Infection
Start with the "Immune" category. It lowers the overall response of the patient and can make it easier for you to kill him later. Use the "Recovery" feat "Nosocomephobia" to keep your patient from going to the doctor. You can degrade his health a lot more. Do not start with diseases first because the patient will go to the doctor. Instead, work on everything else and unlock "Risk Factors". Depending on your level, some may already be available. If not, the "Over 60" is recommended, as well others that will unlock more complicated diseases later. After most of your patient's categories will begin to decrease slowly, get about 25 disease points. Then, go to the disease. Begin by spreading them evenly and attack as many areas as possible. Try to get all categories lowered and reach zero for the patient to die. If you concentrate on one category for too long, the patient will go to the emergency room and the cure will be ready faster. Check which of the seven categories have the lower health percentage then invest in a few more traits there. This will increase the rate of decay of that category; and it will eventually hit zero. At this point, the patient will be taken to the ER and recovery will be extremely fast. At this point, invest in the diseases strongly and use the nurse strikes to lower all the categories slightly faster. Invest in the lower ones again do bring down as many as possible.
Recovery
If your patient goes to the doctor, use the "Bad Doctors" feat to lower the research rate. After getting more disease points, have the nurses go on strike. Save at least one strike for when the patient goes to the Emergency Room.