which covers all four types of flu Um, no. There are 4 categories of flu (influenzavirus A/B/C/D), but there are almost 200 possible unique HN strain combinat

which covers all four types of flu Um, no. There are 4 categories of flu (influenzavirus A/B/C/D), but there are almost 200 possible unique HN strain combinations of type A alone (not all of which affect humans). Maybe FI6 will direct us to a universal vaccine against all type A variants, but we're not nearly there yet.