yes, I look already, but it does not change the stamina after having the virus
Are you wanting it to behave like infection that applies debuff if left untreated and the condition worsens or do you want it to apply a debuff automatically as soon as it is applied, like the fatigue debuff you treat with vitamins?
For hungry, I was looking at this section which is probably what you are looking for:
<effect_group>
<triggered_effect trigger="onSelfBuffStart" action="ModifyCVar" cvar="$buffStatusHungryBlockage" operation="set" value="100"/>
<triggered_effect trigger="onSelfBuffStart" action="ModifyCVar" cvar="$buffStatusHungryBlockage" operation="add" value="@$PlayerLevelBonus"/>
<triggered_effect trigger="onSelfBuffStart" action="ModifyCVar" cvar="$buffStatusHungryBlockage" operation="multiply" value=".133"/>
<passive_effect name="StaminaMaxBlockage" operation="base_add" value="@$buffStatusHungryBlockage"/>
</effect_group>
So in this case, there is a variable (cvar = buffStatusHungryBlockage) that is calculated and then applied to the passive effect StaminaMaxBlockage. So if you were to do this same route, you would need to generate a new variable (for example buffStatusRabiesBlockage). In the example above, say the person has a level bonus of 20 for stamina. If they become hungry, the blockage value would be 15.96 (100+20)*0.133. This is then added to StaminaMaxBlockage via the last line.
You might be able to get away and use the same variable buffStatusHungryBlockage in your virus calculations. However, since your goal is to set the max at 100 stamina with the virus, you would just add the @$PlayerLevelBonus to the Blockage variable which would limit it to no greater than starting stamina.