Way #1: Burning the Virus
This section describes the final part of the mission. It is best to approach this part after killing the previous targets to make getting to the lab easier. Start in the building located in (M4,58) and go downstairs.
Head to the lab. Turn left by the guarded door. Turn of the power cords (M4,17) and knock out the scientist when a guard will be checking the reason for the blackout. Move the body to the chest take his suit and get rid of all of your weapons, as you will be searched.
Go back to the guarded door (M4,19) and go downstairs. Approach the guard (M4,39), knock him out and take his suit. Go downstairs via the passage nearby and approach the main control panel of the lab (M4,41).
Keep it low-key; do not let anyone recognize you. Read the safety protocol (M4,17) to find out how to get rid of the virus. Come back to the place with the scientist disguise and war it again.
Go past the guards (M4,53) and head to the room with protective clothing (M4,54). Use one of them and come back to the room with the virus (M4,42).
Approach the panel with the samples and use two of them on each other to cause a malfunction. Then, hack the computer. You will get an attention of the lab workers. Approach the control panel close to the virus (M4,42) and increase the temperature. You can leave the mission area now.
Way #2: Destroying the Virus Remotely
Go to the church (M4,28). By a confessional (M4,23) you will be able to overhear a conversation a peculiar confession. You will hear about an accident in the lab. Leave the area and go to the morgue (M4,25), which will be closed and guarded. Go to the cemetery where you will find a gravedigger.
Wait for an employee to finish the inspection. He will go in a more isolated place (M4,26) for a break. This is the right moment to knock him out and take his clothes. A woman will appear. Follow her to the morgue and hide in a coffin before the arrival of a priest.
Knock out the lab worker when the priest will leave her alone. Take her card and laptop key. Hide her body in the chest.
Go to the lab (M4,32). You will see a power box - turn it off and go hide yourself in a chest. Wait for a scientist to appear. Knock him out and take his clothes. Hide his body in the chest that you have just left.
Follow the path and, after leaving a tunnel, go upstairs to the roof. Sneak behind the scientist and approach the laptop (M4,40). Use the key and start the elimination of the virus.