Chandra Wickramasinghe is well-known as a supporter of Fred Hoyle's theories about panspermia, which have not yet won general acceptance in the scientific community. Thus, this news item is not likely to fill too many scientists with dread about the possibility of a looming plague. None the less, the Universe is a big place, and while contamination by alien life is unlikely to be a common thing, it's still a real possibility, so some degree of caution is reasonable.