Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
Encephalitis and meningitis aren’t very common, but they can be extremely serious. They may cause swelling of the brain, which can be fatal. That’s why it’s important to know the symptoms of these diseases. Both encephalitis and meningitis typically cause a severe headache and a fever. Meningitis also causes a stiff neck. Both require emergency medical treatment.


Question: Fatal swelling of what organ can result from both encephalitis and meningitis, which typically cause a severe headache and a fever?
brain
Brain.