Transmission of viral respiratory infections in the home

Poor growth and pneumonia seasonality in infants in the Philippines: cohort and time series studies

Children with poor nutrition are at increased risk of pneumonia. In many tropical settings seasonal pneumonia epidemics occur during the rainy season, which is often a period of poor nutrition. We have investigated whether seasonal hunger may be a driver of seasonal pneumonia epidemics in children in the tropical setting of the Philippines. In individual level cohort analysis, infant size and growth were both associated with increased pneumonia admissions, consistent with findings from previous studies. A low weight for age z-score in early infancy was associated with an increased risk of pneumonia admission over the following 12 months (RR for infants in the lowest quartile of weight for age z-scores 1.28 [95% CI 1.08 to 1.51]). Poor growth in smaller than average infants was also associated with an increased risk of pneumonia (RR for those in the lowest quartile of growth in early infancy 1.31 [95%CI 1.02 to 1.68]). At a population level, we found that seasonal undernutrition preceded the seasonal increase in pneumonia and respiratory syncytial virus admissions by approximately 10 weeks (pairwise correlation at this lag was −0.41 [95%CI −0.53 to −0.27] for pneumonia admissions, and −0.63 [95%CI −0.72 to −0.51] for respiratory syncytial virus admissions). This lag appears biologically plausible. These results suggest that in addition to being an individual level risk factor for pneumonia, poor nutrition may act as a population level driver of seasonal pneumonia epidemics in the tropics. Further investigation of the seasonal level association, in particular the estimation of the expected lag between seasonal undernutrition and increased pneumonia incidence, is recommended.

Survival of Respiratory Viruses on Fresh Produce

In addition to enteric viruses of fecal origin, emerging zoonotic viruses such as respiratory coronaviruses and influenza viruses may potentially be transmitted via contaminated foods. The goal of this study was to determine the recovery efficiencies and the survival of two respiratory viruses, namely, adenovirus 2 (Ad2) and coronavirus 229E (CoV229E), on fresh produce in comparison to the enteric poliovirus 1 (PV1). Adenovirus was recovered with efficiencies of 56.5, 31.8, and 34.8 % from lettuce, strawberries, and raspberries, respectively. Coronavirus was recovered from lettuce with an efficiency of 19.6 % yet could not be recovered from strawberries. Poliovirus was recovered with efficiencies of 76.7 % from lettuce, but only 0.06 % from strawberries. For comparison purposes, the survival of Ad2, CoV229E, and PV1 was determined for periods up to 10 days on produce. The enteric PV1 survived better than both respiratory viruses on lettuce and strawberries, with only ≤1.03 log10 reductions after 10 days of storage at 4 °C compared to CoV229E not being recovered after 4 days on lettuce and reductions of 1.97 log10 and 2.38 log10 of Ad2 on lettuce and strawberries, respectively, after 10 days. Nevertheless, these respiratory viruses were able to survive for at least several days on produce. There is therefore the potential for transfer to the hands and subsequently to the mucosa via rubbing the eyes or nose. In addition, some respiratory coronaviruses (e.g., severe acute respiratory syndrome coronavirus) and adenoviruses are also capable of replication in the gut and there is thus some potential for acquisition through the consumption of contaminated produce.

A risk assessment approach to use of antimicrobials in the home to prevent spread of infection

Home and everyday life hygiene is a key part of the public health strategy to reduce infectious disease, but an effective code of practice is required. This short review summarizes the basic scientific principles of a risk-based approach to home hygiene where hygiene procedures are applied at critical points at appropriate times. It suggests that, although detergent-based cleaning can be used to break the chain of infection, in some cases an antimicrobial agent is required.

Susceptibility to upper respiratory tract infection and touching of the eyes or nose: a cross-sectional study of Japanese workers

OBJECTIVES

This study was a cross-sectional survey of Japanese workers regarding the relationship between touching the eyes or nose and susceptibility to URTI in workers.

METHODS

The survey respondents were 4,663 Japanese workers. Subjects were surveyed via a self-administered questionnaire regarding their susceptibility to URTI and how often they touched their eyes or nose. In addition, subjects were surveyed regarding their preventive behaviors and routine behaviors thought to be associated with URTIs. A multiple logistic regression model was used to assess the relationship between susceptibility to URTI and how often the eyes or nose are touched.

RESULTS

Responses from 3,663 individuals who answered the self-administered questionnaire were analyzed. There were 1,590 individuals (42.9%) with a "frequent incidence of URTIs", defined as URTIs more than once a year. In terms of how often the eyes or nose are touched, the odds ratios (95% CI) for a frequent incidence of URTIs among the groups responding "sometimes" and "often" were 1.41 (1.21-1.63) and 1.96 (1.59-2.42) (trend test: p<0.001) compared with the groups responding "never" and "almost never". Multivariate-adjusted odds ratios adjusted for confounding factors, i.e., behaviors to prevent URTIs, routine behaviors associated with URTIs, age, sex and BMI, were 1.33 (1.14-1.54) and 1.69 (1.36-2.09) (trend test: p<0.001).

