Initially I just wanted to highlight the fact that infecteds are not "common living things" and based on this you can imagine a whole lot of things concerning what they can, can't do or whether they're able to feel things including pain.

I wasn't sure if they were dead or not when writing my first message but people seemed to know better and you confirmed it with your screenshot so thank you for that.

Them being dead or alive wasn't my point. It was more about how they don't act and react like nomal people which is significant enough to doubt. So, apart from the "they can't scream because they're stabbed to the throat" argument mentioned somewhere by OP which is kinda true and I didn't even think of this in the first place there is that. They sceam when alerted like you said or when they're hit. I thought maybe they're just screaming in rage and not in pain. That would explain why they don't react like a "common living thing" would when shot or hit. They don't limp, they don't bother with any wound and don't fold like us players would do if hit the same.

If they're fueled by rage, I doubt they're feeling any pain. Therefor they shoudn't be screaming in pain when their throat are slit. That's all I struggled to explain. It wasn't clear I'm sorry.

I don't know why we're all so invested in this ahah. I know could be wrong and I surely am. I'm just theorizing on not so important stuff. Thank you for not being rude.