. The initial decays of aerosolized virus at 10°C (1.68 to 3.03 ln % min(-1)) and 20°C (3.05 to 3.62 ln % min(-1)) were significantly lower than those at 30°C (5.67 to 5.96 ln % min(-1)). The secondary decays at 10°C (0.03 to 0.09 ln % min(-1)) tended to be higher than those at 20°C (-0.01 to 0.01 ln % min(-1)). The initial viral survival responded to temperature and RH and potentially to EP; the secondary viral survival responded to temperature and potentially to RH. In both phases, survival of the virus was not significantly affected by AH. These findings suggest that long-distance transmission of airborne virus is more likely to occur at 20°C than at 10°C or 30°C and that current Gumboro vaccination by wet aerosolization in poultry industry is not very effective due to the fast initial decay.     

Influenza virus transmission is dependent on relative humidity and temperature

Using the guinea pig as a model host, we show that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. Twenty experiments performed at relative humidities from 20% to 80% and 5 degrees C, 20 degrees C, or 30 degrees C indicated that both cold and dry conditions favor transmission. The relationship between transmission via aerosols and relative humidity at 20 degrees C is similar to that previously reported for the stability of influenza viruses (except at high relative humidity, 80%), implying that the effects of humidity act largely at the level of the virus particle. For infected guinea pigs housed at 5 degrees C, the duration of peak shedding was approximately 40 h longer than that of animals housed at 20 degrees C; this increased shedding likely accounts for the enhanced transmission seen at 5 degrees C. To investigate the mechanism permitting prolonged viral growth, expression levels in the upper respiratory tract of several innate immune mediators were determined. Innate responses proved to be comparable between animals housed at 5 degrees C and 20 degrees C, suggesting that cold temperature (5 degrees C) does not impair the innate immune response in this system. Although the seasonal epidemiology of influenza is well characterized, the underlying reasons for predominant wintertime spread are not clear. We provide direct, experimental evidence to support the role of weather conditions in the dynamics of influenza and thereby address a long-standing question fundamental to the understanding of influenza epidemiology and evolution.     

建筑三维空间形态对地气能量动态、空气温度和相对湿度的影响

建筑对城市能量分配和微气候起着重要作用,探讨建筑三维空间形态与地气能量/微气候关系对气候适应性城市建设具有重大意义。基于ENVI-met的多情景模拟结果和增强回归树量化了建筑三维分形维数和三维形状指数对地气能量指标(净辐射、土壤热通量、建筑储热、感热通量和潜热通量)、空气温度和空气相对湿度的影响。研究结果表明,建筑三维分形维数、三维形状指数与地气能量动态、空气温度和空气相对湿度存在非线性关系。白天,当三维分形维数高于2.4,或三维形状指数低于2.0时,随着三维分形维数或三维形状指数的增加,三维分形维数和三维形状指数与净辐射、土壤热通量、建筑储热、感热通量、潜热通量和空气温度呈现统计负相关。夜间,当三维分形维数高于2.4,三维分形维数与感热通量和空气温度呈现负相关;与土壤热通量和潜热通量呈现正相关。夜间,当三维形状指数小于2.0时,三维形状指数与空气温度、空气相对湿度呈现负相关。当三维形状指数在2.0—2.5时,三维形状指数与感热通量、潜热通量呈现负相关;当三维形状指数高于2.5时,三维形状指数与感热通量、潜热通量不存在统计关系。白天,建筑三维分形维数的增加,净辐射、土壤热通量、建筑储热...     

Influence of temperature and relative humidity on the survival of Chlamydia pneumoniae in aerosols.

The survival of Chlamydia pneumoniae in aerosols was investigated by using a chamber with a capacity of 114.5 liters. We injected 5 x 10(7) inclusion-forming units (IFU) of C. pneumoniae in aerosols with a droplet size of 3 to 5 microns. Samples were taken after 30 s and every 1 min thereafter. The survival of C. pneumoniae was measured at four temperatures (8.5, 15, 25, and 35 degrees C) and at three different relative humidities (RH) of 5, 50, and 95% for each temperature. The survival rates of Streptococcus pneumoniae, Streptococcus faecalis, Klebsiella pneumoniae, Chlamydia trachomatis LGV2, and cytomegalovirus were also determined at 25 degrees C and 95% RH and compared with that of C. pneumoniae. At the mentioned temperatures and RH, a rapid decrease of C. pneumoniae IFU was observed in the first 30 s. After this the decrease in the number of IFU was more gradual. The survival of C. pneumoniae in aerosols were optimal at 15 to 25 degrees C and 95% RH; it was good compared with those of other microorganisms. A lower death rate was observed only in S. faecalis. In C. trachomatis, the death rate during the first 30 s was higher than that in C. pneumoniae (85 and 53.3%, respectively). After the first 30 s, the death rates in the two organisms were identical. It was concluded that transmission of C. pneumoniae via aerosols was possible. There is probably a direct transmission from person to person, taking into account the relatively short survival period of C. pneumoniae in aerosols.     

