Addition and escalation (voire)

When you want to introduce an extreme possibility, use the conjunction voire (and even / if not). It connects two related ideas, escalating to a stronger, more intense version of the first.

The symptom is serious, and even unbearable.
Le symptôme est grave, voire insupportable.
The illness is very contagious, and even deadly.
La maladie est très contagieuse, voire mortelle.

You can use voire to connect adjectives, adverbs, and nouns to show a clear progression.

The lockdown is long, and even endless.
Le confinement est long, voire interminable.
The patient coughs often, and even all the time.
Le patient tousse souvent, voire tout le temps.
The doctor is looking for a treatment, and even a vaccine.
Le médecin cherche un traitement, voire un vaccin.