I remember being obsessed with this game when I was like 9 and discovering NG. Then I discovered it again, played it again, and I'm...still obsessed tbh. I definitely think the sequel's better than this, but it's also quite laggy, so if you'd like to have a fun, short experience with less lag or difficulty, simply play this one...they're both SICK!
Side note: To those who say "Uhm antibiotics don't kill viruses this game is factually inaccurate" that information would be a lot more important to tell patients, not on a Flash video game from the 2000s.