Through infected persons or surfaces, but airborne transmission unlikely
Transmission of the COVID-19 virus can occur by direct contact with infected people and indirect contact with surfaces in the immediate environment or with objects used on the infected person, the World Health Organisation (WHO) said in a scientific brief released on 27 March.
According to current evidence, COVID-19 virus is transmitted between people through respiratory droplets and contact routes.
Droplet transmission occurs when a person is in close contact, within a metre, with someone who has respiratory symptoms and is therefore at risk of having the mouth and nose or eyes exposed to potentially infective respiratory droplets.
Droplet transmission may also occur through objects or materials which are likely to carry infection, such as clothes, utensils, and furniture, in the immediate environment around the infected person.
Microbes may remain in the air for long periods of time and be transmitted to others over distances greater than 1 meter. In the context of COVID-19, airborne transmission may be possible in specific circumstances and settings in which procedures that generate aerosols are performed (mostly in medical settings).
An analysis of 75,465 COVID-19 cases in China, airborne transmission was not reported.
There is some evidence that COVID-19 infection may lead to intestinal infection and be present in faeces. However, to date, only one study has cultured the COVID-19 virus from a single stool specimen. There have been no reports of faecal-oral transmission of the COVID-19 virus to date.
To date, some scientific publications provide initial evidence of whether the COVID-19 virus can be detected in the air and thus, potentially involve airborne transmission. These initial findings need to be interpreted carefully.
A recent publication in the has evaluated virus persistence of the COVID-19 virus. In this experimental study, aerosols were generated using under controlled laboratory conditions, using a high-powered machine that does not reflect normal human cough conditions.
Based on the available evidence, including the recent publications, WHO continues to recommend droplet and contact precautions for those people caring for COVID-19 patients and contact and airborne precautions for circumstances and settings in which aerosol-generating procedures are performed.
At the same time, other countries and organisations, including the US Centers for Diseases Control and Prevention and the European Centre for Disease Prevention and Control, recommend airborne precautions for any situation involving the care of COVID-19 patients and consider the use of medical masks as an acceptable option in case of shortages of respirators (N95, FFP2 or FFP3).
Current WHO recommendations emphasise the importance of rational and appropriate use of all PPE, not only masks, which requires correct and rigorous behaviour from health care workers, particularly in doffing procedures and hand hygiene practices.
WHO also recommends staff training on these recommendations, as well as the adequate procurement and availability of the necessary PPE and other supplies and facilities.
WHO continues to emphasise the utmost importance of frequent hand hygiene, respiratory etiquette, and environmental cleaning and disinfection, as well as the importance of maintaining physical distances and avoidance of close, unprotected contact with people with fever or respiratory symptoms.