You can keep the paragraph in question entirely in the present tense, but it wasn't entirely in the present tense to begin with. (Note the word gave, which is past tense.)Original:
Jane, the main character, is a young soldier. While she is on a mission with other soldiers, her unit is exposed to the virus and everybody except her is killed. She recovers from her injuries sooner than expected. The virus gave her an ability to heal herself from any kind of injury. For this the reason is the army trying to hunt her down and create nearly immortal troops. In the end she manages to escape and she starts new life.
Suggested rewrite:
Jane, the main character, is a young soldier. While she is on a mission with other soldiers, her unit is exposed to the virus and everybody except her is killed. She recovers from her injuries sooner than expected. Exposure to the virus gives her the ability to heal herself from any kind of injury. That is the reason is the army tries to hunt her down and create nearly immortal troops. In the end she manages to escape and she starts a new life.
Note: It should be a new life. (I missed that the first time.)
What do you think?