The vast, vast majority of reported cases are in China. What we know for sure about those cases is that we can't trust the "official" reports. I doubt there's a way to know what's really going on.
There is a corona virus research facility near the Wuhan outbreak epicenter. No way to know if that's really the source.
Rumors it came from an icky "wet market" where their weirdo culture sells things like bats for food. Rumors the exotic mammal the pangolin is a vector. Who knows?
There are reports from China that health workers are being infected in spite of wearing protective clothing. Are they true? How can that happen -- Are they wearing wrong-quality masks, or are the virus particles fantastically tiny and able to pass through or what?
Experts are uncertain whether COVID19 (the new official name) can even be transmitted "airborne" through aerosolized sneeze or cough droplets lingering in the air in the first place.
There is evidence COVID19 can be found in fecal matter from infected persons, but it's unclear whether this can be a source of transmission.
A report from a hotel or apartment in Hong Kong suggests the virus can be transmitted through plumbing, as was also true of SARS (another in the corona virus family).
It is unclear how infectious COVID19 is. Infectiousness is measured by "R0" (usually pronounced "R-nought"). Flu typically has an R0 of about 1.3, meaning each person infected with flu will on average infect 1.3 other people. SARS has an R0 somewhat less than 1. Same with MERS. There is some consensus that COVID19 has R0 of about 2.2 or 2.3, but no one really knows; estimates range from less than 1 to something like 4.75.
Mortality rate is uncertain. So far, all reported deaths have been in China, and their reporting is unreliable. Based on their dubious numbers, mortality is about 2% or 1 in 50. That is higher than flu (I can't find good numbers for flu) but lower than SARS (1 in 10) or MERS (maybe over 1 in 3).
It is uncertain whether the virus can be transmitted to and from pets. (This Newsweek article
makes the silly recommendation that, just on general principles, people should wash their hands thoroughly for at least 20 seconds after handling pets. If it were determined that such practice were really important, no one would ever again own pets. Hell, I sleep with my cat, with her face right next to mine! The same article insists we wash our hands thoroughly for 20 seconds any time we blow our noses, and *immediately* throw away the tissue; and that we always cough into a tissue or our elbow. I have allergies, which includes chronic cough. I cover my cough when I'm around humans. If I coughed into my elbow literally *every* time I cough, I'd need shoulder surgery. I'd have to convert one room of my house into storage for kleenex boxes, and another into a giant incinerator to dispose of used ones, and I'd need to take out a loan to pay the water bill for all the hand-washing, and to pay for skin grafts on my hands.)This article
talks about an interesting experimental approach. But since it's happening in China, I have no confidence the results will be trustworthy.