Effect of relative humidity on the airborne survival of rotavirus SA11.

Rotavirus SA11, suspended in tryptose phosphate broth with 2.5 mg of rhodamine B per ml, was aerosolized (Collison nebulizer) into a rotating drum, and the aerosols were held at 20 +/- 1 degree C with the desired relative humidity (RH). An all-glass impinger with tryptose phosphate broth was used to collect 1-min (5.6-liter) samples of air from the drum. The virus was found to survive best at medium (50 +/- 5%) RH, where its half-life was nearly 40 h. The half-life of the virus at the low (25 +/- 5%) RH level was about 9 h. Even at 72 h of aerosol age, 45 and 21% of the infectious virus remained detectable in the air at the medium and low RH levels, respectively. The high (80 +/- 5%) RH level was found to be the least favorable to the survival of the virus, since 50% of the infectious virus became undetectable within 2 h of aerosolization. In a separate experiment at the midrange RH, 3% of the infectious virus was detectable in the drum air after 223 h (9 days) of aerosol age. Rotaviruses could, therefore, survive in air for prolonged periods, thus making air a possible vehicle for their dissemination.     

Effect of relative humidity and temperature on the survival of Clausenia josefi (Hymenoptera: Encyrtidae)

The survival of adults of Clausenia josefi was investigated as a function of temperature and relative humidity. Natural severe climatic conditions were simulated and the adaptability of the parasites to such conditions was determined.

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Résumé Clausenia josefi, parasite interne de Planococcus vitis, cochenille qui attaque la vigne, a été trouvé dans la zone aride du sud d'Israël (Negev). La moyenne de la température maximum en été (Juillet-Août) est dans cette région de 34° et l'humidité relative moyenne à 14h00 est de 40%. Le début de l'été (Mai-Juin) est la période la plus sévère, quant à l'instabilité des conditions climatiques. L'apparition saisonnière de C. josefi est caractérisée par 2 pics, un premier en Juin et un second, plus petit, en Octobre-Novembre. L'objet de cette étude était de déterminer les effets de la température et de l'humidité sur la longévité des adultes de Clausenia josefi et d'expliquer les raisons de la réduction de ses populations en été.A 28°, des humidités relatives comprises entre 20% et 80% n'ont aucun effet mesurable sur la survie des adultes de C. josefi (Fig. 1). L'effet d'une baisse d'humidité relative (20%) est plus prononcé pour des durées d'exposition de 2h et plus à de hautes températures (43°) (Fig. 3). A 43°, l'augmentation de l'humidité relative provoque un accroissement marqué de la survie (Fig. 4).Les conditions extrêmes dans les vignobles en Mai-Juin, même pendant de courtes périodes de temps, pourraient affecter les populations de ce parasite entomophage. Le fait que les populations de l'hôte sont à un maximum entre Mai et Juin, masque probablement les effets défavorables des conditions extrêmes sur l'entomophage, de sorte que le pic de ses populations apparaît à ce moment. Puisque les conditions climatiques sont moins extrêmes en Juillet et Août, la réduction des populations du parasite pendant ces mois n'est pas due aux effets climatiques mais plutôt à la réduction des populations de son hôte.

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Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan. Israel. 1972 Series, No. 2226-E.     

Effects of temperature and relative humidity on mating and survival of sterile Drosophila suzukii

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a widely distributed pest species of soft-skinned fruits. Recent studies suggest the use of sterile insect technique (SIT) as a control method for this species; however, many factors can impact effectiveness of a SIT programme, including the environmental conditions. Environmental condition is critical at the time of the release and in the days afterwards, since it may impact sterile insects’ survival and ability to mate. Thus, we verified the influence of temperature and relative humidity on mating and survival of fertile and sterile D. suzukii, when insects were food provided or deprived. Highest mating rates occurred when sterile or fertile flies provided with food were exposed to 25ºC or 81%–100% relative humidity, while temperatures of 10 and 35ºC and humidity below 60% impaired mating. Overall, mating rate among food-deprived flies was low in all temperatures and humidity levels tested, but fertile insects were more prone to mate when compared to sterile flies. Survival was negatively influenced by high temperatures, low relative humidity and food deprivation. The information present in this study is useful to be considered for release of sterile D. suzukii.     

