It would be much easier to identity an infected individual for quarantine if a virus had a steep fatality rate, the transmission would be much slower too since dead people don't travel.
Viruses tend not to work like that because to effectively spread via respiratory droplets and aerosols they require a high viral load in the respiratory system. This generally causes symptoms.
I’m sure it’s not completely impossible, but neither is a massive radiation burst from a nearby supernova.
Worst case would be a highly lethal, airborne virus with a long delay between infection and death.