Models show big infection risks in ‘low risk’ office work

New studies from the UK and the US, modelling virus risks in offices and other indoor environments, have concluded there is a potentially substantial risk of Covid-19 infection. Matthew J Evans of the Massachusetts Institute of Technology, who modelled Covid-19 aerosol transmission and used the findings to propose guidelines for ventilation and occupancy in the workplace, concluded: “Avoiding infection requires good ventilation and/or short exposure times. Generally, office spaces should not be occupied by more than one person.” Evans noted “a substantial body of literature has developed over the last few decades showing that the short-range aerosol route is an important, though often neglected transmission path.” Much of the current workplace guidance on social distancing and provision of personal protective equipment is based on close range ‘droplet transmission’ alone.

Professor Clive Beggs of Leeds Beckett University, who also considered this issue, noted that unlike droplets, aerosols can “be widely distributed throughout room spaces.” He said the findings of his computer modelling study, which simulated transmission in an office building, “suggest that individuals who share enclosed spaces with an infector may be at risk of contracting Covid-19 by the aerosol route, even when practising social distancing.”
Read more: 

  • Matthew J Evans. Avoiding Covid-19: Aerosol guidelines [Full article pdf], medRxiv preprint, 25 May 2020. 
  • Clive B Beggs. Is there an airborne component to the transmission of COVID-19? : a quantitative analysis study, [Full article pdfmedRxiv preprint, 25 May 2020.
    Source: Risks 949

WHO review concluded medical workers should wear respirators, not surgical masks

A World Health Organisation (WHO) commissioned review published on Monday in the Lancet has found the organisation has been dangerously wrong on respirators and physical distancing, points raised repeatedly with WHO by ITUC and global unions. WHO so far has refused to move on either issue, and defended both positions in a 29 May 2020 WHO webinar.

The  new analysis of 172 studies confirms what scientists have said for months: N95 and other respirator masks are far superior to surgical or cloth masks in protecting essential medical workers against the coronavirus. The WHO-funded Lancet review concludes respirators should the ‘minimum’ protection for health care workers (WHO currently only recommends respirators in the highest risk activities).  The results make it clear that the WHO. and the Centers for Disease Control and Prevention should recommend that essential workers like nurses and emergency responders wear N95 masks, not just surgical masks, experts said.

It also notes there is a 2.6 per cent transmission/infection risk at 1 metre physical distancing; this risk halves at 2 metres (WHO currently recommends ‘at least 1m’). In Australia we seem to have settled on 1.5 metres - exactly half way.

Read more: Derek K Chu, et al, on behalf of the COVID-19 Systematic Urgent Review Group Effort (SURGE) study authors. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis, [Full paper pdf] published online June 1, 2020. 1

Does temperature and humidity affect spread of coronavirus

The link between seasonal variation and viral outbreaks is much debated. It is thought that cold temperatures increase viral half-lives and that low relative humidity (RH) adversely influences natural processes that otherwise lead to viral inactivation. Consequently, there is a growing interest in whether indoor temperature and RH may be modifiable risk factors for aerial transmission of viruses.

There have been some preclinical studies and observational data which suggest that high temperature as well as RH in the 40%–60% range may reduce transmission of the novel coronavirus (COVID-19). And although high humidity has been shown to reduce transmission of various other aerosolised viruses, once RH exceeds 60%, the likelihood of mould growth increases significantly.

At present, various regulatory bodies in the USA suggest that during winter months, indoor temperature should be maintained between 20°C and 24°C, while RH should be maintained between 20% and 60%.

In a short 'post script' in the Journal of Occupational and Environmental Medicine, the US researchers conclude: "While definitive evidence to support the benefits of maintaining higher indoor temperatures as well as RH between 40% and 60% is still needed, hospitals may want to consider routinely measuring indoor climate since optimising these parameters may be a relatively simple, low-cost intervention to potentially decrease the risk of aerial transmission of viruses among healthcare providers and patients."
Read more: Medical Workers Should Use Respirators, Not Surgical Masks, The New York Times. Sadeq A Quraishi, Lorenzo Berra, Ala Nozari, Indoor temperature and relative humidity in hospitals: workplace considerations during the novel coronavirus pandemic [Full article], BMJ OEM

Male melanoma risk in Australia

Recent research by the QIMR Berghofer Medical Research Institute has found that the melanoma risk to Australian men increases as they age, with their incidence rate exceeding that of women by the time they reach 45. This gender difference appears sooner in Australia than other countries (e.g. Denmark's gender difference started showing at 65 years). 

Drawing on cancer registry data, the QIMR research team looked at fair-skinned populations exposed to different levels of UV in eight different countries (Australia, New Zealand, the US, Canada, the UK, Sweden, Norway and Denmark) over three decades. Globally women of all ages are more likely than men to develop melanoma of the lower limbs while men are more likely to develop melanomas of the head, neck and trunk. In Australia, men are twice as likely to develop melanomas of the head and neck and two and half times more likely to develop melanoma on the trunk than Australian women.
Read more: Catherine M. Olsen; John F. Thompson; Nirmala Pandeya; et al, Evaluation of Sex-Specific Incidence of Melanoma [AbstractJAMA Dermatology. Source: Cancer Council

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