CONCLUSIONS

The present cross-sectional study indicates that susceptibility to URTI and how often the eyes or nose are touched are significantly associated in Japanese workers, independent of preventive behaviors and routine behaviors associated with URTIs

Factors influencing hand washing behaviour in primary schools: process evaluation within a randomized controlled trial

This article explores factors that may influence hand washing behaviour among pupils and staff in primary schools. A qualitative process evaluation within a cluster randomized controlled trial included pupil focus groups (n = 16, aged 6-11 years), semi-structured interviews (n = 16 teachers) and observations of hand washing facilities (n = 57). Pupils and staff in intervention and control schools demonstrated a similar level of understanding of how, when and why they should wash their hands. Lack of time, poor adult modelling of regular hand washing and unattractive facilities were seen as important barriers to regular hand washing. Reminders and explanations for the importance of hand hygiene were thought to have a positive impact. Influencing individual choices about hand washing through education and information may be necessary, but not sufficient, for initiating and maintaining good hand washing practices. Structural factors, including having time to wash hands using accessible, clean facilities, and being encouraged through the existence of hand washing opportunities in the daily routine and hand washing being viewed as the social norm, will also influence hand washing behaviour. The effectiveness of educational interventions at improving hand hygiene in primary schools may be improved by changing priorities of staff and increasing accessibility to quality facilities.

Hand hygiene to reduce community transmission of influenza and acute respiratory tract infection: a systematic review

Hand hygiene may be associated with modest protection against some acute respiratory tract infections, but its specific role in influenza transmission in different settings is unclear. We aimed to review evidence that improving hand hygiene reduces primary and secondary transmission of (i) influenza and (ii) acute respiratory tract infections in community settings. We searched Medline, Embase, Global Health and Cochrane databases up to 13 February 2012 for reports in any language of original research investigating the effect of hand hygiene on influenza or acute respiratory tract infection where aetiology was unspecified in community settings including institutions such as schools, and domestic residences. Data were presented and quality rated across outcomes according to the Grading of Recommendations Assessment, Development and Evaluation system. Sixteen articles met inclusion criteria. There was moderate to low-quality evidence of a reduction in both influenza and respiratory tract infection with hand hygiene interventions in schools, greatest in a lower-middle-income setting. There was high-quality evidence of a small reduction in respiratory infection in childcare settings. There was high-quality evidence for a large reduction in respiratory infection with a hand hygiene intervention in squatter settlements in a low-income setting. There was moderate- to high-quality evidence of no effect on secondary transmission of influenza in households that had already experienced an index case. While hand hygiene interventions have potential to reduce transmission of influenza and acute respiratory tract infections, their effectiveness varies depending on setting, context and compliance.

Seasonality of viral respiratory infections in southeast of Brazil: the influence of temperature and air humidity

Viruses are the major cause of lower respiratory tract infections in childhood and the main viruses involved are Human Respiratory Syncytial Virus (HRSV), Human Metapneumovirus (HMPV), Influenzavirus A and B (FLUA and FLUB), Human Parainfluenza Virus 1, 2 and 3 (HPIV1, 2 and 3) and Human Rhinovirus (HRV). The purposes of this study were to detect respiratory viruses in hospitalized children younger than six years and identify the influence of temperature and relative air humidity on the detected viruses. Samples of nasopharyngeal washes were collected from hospitalized children between May/2004 and September/2005. Methods of viral detection were RT-PCR, PCR and HRV amplicons were confirmed by hybridization. Results showed 54% (148/272) of viral positivity. HRSV was detected in 29% (79/272) of the samples; HRV in 23.1% (63/272); HPIV3 in 5.1% (14/272); HMPV in 3.3% (9/272); HPIV1 in 2.9% (8/272); FLUB in 1.4% (4/272), FLUA in 1.1% (3/272), and HPIV2 in 0.3% (1/272). The highest detection rates occurred mainly in the spring 2004 and in the autumn 2005. It was observed that viral respiratory infections tend to increase as the relative air humidity decreases, showing significant association with monthly averages of minimal temperature and minimal relative air humidity. In conclusion, viral respiratory infections vary according to temperature and relative air humidity and viral respiratory infections present major incidences it coldest and driest periods.

A point-source norovirus outbreak caused by exposure to fomites

We investigated a norovirus outbreak (genotype GII.2) affecting 9 members of a soccer team. Illness was associated with touching a reusable grocery bag or consuming its packaged food contents (risk difference, 0.636; P < .01). By polymerase chain reaction, GII norovirus was recovered from the bag, which had been stored in a bathroom used before the outbreak by a person with norovirus-like illness. Airborne contamination of fomites can lead to subsequent point-source outbreaks. When feasible, we recommend dedicated bathrooms for sick persons and informing cleaning staff (professional or otherwise) about the need for adequate environmental sanitation of surfaces and fomites to prevent spread.

Cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management

BACKGROUND

The Influenza A H1N1 virus can be transmitted via direct, indirect, and airborne route to non-infected subjects when an infected patient coughs, which expels a number of different sized droplets to the surrounding environment as an aerosol. The objective of the current study was to characterize the human cough aerosol pattern with the aim of developing a standard human cough bioaerosol model for Influenza Pandemic control.

METHOD

45 healthy non-smokers participated in the open bench study by giving their best effort cough. A laser diffraction system was used to obtain accurate, time-dependent, quantitative measurements of the size and number of droplets expelled by the cough aerosol.

RESULTS

Voluntary coughs generated droplets ranging from 0.1 - 900 microns in size. Droplets of less than one-micron size represent 97% of the total number of measured droplets contained in the cough aerosol. Age, sex, weight, height and corporal mass have no statistically significant effect on the aerosol composition in terms of size and number of droplets.

CONCLUSIONS

We have developed a standard human cough aerosol model. We have quantitatively characterized the pattern, size, and number of droplets present in the most important mode of person-to-person transmission of IRD: the cough bioaerosol. Small size droplets (< 1 μm) predominated the total number of droplets expelled when coughing. The cough aerosol is the single source of direct, indirect and/or airborne transmission of respiratory infections like the Influenza A H1N1 virus.

