Lancet: Particle sizes of infectious aerosols: implications for infection control

Fennelley, K. P. (2020) | Particle sizes of infectious aerosols: implications for infection control |The Lancet | DOI:


The global pandemic of COVID-19 has been associated with infections and deaths among health-care workers. This Viewpoint of infectious aerosols is intended to inform appropriate infection control measures to protect health-care workers. Studies of cough aerosols and of exhaled breath from patients with various respiratory infections have shown striking similarities in aerosol size distributions, with a predominance of pathogens in small particles (<5 μm). These are immediately respirable, suggesting the need for personal respiratory protection (respirators) for individuals in close proximity to patients with potentially virulent pathogens. There is no evidence that some pathogens are carried only in large droplets. Surgical masks might offer some respiratory protection from inhalation of infectious aerosols, but not as much as respirators. However, surgical masks worn by patients reduce exposures to infectious aerosols to health-care workers and other individuals. The variability of infectious aerosol production, with some so-called super-emitters producing much higher amounts of infectious aerosol than most, might help to explain the epidemiology of super-spreading. Airborne infection control measures are indicated for potentially lethal respiratory pathogens such as severe acute respiratory syndrome coronavirus.

Full paper from The Lancet

Pandemic peak SARS-CoV-2 infection and seroconversion rates in London frontline health-care workers #covid19rftlks

Houlihan, C. F., et al. |2020| Pandemic peak SARS-CoV-2 infection and seroconversion rates in London frontline health-care workers|Lancet (London, England).

Nosocomial transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a major public health concern. Health-care workers (HCWs) are at high risk of developing COVID-19, and may themselves contribute to transmission.

To evaluate these risks, the experts behind this study enrolled 200 patient-facing HCWs between March 26 and April 8, 2020, in SARS-CoV-2 Acquisition in Frontline Healthcare Workers—Evaluation to inform Response (SAFER), a prospective cohort study in high-risk frontline HCWs in an acute National Health Service hospital trust in London. We collected nasopharyngeal swabs for RT-PCR twice per week, symptom data, and blood samples monthly for high-sensitivity serology assays (ELISA and flow cytometry for spike glycoprotein).

The authors compared the risk of SARS-CoV-2 positive disease by RT-PCR detection
in the 1 month of follow-up in those who tested negative by serology and RT-PCR at baseline (122 of 181 HCWs) with those who were positive by serology and negative by RT-PCR at baseline (33 of 181 HCWs).

These data highlight the urgent need to implement policies to better protect HCWs and for regular asymptomatic HCW surveillance in hospital settings that will protect both HCW staff and patients from nosocomial transmission through a potential SARS-CoV-2 second wave. Vaccines, if and when they become available, should initially be prioritised for HCWs.

Full article available to read from The Lancet

Face coverings mandatory in shops, supermarkets, shopping centres and transport hubs

Under new regulations members of the public will need to wear face coverings – for example, a fabric covering, scarf or bandana – that covers the nose and mouth in additional enclosed public spaces, as well as frequent hand washing and careful social distancing.

  • Face coverings will be mandatory in additional enclosed public spaces from Friday 24 July – including shops, supermarkets, shopping centres and transport hubs
  • New measure an important step in lifting lockdown, as the public are encouraged to play their part
  • Venues such as restaurants, pubs and gyms will be exempt

Full detail: Face coverings mandatory in shops, supermarkets, shopping centres and enclosed transport hubs from 24th July  | Department of Health

Clinical guidance for healthcare professionals on maintaining immunisation programmes during COVID-19

Public Health England | updated 29th June 2020

NHS England and NHS Improvement, together with Public Health England, has published clinical guidance for healthcare professionals on maintaining our NHS immunisation programmes during COVID-19.

It gives advice on how to approach some of the specific challenges practices may face and includes a series of FAQs that can be used in communication with the public. The production of the guidance has been supported by the Royal College of General Practitioners (RCGP) and the Royal College of Paediatrics and Child Health (RCPCH).

Full guidance: Clinical guidance for healthcare professionals on maintaining immunisation programmes during COVID-19

Patients endangered by ‘hazardous’ use of PPE

via HSJ | 3rd July 2020

The “hazardous” use of personal protective equipment required because of Covid-19 is contributing to the spread of secondary infections in intensive care units and other hospital settings, a leading expert has told HSJ.

Infection Prevention Society vice president Professor Jennie Wilson, said: “[PPE] has been used to protect the staff, but the way it has been used has increased the risk of transmission between patients. The widespread use of PPE particularly in critical care environments has exacerbated the problem (of patient to patient transmission). Unless we tackle the approach to PPE we will continue to see this major risk of transmission of infections between patients.”

Full article: Patients endangered by ‘hazardous’ use of PPE

Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis

Liang, M. (2020). Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis.



Conflicting recommendations exist related to whether masks have a protective effect on the spread of respiratory viruses.


The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement was consulted to report this systematic review. Relevant articles were retrieved from PubMed, Web of Science, ScienceDirect, Cochrane Library, and Chinese National Knowledge Infrastructure (CNKI), VIP (Chinese) database.


