Practical Indicators for Risk of Airborne Transmission in Shared Indoor Environments and Their Application to COVID-19 Outbreaks.

Some infectious diseases, including COVID-19, can undergo airborne transmission. This may happen at close proximity, but as time indoors increases, infections can occur in shared room air despite distancing. We propose two indicators of infection risk for this situation, that is, relative risk parameter (Hr) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and aerosol-removal rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend that is consistent with airborne infection and enable recommendations to minimize transmission risk. Transmission in typical prepandemic indoor spaces is highly sensitive to mitigation efforts. Previous outbreaks of measles, influenza, and tuberculosis were also assessed. Measles outbreaks occur at much lower risk parameter values than COVID-19, while tuberculosis outbreaks are observed at higher risk parameter values. Because both diseases are accepted as airborne, the fact that COVID-19 is less contagious than measles does not rule out airborne transmission. It is important that future outbreak reports include information on masking, ventilation and aerosol-removal rates, number of occupants, and duration of exposure, to investigate airborne transmission.

Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

The coronavirus disease 2019 (COVID-19) pandemic has caused untold disruption throughout the world. Understanding the mechanisms for transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is key to preventing further spread, but there is confusion over the meaning of 'airborne' whenever transmission is discussed. Scientific ambivalence originates from evidence published many years ago which has generated mythological beliefs that obscure current thinking. This article collates and explores some of the most commonly held dogmas on airborne transmission in order to stimulate revision of the science in the light of current evidence. Six 'myths' are presented, explained and ultimately refuted on the basis of recently published papers and expert opinion from previous work related to similar viruses. There is little doubt that SARS-CoV-2 is transmitted via a range of airborne particle sizes subject to all the usual ventilation parameters and human behaviour. Experts from specialties encompassing aerosol studies, ventilation, engineering, physics, virology and clinical medicine have joined together to produce this review to consolidate the evidence for airborne transmission mechanisms, and offer justification for modern strategies for prevention and control of COVID-19 in health care and the community.

[The mechanism of hyperbaric oxygen regulating HMGB1 in the prevention and treatment of encephalopathy after acute CO poisoning].

Objective: To study the expression of high mobility group protein 1 (HMGB1) in the brain of rats after hyperbaric oxygen (HBO) treatment of acute carbon monoxide poisoning (DEACMP) , and to explore the mechanism of HBO in the prevention and treatment of DEACMP pathological process by regulating HMGB1. Methods: 108 SD rats were randomly divided into control group (NC group) and co group (CO group) . HBO treatment group (HBO group) , 48 rats in each group. Co group and HBO group were used to establish CO poisoning model, HBO group were treated with hyperbaric oxygen once a day. Water maze test was used to detect and analyze the memory retention ability of three groups of rats in 3 d, 7 d, 14 d. ELISA was used to detect the plasma concentration of HMGB1、IL-6、TNF-α in three groups of rats on the 1 d, 3 d, 7 d, 14 d, 21 d Concentration. Western blotting was used to detect the expression of HMGB1 and Caspase-3 in the brain of the three groups on the 1 d, 3 d, 7 d, 14 d, 21 d. TUNEL staining was used to detect the apoptosis of hippocampal neurons in the three groups. Results: Compared with NC group, the average escape latency of rats in CO group and HBO group was significantly prolonged, and the activity time of platform quadrant in CO group was significantly shortened on 14 d and 21 d (P<0.05) ; compared with CO group, the average escape latency of HBO group on 7 d, 14 d and 21 d was significantly shortened (P<0.05) . Compared with NC group, plasma HMGB1 in CO group and HBO group were significantly increased (P<0.05) ; after 3 days, HBO group was significantly lower than co group, the difference was statistically significant (P<0.05) . The levels of IL-6 and TNF-α in HBO group and co group increased rapidly and then decreased gradually. The increased levels of IL-6 and TNF-α in HBO group were significantly lower than those in CO group (P<0.05) . Compared with NC group, the expression of HMGB1 and Caspase-3 in CO group was significantly increased on 3 d, 7 d and 14 d (P<0.05) ; the expression of HMGB1 and Caspase-3 in HBO group was significantly increased on 3 d, 7 d, 14 d and 21 d (P<0.05) ; compared with CO group, the expression of HMGB1 and Caspase-3 in HBO group decreased significantly on 3 d, 7 d, 14 d and 21 d (P<0.05) . The apoptotic index of nerve cells in CO group began to increase at 3 days, which was significantly different from that of NC group (P<0.05) , and the difference was still statistically significant on 21 d (P<0.05) ; the apoptotic index of nerve cells in HBO group was slightly increased, but there was no significant difference compared with NC group (P>0.05) , and the apoptotic index of 3 d, 7 d, 14 d and 21 d in HBO group was significantly lower than that in CO group (P<0.05) . Conclusion: acute CO poisoning can induce the release of HMGB1 and a variety of inflammatory factors. HMGB1 can promote the apoptosis of nerve cells after acute CO poisoning by up regulating the expression of caspase-3 protein, and participate in the pathological process of DEACMP. HBO can down regulate the expression of HMGB1, IL-6, TNF-α and caspase-3 protein, inhibit the apoptosis of nerve cells, and play a protective role on nerve cells.