STUDY DESIGN

Open bench, Observational, Cough, Aerosol study.

Environmental factors affecting the transmission of respiratory viruses

Many viruses are capable of infecting the human respiratory tract to cause disease. These viruses display various transmission patterns among humans; however, they all share the ability to transmit from person to person, and their human transmissibility is influenced by the environment in which pathogen and host meet. This review aims to summarize recent and significant observations regarding the impact of environmental factors such as weather and climate, humidity, temperature, and airflow on the transmission of human respiratory viruses. Where possible, knowledge gaps that require further scientific study will be identified.

A home toolkit for primary prevention of influenza by individuals and families

An influenza pandemic can overwhelm the capacities of hospitals, clinics, nursing facilities, and emergency services. The likelihood is that most of the individuals who are stricken will be cared for at home, and there is strong evidence that in-home caregivers bear a disproportionate risk of becoming infected. We reviewed the scientific literature after 2000 to identify steps that in-home caregivers can take to reduce the chances that they and other household members will become infected in the home. Personal hygiene, common masks, and technologies including air filters and UV light each offer incremental benefits, and in combination are expected to reduce a portion of the risk that household members face when caring for a member who has become infected. In pandemics and even seasonal epidemics, seemingly small steps can literally mean the difference between life and death, especially for in-home caregivers.

In China, students in crowded dormitories with a low ventilation rate have more common colds: evidence for airborne transmission

Objective

To test whether the incidence of common colds among college students in China is associated with ventilation rates and crowdedness in dormitories.

Methods

In Phase I of the study, a cross-sectional study, 3712 students living in 1569 dorm rooms in 13 buildings responded to a questionnaire about incidence and duration of common colds in the previous 12 months. In Phase II, air temperature, relative humidity and CO₂ concentration were measured for 24 hours in 238 dorm rooms in 13 buildings, during both summer and winter. Out-to indoor air flow rates at night were calculated based on measured CO₂ concentrations.

Results

In Phase I, 10% of college students reported an incidence of more than 6 common colds in the previous 12 months, and 15% reported that each infection usually lasted for more than 2 weeks. Students in 6-person dorm rooms were about 2 times as likely to have an incidence of common colds ≥6 times per year and a duration ≥2 weeks, compared to students in 3-person rooms. In Phase II, 90% of the measured dorm rooms had an out-to indoor air flow rate less than the Chinese standard of 8.3 L/s per person during the heating season. There was a dose-response relationship between out-to indoor air flow rate per person in dorm rooms and the proportion of occupants with annual common cold infections ≥6 times. A mean ventilation rate of 5 L/(s•person) in dorm buildings was associated with 5% of self reported common cold ≥6 times, compared to 35% at 1 L/(s•person).

Conclusion

Crowded dormitories with low out-to indoor airflow rates are associated with more respiratory infections among college students.

A respiratory syncytial virus isolate enables the testing of virucidal products

The respiratory syncytial virus (RSV) is known as a major cause of respiratory infections and nosocomial diseases. Testing this virus is rather difficult due to the problems encountered in producing it at a high titer without using any purification method. A RSV isolate which replicates to high level on a Hep-2 cell line with an infectious titer of at least 10(7)TCID(50)mL(-1) in culture supernatant fluids has been identified. Thanks to this isolate, the virucidal effects of two products, a hand rub solution and a surface disinfectant, were conveniently tested according to the EN 14476:2007-02 procedure.

Effect of low-concentration chlorine dioxide gas against bacteria and viruses on a glass surface in wet environments

Aims:  To evaluate the efficacy of low‐concentration chlorine dioxide (ClO₂) gas against model microbes in the wet state on a glass surface.

Methods and Results:  We set up a test room (39 m³) and the ClO₂ gas was produced by a ClO₂ gas generator that continuously releases a constant low‐concentration ClO₂ gas. Influenza A virus (Flu‐A), feline calicivirus (FCV), Staphylococcus aureus and Escherichia coli were chosen as the model microbes. The low‐concentration ClO₂ gas (mean 0·05 ppmv, 0·14 mg m⁻³) inactivated Flu‐A and E. coli (>5 log₁₀ reductions) and FCV and S. aureus (>2 log₁₀ reductions) in the wet state on glass dishes within 5 h.

Conclusions:  The treatment of wet environments in the presence of human activity such as kitchens and bathrooms with the low‐concentration ClO₂ gas would be useful for reducing the risk of infection by bacteria and viruses residing on the environmental hard surfaces without adverse effects.

Significance and Impact of the Study:  This study demonstrates that the low‐concentration ClO₂ gas (mean 0·05 ppmv) inactivates various kinds of microbes such as Gram‐positive and Gram‐negative bacteria, enveloped and nonenveloped viruses in the wet state.

Potential role of human challenge studies for investigation of influenza transmission

The importance of different routes of influenza transmission (including the role of bioaerosols) and the ability of masks and hand hygiene to prevent transmission remain poorly understood. Interest in transmission of influenza has grown as the effectiveness of prevention measures implemented during the 2009 H1N1 pandemic are questioned and as plans to better prepare for the next pandemic are debated. Recent studies of naturally infected patients have encountered difficulties and have fallen short of providing definitive answers. Human challenge studies with influenza virus date back to the 1918 pandemic. In more recent decades they have been undertaken to investigate the efficacy of antiviral agents and vaccines. Could experimental challenge studies, in which volunteers are deliberately infected with influenza virus, provide an alternative approach to the study of transmission? Here, we review the latest intervention studies and discuss the potential of challenge studies to address the remaining gaps in our knowledge.

