Chicken is a good source of protein, but raw chicken can also be a source of food-poisoning bugs. The one we tend to hear most about is Salmonella, but there’s another bug that often hangs out in the guts of chickens, called Campylobacter. It doesn’t seem to bother the chicken, but if we humans consume enough live Campylobacter it can cause unpleasant illness.
That’s why it’s important to make sure chicken is thoroughly cooked - so that the bugs are cooked too and can no longer cause a problem.
The safefood website offers advice on good hygiene and how to avoid cross-contamination, including the importance of not washing the bird under the tap before roasting it. "The practice of washing or rinsing poultry under the tap is likely to lead to increased risk of the spread of germs including Campylobacter in the kitchen, through splashes and droplets, given the levels which may be present on raw poultry," states a release on the website, which you can read in full here.