Inferring super-spreading from transmission clusters of COVID-19 in Hong Kong, Japan, and Singapore.

Super-spreading events in an outbreak can change the nature of an epidemic. Therefore, it is useful for public health teams to determine whether an ongoing outbreak has any contribution from such events, which may be amenable to interventions. We estimated the basic reproductive number (R0) and the dispersion factor (k) from empirical data on clusters of epidemiologically linked coronavirus disease 2019 (COVID-19) cases in Hong Kong, Japan and Singapore. This allowed us to infer the presence or absence of super-spreading events during the early phase of these outbreaks. The relatively large values of k implied that large cluster sizes, compatible with super-spreading, were unlikely.

Evaluating the aptima HIV-1 quant Dx, HCV quant Dx and HBV quant assays against the Abbott HIV-1, HCV and HBV RealTime assays.

BACKGROUND: Viral load measurement is routine for the management of patients infected with HIV, HCV or HBV, using sensitive, quantitative, nucleic acid amplification tests (NAATs). However, platforms are not equivalent in terms of turnaround time, random access capability and operator hands-on time. OBJECTIVES AND STUDY DESIGN: We compared the performance of the Hologic Panther transcription-mediated amplification based Aptima assays for HIV, HBV and HCV viral load measurement with the corresponding Abbott m2000 RealTime assays. All Aptima assays were run according to the manufacturer's instructions, on archived patient samples for HIV (n = 251 including subtypes 01_AE, A (A1), B, BG recombinant, C CRF02_AG and G), HBV (n = 117 including genotypes A, B, C and D) and HCV (n = 82 including genotypes 1, 2, 3 and 4). Additional testing was performed with WHO international standards and expanded HIV-1 subtype and HCV NIBSC genotype panels. RESULTS: The Hologic Panther Aptima assays for HIV-1 RNA, HBV DNA and HCV RNA viral load measurements performed equivalently to the Abbott m2000 RealTime assays. The performance of the Aptima assays was also acceptable on the WHO and NIBSC standards and subtype/genotype panels. CONCLUSIONS: The Aptima Panther platform offers equivalent clinical performance for the viral load measurement of these three viruses, with the added benefits of reduced turnaround time, random access capability and reduced 'hands-on time' for staff, resulting in a potentially superior workflow for diagnostic laboratories.

Transmission routes of influenza A(H1N1)pdm09: analyses of inflight outbreaks.

Knowledge about the infection transmission routes is significant for developing effective intervention strategies. We searched the PubMed databases and identified 10 studies with 14 possible inflight influenza A(H1N1)pdm09 outbreaks. Considering the different mechanisms of the large-droplet and airborne routes, a meta-analysis of the outbreak data was carried out to study the difference in attack rates for passengers within and beyond two rows of the index case(s). We also explored the relationship between the attack rates and the flight duration and/or total infectivity of the index case(s). The risk ratios for passengers seated within and beyond the two rows of the index cases were 1.7 (95% confidence interval (CI) 0.98-2.84) for syndromic secondary cases and 4.3 (95% CI 1.25-14.54) for laboratory-confirmed secondary cases. Furthermore, with an increase of the product of the flight duration and the total infectivity of the index cases, the overall attack rate increased linearly. The study indicates that influenza A(H1N1)pdm09 may mainly be transmitted via the airborne route during air travel. A standardised approach for the reporting of such inflight outbreak investigations would help to provide more convincing evidence for such inflight transmission events.