Rainfall, household crowding, and acute respiratory infections in the tropics

SUMMARYAcute respiratory infections (ARI) are the leading cause of death worldwide in children aged <5 years, and understanding contributing factors to their seasonality is important for targeting and implementing prevention strategies. In tropical climates, ARI typically peak during the pre-rainy and rainy seasons. One hypothesis is that rainfall leads to more time spent indoors, thus increasing exposure to other people and in turn increasing the risk of ARI. A case-crossover study design in 718 Bangladeshi children aged <5 years was used to evaluate this hypothesis. During a 3-month period with variable rainfall, rainfall was associated with ARI [odds ratio (OR) 2·97, 95% confidence interval (CI) 1·87-4·70]; some evidence of an increased strength of association as household crowding increased was found (≥3 people/room, OR 3·31, 95% CI 2·03-5·38), but there was a lack of association in some of the most crowded households (≥5 to <6 people/room, OR 1·55, 95% CI 0·54-4·47). These findings suggest that rainfall may be increasing exposure to crowded conditions, thus leading to an increased risk of ARI, but that additional factors not captured by this analysis may also play a role.

Influenza vaccination in healthy working adults in Russia: observational study of effectiveness and return on investment for the employer

BACKGROUND

All age groups are affected by influenza infection, resulting in significant medical and economic burden. Influenza infection of healthy working adults can have a marked effect on companies due to lost work days and reduced productivity. Studies in corporate settings have shown that vaccination programmes reduce this burden, although there is a lack of data in Eastern European countries.

OBJECTIVES

To determine the effectiveness of influenza vaccination in healthy working adults in Russia and the economic benefits of such a programme from an employer's perspective.

METHODS

In a prospective, non-randomized, non-placebo-controlled, observational study, healthy vaccinated and unvaccinated adults employed at the Russian Railways Public Corporation were followed for 8 months during the 2005-6 influenza season using questionnaires. A first questionnaire was administered at inclusion to collect general employee information; a second questionnaire was administered to collect data on post-vaccination adverse events; and monthly questionnaires were used to gather data on influenza-like illness (ILI). Effectiveness calculations and cost analyses were performed to evaluate the impact of the influenza vaccination programme on employee productivity and costs for the employer. The study vaccine used was the trivalent, inactivated, split vaccine Vaxigrip® (sanofi pasteur, France).

RESULTS

A total of 1331 employees volunteered for the study: 701 were vaccinated and 630 were not. The vaccine effectiveness was 70.4% against ILI events and 80.8% against sick leave days. Assuming that employees working with ILI symptoms had a reduced level of productivity (30-70% of normal), cost savings per vaccinated employee ranged from &U20AC;2.13 to &U20AC;5.43.

CONCLUSIONS

This study showed that an influenza vaccination programme significantly reduced ILI episodes and absenteeism, and may provide a positive return on investment for the employer.

Analysis of residual chemicals on filtering facepiece respirators after decontamination

The N95 filtering facepiece respirator (FFR) is commonly used to protect individuals from infectious aerosols. Health care experts predict a shortage of N95 FFRs if a severe pandemic occurs, and an option that has been suggested for mitigating such an FFR shortage is to decontaminate and reuse the devices. Before the effectiveness of this strategy can be established, many parameters affecting respiratory protection must be measured: biocidal efficacy of the decontamination treatment, filtration performance, pressure drop, fit, and toxicity to the end user post treatment. This research effort measured the amount of residual chemicals created or deposited on six models of FFRs following treatment by each of 7 simple decontamination technologies. Measured amounts of decontaminants retained by the FFRs treated with chemical disinfectants were small enough that exposure to wearers will be below the permissible exposure limit (PEL). Toxic by-products were also evaluated, and two suspected toxins were detected after ethylene oxide treatment of FFR rubber straps. The results provide encouragement to efforts promoting the evolution of effective strategies for decontamination and reuse of FFRs.

Prevalence and characteristics of asymptomatic norovirus infection in the community in England

Norovirus is a major cause of infectious intestinal disease, and a substantial prevalence of asymptomatic infection has been reported. We describe the prevalence, seasonality and characteristics of asymptomatic norovirus infection in England. Healthy individuals were recruited at random from the general population during the Study of Infectious Intestinal Disease (1993-1996). Norovirus was identified using real-time RT-PCR. The age-adjusted prevalence of asymptomatic norovirus infection was 12%; prevalence was highest in children aged <5 years and showed wintertime seasonality. More work is needed to understand whether asymptomatic infections are important for norovirus transmission leading to sporadic illness and outbreaks.

Issues Concerning Survival of Viruses on Surfaces

Viruses are the causative agents of an estimated 60% of human infections worldwide. The most common viral illnesses are produced by enteric and respiratory viruses. Transmission of these viruses from an infected person or animal to a new host can occur via several routes. Existing studies strongly suggest that contaminated fomites or surfaces play an important role in the spreading of viral diseases. The potential of viral spreading via contaminated surfaces depends particularly on the ability of the virus to maintain infectivity whilst it is in the environment. This is affected by a combination of biological, physical and chemical factors. This review summarises current knowledge about the influence of environmental factors on the survival and spread of viruses via contaminated surfaces.

