I should resist replying to this pathetic dead cat, but anyway...
Terrorists commit acts of terror to cause shock, fear and ... terror So they pick things that are extremely violent, spectacular and most critically, UNEXPECTED. Little to be gained in spreading a virus that is already out and in the community. Hard to claim responsibility, people have already changed their behaviour in any case.
Can you imagine a terrorist spreading the virus in the UK? "That's ok, we don't care, it's already out, we are much better at treating it and we are all getting vaccinated anyway".
Complete wank.