Do you know how ultraviolet light kills bacteria?

At the beginning of 2020, a sudden new type of coronavirus (COVID-19)swept across the country at an unprecedented speed, causing panic. People rushed to buy masks, disinfectants, alcohol, Shuanghuanglian, and of course ultraviolet lamps. So What is deep ultraviolet? What is the principle of its sterilization?
How long does UVC-LED need to be irradiated to sterilize?
Short-wave ultraviolet radiation with wavelength of 240-280 nm is also called deep ultraviolet radiation(UVC). It can destroy the DNA or RNA molecular structure of bacteria,make them lose reproductive ability and achieve bactericidal purposes. At present, no antibody has been found in the bactericidal band of bacteria and viruses. According to a number of experimental comparisons and authoritative test reports, the bactericidal rate can reach 99.99%.
UVC-LED(Deep Ultraviolet LED) technology has the advantages of non-toxic, mercury-free, pollution-free, effective power, ozone-free generation, small size, portable and so on. ROHS certifcation does not contain toxic and harmful substances, and its service life is up to 20000+hours.
UVC-LED is ready to kill, depending on the difficulty of killing different bacteria and viruses. the time is different. Escherichia coli. influenza virus. dysentery. typhoid fever, hepatitis B virus and other common viruses can be killed in 10 seconds. We reserve 2-3 minutes for each product according to the experimental data to kill more invisible unknown bacteria and viruses.