22nd Sep 2020 @ 9:15 am

The outdoor life and breezy climate of the Canaries could turn out to be a distinct health advantage, recent research on Covid-19 transmission suggests. 

New research concerning the transmission of Covid-19 shows that experts are increasingly believing that the virus is transmitted by tiny droplets called aerosols, especially in crowded, unventilated rooms.

When somebody sneezes or coughs, they produce larger respiratory droplets, which fall to the floor quickly; and smaller, lighter droplets called aerosols that may remain in the air for several minutes and travel further than two metres. So far, most advice on avoiding Covid-19 has focused on transmission by respiratory droplets:  distancing requirements reflect how far these droplets can travel, for example. Other advice relates to droplets that land on shared surfaces, such as door handles or telephones, and which are eliminated by disinfection and hand-washing.  

However, airborne transmission via aerosols is gradually becoming more central to the guidelines produced by health authorities.  Last weekend, the American Commission for Disease Control (CDC)  posted official guidance stating that “respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks, or breathes…are thought to be the main way the virus spreads.”

The CDC took down the advice on Monday, saying that it had been posted by mistake and that revised guidelines will follow soon, but the recognition of aerosols reflects an increasing volume of recent research suggesting that airborne transmission is an important factor in the spread of the virus.

The World Health Organisation recognised transmission by aerosols in July, before which it had focused almost entirely on respiratory droplets and infected surfaces. Its current advice states: “There have been reported outbreaks of COVID-19 in some closed settings, such as restaurants, nightclubs, places of worship or places of work where people may be shouting, talking, or singing. In these outbreaks, aerosol transmission, particularly in these indoor locations where there are crowded and inadequately ventilated spaces where infected persons spend long periods of time with others, cannot be ruled out. More studies are urgently needed to investigate such instances and assess their significance for transmission of COVID-19.”

An increased focus on aerosol transmission could have important consequences on future measures to control the virus. An increased focus on outdoor living and adequate ventilation could be central to this advice,. The Canarian Government’s protocols for schools already include recommendations to open windows and ventilate classrooms at all times when this is practical.

The findings also suggest that, while wearing face masks indoors may be an effective way of reducing aerosol infection, outdoor mask use may not be necessary as long as distancing is observed.

Professor Devi Sridhar, who advises the Scottish Government’s Covid response, has written  “as a scientist…my main advice is to get outside as much as possible when seeing other people. Research has shown that 97% of “super-spreading events” occur  indoors, and that outdoor transmission is minimal. If an indoor setting is poorly ventilated, crowded and no one is wearing face coverings, it is best to avoid it.”