The balloon represents the tuberculosis granuloma and the pencil represents risk factors such as smoking, stress, immune suppression and so on. A balloon and a sharp object. Kind of oversimplified, but it works to an extent. I know it isn’t very artistic but this is pretty much the most I can do without driving myself to insanity over my lack of artistic skill, but I hope you at least get a small chuckle at my expense. If you want to learn more you can always watch this video of tuberculosis found on blackboard, or a personal favorite of mine, this video that reviews a case of tuberculosis in a popular video game, Red Dead Redemption 2.