Great question and thats one of the most important things I take into account when planning my work! The answer is yes it could be dangerous but we used lots of equipment to make it safe! So we use microbiological hoods which prevent the air from coming out so the virus is contained in one place. We wear labcoats and gloves to protect ourselves, we are all vaccinated to stop us from getting accidently infected and most importantly we cook all our waste that our experiments generate so the virus is killed before the waste is taken away. There are lots of government agencies that keep an eye on us scientists so there is no risk to the public or ourselves from our work!!