Anscombe-view-of-causality is an objection to the notion of causal necessity and universality that Humean-theory-of-causation insists on.
Anscombe’s example shows that while we can say “contact with a carrier causes diseases”, this is not always true, and so we cannot say that the cause necessarily brings about the effect. Therefore, the concept of causation does not depend on necessity.
Humean response: appealing to the notion of Full cause = what we have identified as the cause is only a partial factor in a larger conjunction. If the full cause were known, it would always and necessarily produce the effect. This example of contact causing disease is a loose causation.
Anscombe’s argument against the notion of Full Cause = our practice of talking about causes does not presuppose that we know, or even that there is, such a necessitating set of conditions. even if there is a full necessitating condition, our ordinary use of causal concepts doesn’t rely on it — so necessity is not what grounds the concept of causation.
A related point of Anscombe is that causal generalizations do not have the universality that Humean theory posits. In order to achieve true generalizations, we would need to exclude the circumstances in which A would not cause B.