Like all fish, wild salmon can harbour parasites in its raw form. Aside from cooking the fish, freezing it for at least 7 days should also kill the majority of parasites. In the UK there are several regulations relating to the freezing of salmon. In essence, eating previously frozen farmed salmon carries a low risk. I am using salmon that I've bought frozen then defrosted. To be sure you can also buy sashimi grade salmon, which is safe to eat raw. The act of curing the salmon with the salt and sugar will stop bacteria from growing, but only cooking the salmon will remove it completely. When you are preparing fish for curing it is sensible to make sure that all of your utensils and surfaces are hygienically clean. If you are in any doubt, or are in a vulnerable medical group, please seek advice.