Effect of relative humidity on the airborne survival of rhinovirus-14

Rhinovirus-14, suspended in tryptose phosphate broth supplemented with uranine (physical tracer) and an antifoam, was aerosolized by use of a Collison nebulizer. The aerosols were held in a rotating drum with the relative humidity at either the low (30 +/- 5%), medium (50 +/- 5%), or high (80 +/- 5%) level at 20 +/- 1 degrees C. An all-glass impinger was used to recover the virus from the air in the drum, with the first air sample being collected after a 15-min period of aerosol stabilization. Subsequent air samples were withdrawn at 2, 4, 8, and 14 h after stabilization of the aerosol. At the low and medium relative humidity levels, the infectivity of the airborne virus was rapidly lost and less than 0.25% could be detected in the first air sample. At the high RH level, however, the airborne virus had a half-life of 13.7 +/- 1.91 h and nearly 30% of the input infectious virus could be detected in the drum air even after 24 h of aerosolization. These findings suggest that under certain environmental conditions, notably high relative humidity, air may act as a vehicle for the spread of rhinovirus infections.     

Effect of relative humidity, atmospheric temperature, and suspending medium on the airborne survival of human rotavirus

The Wa strain of human rotavirus, grown in MA-104 cells, was suspended either in tryptose phosphate broth or feces from a case of rotaviral diarrhea. It was then aerosolized into a rotating drum using a Collison nebulizer. The drum air was sampled using an all-glass impinger containing tryptose phosphate broth as collecting fluid. At 20 +/- 1 degree C, the virus aerosolized from tryptose phosphate broth was found to survive best at 50 +/- 5% relative humidity, where its half-life was 44.2 +/- 6.3 h. At 30 +/- 5% and 80 +/- 5% relative humidity, the half-life of the virus was 24.5 +/- 3.5 and 3.8 +/- 1.0 h, respectively. At 6 +/- 1 degree C, the airborne survival of the virus at the mid and low relative humidity levels was further enhanced, but at the high relative humidity it remained very similar to that seen at 20 +/- 1 degree C. When aerosols of fecally suspended human rotavirus were held at 20 +/- 1 degree C with 50 +/- 5% relative humidity, nearly 80% of the airborne virus particles remained infectious even at the aerosol age of 24 h. These findings may help in our understanding of the epidemiology of rotaviral infections.     

Influences of the complex of environmental temperature, relative humidity and air velocity on the body temperature of restrained mice (author's transl)]

Effects of the complexes of environmental factors, such as ambient-temperature, relative humidity and air velocity, on the body temperature were investigated in restrained mice. Observations were carried out before and after 60 min-exposure to various triple combinations among environmental temperatures of 15, 25 and 35 degreesC, relative humidities of 40, 65 and 90%, and air velocities of 0.2, 1.0 and 2.0 m/sec. The analysis of variance about the differences of body temperature revealed significant effects of the environmental temperature and the air velocity levels, while no significant effects were recognized of the relative humidity. Effects of the double factors, either the environmental temperature plus the relative humidity or the environmental temperature plus the air velocity, were significant at 5 or 1% level respectively. However, effects of the double factors the relative humidity plus the air velosity, as well as the triple factors were not significant. Under the environments consisted of triple factors, the environmental temperature of 20 and 25 degreesC, the relative humidities of 40 and 70% and the air velocities of 0.1 and 0.5 m/sec, significant effects at 1% level were recognized only in the environmental temperature levels. In the relative humidty or the air velocity levels, and the double or triple factor levels, no significant effects were recognized. From the results obtained, the effective temperature (Te) was indicated by the formula, Te=t+100x-v square root 38-t, in which were given the environmental temperature in t degrees C, the absolute humidity in x kg/kg and the air velocity in v m/sec.     

Effect of air temperature and humidity on ingestive behaviour of sheep

Thirty-two Polwarth ewes, of ages up to 1 year, were observed in a climatic chamber (24 to 45° C) for eight periods of 5 h each. The observations were made through a window in the chamber wall. All animals were observed four times, then shorn and observed four times again. The animals were given weighed quantities of water and feed consisting of commercial concentrate plus Rhodes grass (Chloris gayana) hay. The water and feed remaining after 5 h of observation were weighed. The following traits were analysed: time eating hay (TEH), time eating concentrate (TEC), time drinking water (TDW), weight of hay eaten (WHE), weight of concentrate eaten (WCE), volume of ingested water (VIW), ruminating time standing up (RTS), ruminating time lying down (RTL), idling time standing up (ITS), and idling time lying down (ITL). Shearing had a significant effect for all traits except ITS. Shearing resulted in higher values for all traits except for ITS and ITL. Ingestion of hay (TEH and WHE) decreased with increased air temperature and humidity, while the ingestion of concentrate (TEC) and WHE) and water (TDW and VIW) increased. Rumination decreased with increased air temperature and humidity, and was higher in shorn than in unshorn sheep.     