A total of 21 studies met our inclusion criteria. Meta-analyses suggest that mask use provided a significant protective effect (OR = 0.35 and 95% CI = 0.24–0.51). Use of masks by healthcare workers (HCWs) and non-healthcare workers (Non-HCWs) can reduce the risk of respiratory virus infection by 80% (OR = 0.20, 95% CI = 0.11–0.37) and 47% (OR = 0.53, 95% CI = 0.36–0.79). The protective effect of wearing masks in Asia (OR = 0.31) appeared to be higher than that of Western countries (OR = 0.45). Masks had a protective effect against influenza viruses (OR = 0.55), SARS (OR = 0.26), and SARS-CoV-2 (OR = 0.04). In the subgroups based on different study designs, protective effects of wearing mask were significant in cluster randomized trials and observational studies.


This study adds additional evidence of the enhanced protective value of masks, we stress that the use masks serve as an adjunctive method regarding the COVID-19 outbreak.

Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis

Antibody tests for identification of current and past infection with SARS‐CoV‐2

This Cochrane systematic review finds that, when it comes to antibody testing for covid-19, timing is everything. The review of 54 studies found that antibody tests carried one week after a patient first developed symptoms detected only 30% of people who had covid-19. Accuracy increased in to 72% at two weeks and to 94% in the third week.

The review shows that antibody tests could have a useful role in detecting if someone has had COVID‐19, but the timing of when the tests are used is important.

Antibody tests may help to confirm COVID‐19 infection in people who have had symptoms for more than two weeks and do not have a RT‐PCR test, or have negative RT‐PCR test results. The tests are better at detecting COVID‐19 in people two or more weeks after their symptoms started, but we do not know how well they work more than five weeks after symptoms started.

We do not know how well the tests work for people who have milder disease or no symptoms, because the studies in the review were mainly done in people who were in hospital. In time, we will learn whether having previously had COVID‐19 provides individuals with immunity to future infection.

Further research is needed into the use of antibody tests in people recovering from COVID‐19 infection, and in people who have experienced mild symptoms or who never experienced symptoms

Full article: Antibody tests for identification of current and past infection with SARS‐CoV‐2 | Cochrane Database of Systematic Reviews 2020, Issue 6 | 25th June 2020


Getting back on track: control of covid-19 outbreaks in the community

This analysis suggests there’s still time to change tack on the UK’s ad hoc system for covid-19 tracking, testing, and contact tracing | BMJ | 2020; 369: m2484 

Key messages

  • England’s established system of local communicable disease control has been eroded over several decades
  • In response to covid-19 the government has created a parallel system which steers patients away from GPs and relies on commercial companies for testing and contact tracing
  • Many suspected cases will have been missed because of mishandling of the notification system
  • NHS 111 covid-19 call centres and the covid-19 clinical assessment service should be reintegrated immediately into primary care and practices resourced to resume care
  • Contact tracing and testing should be led by local authorities and coordinated nationally
  • England must rebuild and reintegrate its local communicable disease control system

Full detail: Getting back on track: control of covid-19 outbreaks in the community

First volunteer receives Imperial COVID-19 vaccine #covid19rftlks

via Imperial College London | 23rd June 2020

The first healthy volunteer has now received a candidate coronavirus vaccine developed by Imperial researchers. The clinical team, who delivered a small dose of the vaccine to the participant at a West London facility, are closely monitoring the participant and report they are in good health, with no safety concerns.

Imperial College London’s vaccine candidate is being developed and trialled thanks to more than £41 million in funding from the UK government and a further £5 million in philanthropic donations.

The trials are the first test of a new self-amplifying RNA (saRNA) technology, which has the potential to revolutionise vaccine development and enable scientists to respond more quickly to emerging diseases.

The vaccine has undergone rigorous pre-clinical safety tests and in animal studies it has been shown to be safe and produced encouraging signs of an effective immune response.

Full detail: First volunteer receives Imperial COVID-19 vaccine


What is the evidence to support the 2-metre social distancing rule to reduce COVID-19 transmission?

Centre for Evidence-Based Medicine | 22nd June 2020

  • The 2-metre social distancing rule assumes that the dominant routes of transmission of SARS-CoV-2 are via respiratory large droplets falling on others or surfaces.
  • A one-size-fits-all 2-metre social distancing rule is not consistent with the underlying science of exhalations and indoor air. Such rules are based on an over-simplistic picture of viral transfer, which assume a clear dichotomy between large droplets and small airborne droplets emitted in isolation without accounting for the exhaled air. The reality involves a continuum of droplet sizes and an important role of the exhaled air that carries them.
  • Smaller airborne droplets laden with SARS-CoV-2 may spread up to 8 metres concentrated in exhaled air from infected individuals, even without background ventilation or airflow. Whilst there is limited direct evidence that live SARS-CoV-2 is significantly spread via this route, there is no direct evidence that it is not spread this way.
  • The risk of SARS-CoV-2 transmission falls as physical distance between people increases, so relaxing the 2-metre rule, particularly for indoor settings, might therefore risk an increase in infection rates. In some settings, even 2 metres may be too close.
  • Safe transmission mitigation measures depend on multiple factors related to both the individual and the environment, including viral load, duration of exposure, number of individuals, indoor versus outdoor settings, level of ventilation and whether face coverings are worn.
  • Social distancing should be adapted and used alongside other strategies to reduce transmission, such as air hygiene, involving in part maximizing and adapting ventilation  to specific indoor spaces, effective hand washing, regular surface cleaning, face coverings where appropriate and prompt isolation of affected individuals.

Full detail: What is the evidence to support the 2-metre social distancing rule to reduce COVID-19 transmission?