The Prevalence of Human Parainfluenza Virus 1 on Indoor Office Fomites

The objective of this study was to evaluate the potential role of fomites in human parainfluenza virus 1 (HPIV1) transmission by assessing the occurrence of HPIV1 on surfaces in an adult setting (office). In 2004, a total of 328 fomites from 12 different office buildings in five different cities were evaluated for HPIV1 viral RNA. HPIV1 was isolated using reverse transcriptase–polymerase chain reaction (RT–PCR) and detected on 37% of all office fomites. HPIV1 RNA was frequently isolated on desk tops (47%), and infrequently isolated on light switches (19%). Data revealed a statistically significant difference between the percentage of HPIV1 positive fomites in office cubicles and conference rooms (Chi-square P < 0.011, Fisher’s Exact P = 0.054). A statistically significant difference was also found among positive fomites in different buildings (Chi-square P < 0.011). HPIV1 was consistently isolated on various indoor fomites in the 12 office buildings assessed during 2004, a low HPIV incident year.

Nosocomial RSV infection control and outbreak management

The incidence of nosocomial respiratory syncytial virus (RSV) infection in different areas of the world is not well known. However, it is clear that RSV infection of hospitalized infants with congenital heart disease or following preterm birth is highly relevant. Nosocomial RSV infection in these high-risk group infants often follows a severe course of disease, even resulting in mortality. Transmission of RSV mainly occurs through direct contact, but not through inhalation. Consequently, prevention of nosocomial RSV infection should aim to prevent direct contact between non-infected infants and RSV-infected people. Evidence of the role of gowns, masks and gloves is discussed. The effect and safety of cohorting RSV-infected infants is reviewed. International guidelines with respect to RSV prevention and outbreak management are analysed.

Cold oxygen plasma technology efficiency against different airborne respiratory viruses

BACKGROUND

Respiratory infections caused by viruses are major causes of upper and lower respiratory tract infections. They account for an important mortality and morbidity worldwide. Amongst these viruses, influenza viruses and paramyxoviruses are major pathogens. Their transmission is mainly airborne, by direct transmission through droplets from infected cases.

OBJECTIVES

In the context of an influenza pandemic, as well as for the reduction of nosocomial infections, systems that can reduce or control virus transmission will reduce the burden of this disease. It may also be part of the strategy for pandemic mitigation.

STUDY DESIGN

A new system based on physical decontamination of surface and air has been developed. This process generates cold oxygen plasma (COP) by subjecting air to high-energy deep-UV light. To test its efficiency, we have developed an experimental device to assess for the decontamination of nebulized respiratory viruses. High titer suspensions of influenza virus type A, human parainfluenza virus type 3 and RSV have been tested.

RESULTS

Different experimental conditions have been evaluated against these viruses. The use of COP with an internal device allowed the best results against all viruses tested. We recorded a reduction of 6.5, 3.8 and 4 log(10) TCID50/mL of the titre of the hPIV-3, RSV and influenza virus A (H5N2) suspensions.

CONCLUSIONS

The COP technology is an efficient and innovative strategy to control airborne virus dissemination. It could successfully control nosocomial diffusion of respiratory viruses in hospital setting, and could be useful for the reduction of influenza transmission in the various consultation settings implemented for the management of cases during a pandemic.

An optimized method to detect influenza virus and human rhinovirus from exhaled breath and the airborne environment

Respiratory viruses are difficult to characterize in the airborne environment due to their low concentration and the presence of a wide range of inhibitors. As a first step in studying airborne viruses, we optimized molecular biology methods to quantify influenza viruses and human rhinovirus. Quantitative PCR was used as an endpoint to evaluate RNA extraction techniques and reverse transcription protocols. We found that a Trizol-chloroform extraction and MultiScribe RT increased virus detection 10-fold compared to methods used in published field studies of airborne respiratory viruses. Virus was recovered without inhibition from samples contaminated with up to 50 microg/sample of particulate matter. The methods developed can be used in studies of airborne respiratory viruses.

Exploration of the effectiveness of social distancing on respiratory pathogen transmission implicates environmental contributions

Background. In both military and civilian settings, transmission of respiratory pathogens may be due to person-to-person and environmental contributions. This possibility was explored in a military training setting, where rates of febrile respiratory illness (FRI) often reach epidemic levels.

Methods. Population size and FRI rates were monitored over 10 months in the units of 50–90 individuals. Some units were open to the influx of potentially infectious convalescents (hereafter referred to as “open units,” and some were closed to such an influx (hereafter referred to as “closed units”). Virologic testing and polymerase chain reaction analysis were used to detect adenovirus on surface structures.

Results. The odds ratio (OR) associated with FRI in closed units, compared with open units, was 1.13 (95% confidence interval [CI], 0.99–1.28). The OR in units with a population greater than the median size, compared with units with a population lower than the median size was 1.38 (95% CI, 1.23–1.55). Between 5% and 9% of surface samples obtained from selected units harbored viable adenovirus.

Conclusions. FRI rates were not reduced in units that were closed to potentially contagious individuals. These findings imply that the primary source of the pathogen is likely environmental rather than human, and they underscore what is known about other virus types. Diligence in identifying the relative roles of different transmission routes is suggested for civilian settings similar to those described in the current study.

Climatic, temporal, and geographic characteristics of respiratory syncytial virus disease in a tropical island population

Respiratory syncytial virus (RSV) is an important cause of morbidity in children worldwide, although data from equatorial regions are limited. We analysed climatic, spatial, and temporal data for children presenting to hospitals in Lombok island, Indonesia with clinical pneumonia. During the study period, 2878 children presented and 741 RSV cases were identified. In multivariate analysis with an 8-day lag, occurrence of rain was associated with 64% higher incidence of RSV disease [incidence rate ratio (IRR) 1.64, 95% confidence interval (CI) 1.13-2.38]. A 1% rise in mean relative humidity and 1 degree C increase in mean air temperature was associated with a 6% (IRR 1.06, 95% CI 1.03-1.10) and 44% (IRR 1.44, 95% CI 1.24-1.66) increase in RSV cases, respectively. Four statistically significant local clusters of RSV pneumonia were identified within the annual island-wide epidemics. This study demonstrates statistical association of monsoon-associated weather in equatorial Indonesia with RSV. Moreover, within the island-wide epidemics, localized RSV outbreaks suggest local factors influence RSV disease.

