Although originating from animals, COVID-19 is now considered to be an indirect zoonosis, as its transmission is now primarily human-to-human.
It is predominantly transmitted in a similar way to the common cold, via contact with droplets of infected individuals' upper respiratory tract secretions, e.g. from sneezing or coughing.
A recent Bayesian regression model has found that aerosol and fomite transmission are plausible.
Orofecal spread was seen with the SARS epidemic, and although it remains unclear if SARS-CoV-2 can be transmitted in this way, there is some evidence for it.
Sexual transmission has not been seen in the field but remains possible, not least because the SARS-CoV-2 virus has been found in all bodily secretions including seminal and vaginal fluids.
It remains unclear if COVID-19 could be transmitted through a blood transfusion although no cases have yet be seen. Nevertheless, many national bodies have instituted controls to reduce the chance of this happening including advising that potential donors do not give blood until 28 days after recovering from COVID-19.
Cohort studies have been unable to rule out the possibility of vertical transmission, but it seems to be a rare event if it does occur. A large prospective cohort study of 427 pregnant women from all 194 birth units across the UK found that 5% of 265 live births were confirmed as COVID-19 on RT-PCR.
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