Probable transmission routes of the influenza virus in a nosocomial outbreak.

Influenza is a long-standing public health concern, but its transmission remains poorly understood. To have a better knowledge of influenza transmission, we carried out a detailed modelling investigation in a nosocomial influenza outbreak in Hong Kong. We identified three hypothesised transmission modes between index patient and other inpatients based on the long-range airborne and fomite routes. We considered three kinds of healthcare workers' routine round pathways in 1140 scenarios with various values of important parameters. In each scenario, we used a multi-agent modelling framework to estimate the infection risk for each hypothesis and conducted least-squares fitting to evaluate the hypotheses by comparing the distribution of the infection risk with that of the attack rates. Amongst the hypotheses tested in the 1140 scenarios, the prediction of modes involving the long-range airborne route fit better with the attack rates, and that of the two-route transmission mode had the best fit, with the long-range airborne route contributing about 94% and the fomite route contributing 6% to the infections. Under the assumed conditions, the influenza virus was likely to have spread via a combined long-range airborne and fomite routes, with the former predominant and the latter negligible.

The multi-faceted dynamics of HIV-1 transmission in Northern Alberta: A combined analysis of virus genetic and public health data.

Molecular epidemiology has become a key tool for tracking infectious disease epidemics. Here, the spread of the most prevalent HIV-1 subtypes in Northern Alberta, Canada, was characterized with a Bayesian phylogenetic approach using 1146 HIV-1 pol sequences collected between 2007 and 2013 for routine clinical management purposes. Available patient metadata were qualitatively interpreted and correlated with onwards transmission using Fisher exact tests and logistic regression. Most infections were from subtypes A (n=36), B (n=815) and C (n=211). Africa is the dominant origin location for subtypes A and C while the subtype B epidemic was seeded from the USA and Middle America and, from the early 1990s onwards, mostly by interprovincial spread. Subtypes A (77.8%) and C (74.0%) were usually heterosexually transmitted and circulate predominantly among Blacks (61.1% and 85% respectively). Subtype B was mostly found among Caucasians (48.6%) and First Nations (36.8%), and its modes of transmission were stratified by ethnic origin. Compared to subtypes A (5.6%) and C (3.8-10.0%), a larger portion of subtype B patients were found within putative provincial transmission networks (20.3-29.5%), and this almost doubled when focusing on nationwide transmission clusters (37.9-57.5%). No clear association between cluster membership and particular patient characteristics was found. This study reveals complex and multi-faceted transmission dynamics of the HIV-1 epidemic in this otherwise low HIV prevalence population in Northern Alberta, Canada. These findings can aid public health planning.

Resource impact of managing suspected Middle East respiratory syndrome patients in a UK teaching hospital.

Clinical challenges exist in the management of hospitalized patients returning to the UK with potential Middle East respiratory syndrome coronavirus (MERS-CoV) infection, particularly with its clinical overlap with influenza, as demonstrated in this case-series and cost-analysis review of returning Hajj pilgrims. These patients were hospitalized with acute febrile respiratory illness, initially managed as potential MERS-CoV infections, but were eventually diagnosed with influenza. Additional costs were small, yet enhanced infection prevention measures created significant burdens on isolation rooms and staff time. Planning for predictable events such as Hajj is important for resource management. Here, in-house MERS-CoV diagnostic testing would have facilitated earlier diagnosis and discharge.

Influenza virus survival in aerosols and estimates of viable virus loss resulting from aerosolization and air-sampling.

Using a Collison nebulizer, aerosols of influenza (A/Udorn/307/72 H3N2) were generated within a controlled experimental chamber, from known starting virus concentrations. Air samples collected after variable suspension times were tested quantitatively using both plaque and polymerase chain reaction assays, to compare the proportion of viable virus against the amount of detectable viral RNA. These experiments showed that whereas influenza RNA copies were well preserved, the number of viable viruses decreased by a factor of 10(4)-10(5). This suggests that air-sampling studies for assessing infection control risks that detect only influenza RNA may greatly overestimate the amount of viable virus available to cause infection.