Airflow and droplet spreading around oxygen masks: a simulation model for infection control research

Background

Respiratory assist devices, such as oxygen masks, may enhance the potential to spread infectious aerosols from patients with respiratory infections.

Methods

A technique was developed to visualize exhaled aerosols during simulated patients' use of oxygen masks in a health care setting and tested using the simple, the nonrebreathing, and the Venturi oxygen masks. A smoke tracer was introduced into one of the lungs of the model to enable it to mix with the incoming oxygen and then to be further inhaled/exhaled by the model according to a variety of realistic respiratory settings (14, 24, and 30 breaths per minute, with tidal volumes of 500, 330, 235 mL, respectively) and oxygen supply flow rates (between 6 and 15 liters per minute). Digital recordings of these exhaled airflow patterns allowed approximate distances to be estimated for the extent of the visible exhaled air plumes emitted from each oxygen mask type at these settings.

Results

It was found that the simple, the nonrebreathing, and the Venturi-type oxygen masks produced exhaled smoke plumes over minimum distances of 0.08 to 0.21 m, 0.23 to 0.36 m, and 0.26 to 0.40 m, respectively.

Conclusion

Health care workers may therefore consider any area within at least 0.4 m of a patient using such oxygen masks to be a potential nosocomial hazard zone.

Role of ventilation in airborne transmission of infectious agents in the built environment - a multidisciplinary systematic review

There have been few recent studies demonstrating a definitive association between the transmission of airborne infections and the ventilation of buildings. The severe acute respiratory syndrome (SARS) epidemic in 2003 and current concerns about the risk of an avian influenza (H5N1) pandemic, have made a review of this area timely. We searched the major literature databases between 1960 and 2005, and then screened titles and abstracts, and finally selected 40 original studies based on a set of criteria. We established a review panel comprising medical and engineering experts in the fields of microbiology, medicine, epidemiology, indoor air quality, building ventilation, etc. Most panel members had experience with research into the 2003 SARS epidemic. The panel systematically assessed 40 original studies through both individual assessment and a 2-day face-to-face consensus meeting. Ten of 40 studies reviewed were considered to be conclusive with regard to the association between building ventilation and the transmission of airborne infection. There is strong and sufficient evidence to demonstrate the association between ventilation, air movements in buildings and the transmission/spread of infectious diseases such as measles, tuberculosis, chickenpox, influenza, smallpox and SARS. There is insufficient data to specify and quantify the minimum ventilation requirements in hospitals, schools, offices, homes and isolation rooms in relation to spread of infectious diseases via the airborne route. PRACTICAL IMPLICATION: The strong and sufficient evidence of the association between ventilation, the control of airflow direction in buildings, and the transmission and spread of infectious diseases supports the use of negatively pressurized isolation rooms for patients with these diseases in hospitals, in addition to the use of other engineering control methods. However, the lack of sufficient data on the specification and quantification of the minimum ventilation requirements in hospitals, schools and offices in relation to the spread of airborne infectious diseases, suggest the existence of a knowledge gap. Our study reveals a strong need for a multidisciplinary study in investigating disease outbreaks, and the impact of indoor air environments on the spread of airborne infectious diseases.

Inactivation of influenza A virus on copper versus stainless steel surfaces

Influenza A virus particles (2 x 10(6)) were inoculated onto copper or stainless steel and incubated at 22 degrees C at 50 to 60% relative humidity. Infectivity of survivors was determined by utilizing a defined monolayer with fluorescent microscopy analysis. After incubation for 24 h on stainless steel, 500,000 virus particles were still infectious. After incubation for 6 h on copper, only 500 particles were active.

Airflows around oxygen masks: A potential source of infection?

Patients with respiratory infections often require the use of supplemental oxygen via oxygen masks, which, in the hospital, may become sources of aerosolized infectious pathogens. To assess this risk, a human lung model (respiration rate, 12 breaths/min) was designed to test the potential for a simple oxygen mask at a common setting (4 L/min) to disperse potentially infectious exhaled air into the surrounding area. A laser sheet was used to illuminate the exhaled air from the mask, which contained fine tracer smoke particles. An analysis of captured digital images showed that the exhaled air at the peak of simulated exhalation reached a distance of approximately 0.40 m.

Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises

The epidemics of severe acute respiratory syndrome (SARS) in 2003 highlighted both short- and long-range transmission routes, i.e. between infected patients and healthcare workers, and between distant locations. With other infections such as tuberculosis, measles and chickenpox, the concept of aerosol transmission is so well accepted that isolation of such patients is the norm. With current concerns about a possible approaching influenza pandemic, the control of transmission via infectious air has become more important. Therefore, the aim of this review is to describe the factors involved in: (1) the generation of an infectious aerosol, (2) the transmission of infectious droplets or droplet nuclei from this aerosol, and (3) the potential for inhalation of such droplets or droplet nuclei by a susceptible host. On this basis, recommendations are made to improve the control of aerosol-transmitted infections in hospitals as well as in the design and construction of future isolation facilities.

Droplet fate in indoor environments, or can we prevent the spread of infection?