北京北护城河河岸带的温湿度调节效应

以北京北护城河为例,探讨具有不同结构的河岸带对温湿度的调节效应.于2011年5-10月,根据河岸带在宽度、坡度、植物种类、植被覆盖度、距路距离和距路高度等结构指标上的差异,沿南北两岸各选取4类河岸带,并在与河岸带垂直的道路两侧分别设置相应的紧邻不同城市土地利用类型的对照区.在每月下旬的晴天或多云天,从8:00到18:00,对南北8类河岸带及其对照区的气温和相对湿度进行连续10 h的观测.t检验分析表明,与对照区相比,河岸带具有明显的温湿度调节效应,能有效地改善人体的舒适度.各类河岸带的气温极显著低于对照区,而相对湿度极显著高于对照区;河岸带的日气温和日相对湿度变化较对照区和缓,且存在季节差异,河岸带在春秋季表现出更明显的温湿度日极值调节效应.各类河岸带与其对照区在温湿指数上也存在显著差异:对照区在夏季均会使人体感到很不适,而河岸带南岸在6月和8月可有效地提高人体的舒适度,北岸在8月也可改善舒适度.同时,不同类型河岸带的温湿度调节效应也存在差异:南岸对温湿度的调节效应强于北岸,北岸气温显著高于南岸,而相对湿度显著低于南岸.差异显著性的多重比较表明,南北不同类型河岸带之间在温湿度上的差异随季节而异:5月和10月的差异较显著,但6-9月的差异不显著,这些与植被覆盖度、乔木密度、冠层结构、河岸带宽度、距路距离,以及周边土地利用方式有关.研究的结果可作为城市河岸带生态服务功能评价的一部分,并可为城市河岸带的建设、修复和管理提供依据.     

Effect of changes in relative humidity and temperature on ultrathin chitosan films

We have prepared uniform films of chitosan with thicknesses 20 nm < h < 200 nm by spincoating solutions of chitosan dissolved in dilute acetic acid onto silicon substrates while controlling the spin speed and the relative humidity inside the spincoater. After neutralizing the films, they readily absorbed water in the presence of high humidity. Heating of the films to elevated temperatures caused a large irreversible decrease in the film thickness, a small increase in the index of refraction, and a reduction in water absorption, as measured using ellipsometry. Comparisons of infrared absorption measurements of chitosan films collected before and after heating indicate an increase in the degree of acetylation with heating. Collectively, these observations are consistent with the release of bound water and a chemical change similar to acetylation at elevated temperatures.     

Synergistic effect of relative humidity and temperature on the survival of rhizobia in inoculant carrier

Six strains of Rhizobium , three temperature-tolerant (U1, C13 and A19) and three temperature-sensitive strains (U10, C10 and A4) selected on the basis of previous study were used to screen the synergestic effect of different relative humidities (r.h. 50%, 65% and 90%) and temperatures (28°, 35°, 40° and 45°C) on the survival of rhizobia in inoculant carrier. At a particular temperature all the three r.h.'s were maintained. At a storage temperature of 28° and 35°C, the r.h. had little effect on the population of any of the rhizobial strains tested, but at 40° and 45°C, marked differences were observed and it was concluded that higher r.h. in conjunction with higher temperature resulted in low viable counts. The effect was similar but less obvious with the temperature-tolerant strains. It was found that 50% r.h. at different storage temperatures extended shelf life of rhizobial strains of blackgram, cowpea and arhar crops which were tested in this study in inoculant carrier.     

Effect of relative humidity on the airborne survival of rotavirus SA11

Rotavirus SA11, suspended in tryptose phosphate broth with 2.5 mg of rhodamine B per ml, was aerosolized (Collison nebulizer) into a rotating drum, and the aerosols were held at 20 +/- 1 degree C with the desired relative humidity (RH). An all-glass impinger with tryptose phosphate broth was used to collect 1-min (5.6-liter) samples of air from the drum. The virus was found to survive best at medium (50 +/- 5%) RH, where its half-life was nearly 40 h. The half-life of the virus at the low (25 +/- 5%) RH level was about 9 h. Even at 72 h of aerosol age, 45 and 21% of the infectious virus remained detectable in the air at the medium and low RH levels, respectively. The high (80 +/- 5%) RH level was found to be the least favorable to the survival of the virus, since 50% of the infectious virus became undetectable within 2 h of aerosolization. In a separate experiment at the midrange RH, 3% of the infectious virus was detectable in the drum air after 223 h (9 days) of aerosol age. Rotaviruses could, therefore, survive in air for prolonged periods, thus making air a possible vehicle for their dissemination.