What information we have about transmission of COVID-19 in detail?

Question

A lot of information we have how the COVID-19 virus spreads in general. But what do we know about the detected and proven way of transmission:

• about which items (door handles, plates, salad bar, ...) or
• via which exact air route (large office?, in restaurant, with/without air conditioning, ...)
• via which direct human-human contact (handshake, kiss?, ...)
• or other?

There is a study on the spread in nursing homes. It describes whether and when people fell ill. There were also surveys, but unfortunately without information about where and how someone got infected. Especially when the exact day of an infection is determined, the circumstances should also be considered. Many, many messages we read, but no information about the exact way of transmission is available.

On the cruise ship Ruby princess are described 11 cases of secondary transmission. Secondary transmissions should be easily tracked because the 2 persons transmitter and receiver can be easily identified. A follow-up report seems not to be available.

Here, a large number of infections are examined and even subdivided where they originated in: homes, transport, food, entertainment, shopping and miscellaneous. However, it is not specified how the transmission was there in detail.

There are many presumptions about the possible ways of transmission. But which ways was proven already by the many surveys?

Answer 1

This question may a bit too broad (e.g. there are some separate questions about Covid-19 and food) but on the topic of transmission in an office-like setting there have been some studies/reports, some more systematic/formal than others.

I know of a study in South Korea in an office building, call center more precisely, (this has received widespread press coverage; e.g. CNN, BI) and of some press reports of the first known cases in Germany, which also involved transmission in an office setting.

I think we don't know what the minimum contact time for infection to occur was, but some of the details reported:

For example, case #1 - the first person in Germany to be infected by the Chinese woman - sat next to her in a meeting in a small room on Jan. 20, the scientists wrote. [...]

By following all these links, they discovered that case #4 had been in contact several times with the Shanghai patient. Then case #4 sat back-to-back with a colleague in the canteen.

When that colleague turned to borrow the salt, the scientists deduced, the virus passed between them. The colleague became case #5.

So yeah, "pass the salt" was apparently enough in one case for transmission to occur (Reuters actually used that as their article title.)

The Korean call center case was bit more complicated because it involved a large shared space... and elevators. So they could never hope to achive a similar degree of precision in tracing whom gave it to whom in that kind of environment, but...

The first case-patient with symptom onset, who worked in an office on the 10th floor (and reportedly never went to 11th floor), had onset of symptoms on February 22. The second case-patient with symptom onset, who worked at the call center on the 11th floor, had onset of symptoms on February 25. Residents and employees in building X had frequent contact in the lobby or elevators. We were not able to trace back the index case-patient to another cluster or an imported case. [...]

Nearly all the case-patients were on one side of the building on 11th floor. Severe acute respiratory syndrome coronavirus, the predecessor of SARS-CoV-2, exhibited multiple superspreading events in 2002 and 2003, in which a few persons infected others, resulting in many secondary cases. Despite considerable interaction between workers on different floors of building X in the elevators and lobby, spread of COVID-19 was limited almost exclusively to the 11th floor, which indicates that the duration of interaction (or contact) was likely the main facilitator for further spreading of SARS-CoV-2.