When considering how people are infected and what can be done to prevent the infections, answers from many disciplines are sought: microbiology, epidemiology, medicine, engineering, and physics. There are many pathways to infection spread, and among the most significant from the epidemiological point of view is airborne transport. Microorganisms can become airborne when droplets are generated during speech, coughing, sneezing, vomiting, or atomization of feces during sewage removal. The fate of the droplets is governed by the physical principles of transport, with droplet size being the most important factor affecting their dispersion, deposition on surfaces and determining the survival of microorganisms within the droplets. In addition, physical characteristics of the indoor environment as well as the design and operation of building ventilation systems are of critical importance. Do we understand the mechanisms of infection spread and can we quantify the droplet dynamics under various indoor conditions? Unfortunately no, as this aspect of infection spread has attracted surprisingly little scientific interest. However, investigations of numerous cases in which a large number of people were infected show how critical the physics of microorganism spread can be. This paper reviews the state of knowledge regarding mechanisms of droplet spread and solutions available to minimize the spread and prevent infections.

PRACTICAL IMPLICATIONS

Every day tens of millions of people worldwide suffer from viral infections of different severity at immense economic cost. There is, however, only minimal understanding of the dynamics of virus-laden aerosols, and so the ability to control and prevent virus spread is severely reduced, as was clearly demonstrated during the recent severe acute respiratory syndrome epidemic. This paper proposes the direction to significantly advance fundamental and applied knowledge of the pathways of viral infection spread in indoor atmospheric systems, through a comprehensive multidisciplinary approach and application of state-of-the-art scientific methods. Knowledge gained will have the potential to bring unprecedented economical gains worldwide by minimizing/reducing the spread of disease.

Potential benefits and limitations of various strategies to mitigate the impact of an influenza pandemic

The recent avian influenza outbreaks underscore the importance of improving our preparedness for an impending influenza pandemic. Various strategies, including pharmaceutical interventions (such as vaccines and antivirals) and nonpharmaceutical interventions (such as quarantine, isolation, and social distancing) may be implemented to mitigate the impact of a pandemic. It is necessary to understand the potential benefits and limitations of each strategy to determine the most appropriate strategies to be implemented. In this article, each strategy is reviewed to define its potential benefits and limitations during a pandemic. Vaccines are probably the most effective measure to reduce morbidity and mortality. However, vaccines are not likely to be available at an early stage of a pandemic. The supply of vaccines is most likely to be insufficient due to limited worldwide production capacity. Antivirals, particularly neuraminidase inhibitors, are expected to be effective against a pandemic influenza strain and are the only available pharmaceutical intervention until enough vaccines are produced. Shortage of supply and high cost is still a major limiting factor in amassing large stockpiles of neuraminidase inhibitors. The possible emergence of resistant strains should also be considered. Nonpharmaceutical interventions can be effective in preventing the spread of the virus under certain conditions. The effectiveness of nonpharmaceutical interventions depends on how influenza viruses are transmitted. There are still significant gaps in the scientific evidence of the way in which influenza viruses are transmitted. Further studies should be conducted to define the basic transmission patterns of influenza viruses.

Febrile respiratory illness in the intensive care unit setting: an infection control perspective

PURPOSE OF REVIEW

We have examined studies published since the severe acute respiratory syndrome outbreak that elucidate the mode of transmission of respiratory pathogens and the optimal means of interrupting their transmission, focusing on transmission in the intensive care unit.

RECENT FINDINGS

The severe acute respiratory syndrome may be transmitted by the droplet, contact and occasionally the airborne route. Transmission occurred most frequently when healthcare workers failed to use standard precautions such as hand washing or personal protective equipment designed to limit droplet and contact transmission. Aerosol-generating procedures increased transmission, but incomplete use of personal protective equipment during procedures was common. Recent publications have stressed the benefits of appropriate staffing levels, the use of single occupancy rooms, the immunization of healthcare workers against influenza, and the importance of healthcare workers remaining home when ill in reducing the morbidity and mortality of respiratory infection within the intensive care unit.

SUMMARY

Most respiratory pathogens can be transmitted by more than one route. Despite this, healthcare worker awareness of clinical syndromes associated with respiratory pathogens that require airborne precautions, combined with the use of standard precautions for all patients, and contact/droplet precautions for patients with undifferentiated febrile respiratory illness should be effective in interrupting the transmission of respiratory pathogens within the intensive care unit.

Interactions between influenza and bacterial respiratory pathogens: implications for pandemic preparedness

It is commonly believed that the clinical and epidemiological characteristics of the next influenza pandemic will mimic those of the 1918 pandemic. Determinative beliefs regarding the 1918 pandemic include that infections were expressed as primary viral pneumonias and/or acute respiratory distress syndrome, that pandemic-related deaths were the end states of the natural progression of disease caused by the pandemic strain, and that bacterial superinfections caused relatively fewer deaths in 1918 than in subsequent pandemics. In turn, response plans are focused on developing and/or increasing inventories of a strain-specific vaccine, antivirals, intensive care beds, mechanical ventilators, and so on. Yet, there is strong and consistent evidence of epidemiologically and clinically important interactions between influenza and secondary bacterial respiratory pathogens, including during the 1918 pandemic. Countermeasures (eg, vaccination against pneumococcal and meningococcal disease before a pandemic; mass uses of antibiotic(s) with broad spectrums of activity against common bacterial respiratory pathogens during local epidemics) designed to prevent or mitigate the effects of influenza-bacterial interactions should be major focuses of pandemic-related research, prevention, and response planning.

Too clean, or not too clean: the hygiene hypothesis and home hygiene

The 'hygiene hypothesis' as originally formulated by Strachan, proposes that a cause of the recent rapid rise in atopic disorders could be a lower incidence of infection in early childhood, transmitted by unhygienic contact with older siblings. Use of the term 'hygiene hypothesis' has led to several interpretations, some of which are not supported by a broader survey of the evidence. The increase in allergic disorders does not correlate with the decrease in infection with pathogenic organisms, nor can it be explained by changes in domestic hygiene. A consensus is beginning to develop round the view that more fundamental changes in lifestyle have led to decreased exposure to certain microbial or other species, such as helminths, that are important for the development of immunoregulatory mechanisms. Although this review concludes that the relationship of the hypothesis to hygiene practice is not proven, it lends strong support to initiatives seeking to improve hygiene practice. It would however be helpful if the hypothesis were renamed, e.g. as the 'microbial exposure' hypothesis, or 'microbial deprivation' hypothesis, as proposed for instance by Bjorksten. Avoiding the term 'hygiene' would help focus attention on determining the true impact of microbes on atopic diseases, while minimizing risks of discouraging good hygiene practice.

A double-blind, randomized, clinical trial of the effect of vitamin A and zinc supplementation on diarrheal disease and respiratory tract infections in children in Mexico City, Mexico

BACKGROUND

The efficacy of micronutrient supplementation in improving childhood health and survival in developing countries may be specific to the micronutrient used and health outcome measured.

OBJECTIVE

We evaluated the effect of vitamin A and zinc supplementation on overall rates of childhood diarrheal disease and respiratory tract infections and rates stratified by household and personal characteristics.

DESIGN

A double-blind, randomized, placebo-controlled trial was carried out in which 736 children aged 6-15 mo living in a periurban area of Mexico City were assigned to receive vitamin A every 2 mo, zinc daily, vitamin A and zinc together, or placebo. Children were followed for 12 mo to determine overall counts of diarrheal episodes and respiratory tract infections.

RESULTS

Vitamin A supplementation was associated with a 27% increase in diarrheal disease [risk ratio (RR): 1.27; 95% CI: 1.10, 1.45; P < 0.001] and a 23% increase in cough with fever (RR: 1.23; 95% CI: 1.02, 1.47; P = 0.02), whereas zinc had no effect on these outcomes. Vitamin A supplementation decreased diarrhea in children from households with dirt floors but increased diarrhea in children from households with nondirt floors, piped water, and indoor bathrooms. Zinc supplementation decreased diarrhea in children from households with dirt floors and whose mothers were more educated. Vitamin A supplementation increased cough with fever in children from less-crowded households that lacked indoor bathrooms and in children of less-educated mothers.

CONCLUSIONS

Vitamin A increases diarrheal disease and respiratory tract infections in young children in periurban areas of Mexico City. Vitamin A and zinc have more heterogeneous effects in different subgroups of children.

A randomized, controlled trial of a multifaceted intervention including alcohol-based hand sanitizer and hand-hygiene education to reduce illness transmission in the home

OBJECTIVE

Good hand hygiene may reduce the spread of infections in families with children who are in out-of-home child care. Alcohol-based hand sanitizers rapidly kill viruses that are commonly associated with respiratory and gastrointestinal (GI) infections. The objective of this study was to determine whether a multifactorial campaign centered on increasing alcohol-based hand sanitizer use and hand-hygiene education reduces illness transmission in the home.

METHODS

A cluster randomized, controlled trial was conducted of homes of 292 families with children who were enrolled in out-of-home child care in 26 child care centers. Eligible families had > or =1 child who was 6 months to 5 years of age and in child care for > or =10 hours/week. Intervention families received a supply of hand sanitizer and biweekly hand-hygiene educational materials for 5 months; control families received only materials promoting good nutrition. Primary caregivers were phoned biweekly and reported respiratory and GI illnesses in family members. Respiratory and GI-illness-transmission rates (measured as secondary illnesses per susceptible person-month) were compared between groups, adjusting for demographic variables, hand-hygiene practices, and previous experience using hand sanitizers.

RESULTS

Baseline demographics were similar in the 2 groups. A total of 1802 respiratory illnesses occurred during the study; 443 (25%) were secondary illnesses. A total of 252 GI illnesses occurred during the study; 28 (11%) were secondary illnesses. The secondary GI-illness rate was significantly lower in intervention families compared with control families (incidence rate ratio [IRR]: 0.41; 95% confidence interval [CI]: 0.19-0.90). The overall rate of secondary respiratory illness was not significantly different between groups (IRR: 0.97; 95% CI: 0.72-1.30). However, families with higher sanitizer usage had a marginally lower secondary respiratory illness rate than those with less usage (IRR: 0.81; 95% CI: 0.65-1.09).

CONCLUSIONS

A multifactorial intervention emphasizing alcohol-based hand sanitizer use in the home reduced transmission of GI illnesses within families with children in child care. Hand sanitizers and multifaceted educational messages may have a role in improving hand-hygiene practices within the home setting.

Airplanes and Infectious Disease

Air travel is associated with crowded conditions that can facilitate the transmission of airborne infectious diseases. The risk of contracting such diseases depends on the presence of an infected person who is shedding infectious particles and sufficient exposure of a sensitive person to achieve an adequate dose to cause disease. Proximity to the infectious person and the length of time spent near the person are the most important risks for contracting a disease. Ventilation patterns play a lesser role in disease transmission. Well-documented outbreaks of influenza, severe acute respiratory syndrome (SARS), and tuberculosis have occurred. Other common respiratory illnesses have probably also been spread via aircraft, but outbreaks remain unrecognized. Research on the spread of infectious disease in aircraft has focused on sampling for microorganisms in air (which has little relevance), and on the development of models to predict the risks for specific diseases.