Abandon All Hope...
I know. It seems a little extreme, but the consequences are reason enough. These foreign contagions can spread through a ship like fire. It can spread across a planet just as fast. A plague ship crashing on a planet is cause for concern, but many ships come with automated landing protocols. These ships gently glide to the ground, land, and sit just waiting for someone to step inside. If those who do are allowed to leave, it could wipe out the population just because the planet happened to be in the way. The consequences alone are reason to avoid these ships, but for some, it isn't that simple. Those ships could have technology, tactical information, resources, and who knows what inside. Take the right precautions, and this wealth could be yours.
Crime and Opportunity
Criminals exist in the void, and they are never opposed to stepping into a plague ship. They strip everything of value and leave, after thoroughly decontaminating it, of course. It's highly profitable, and it even earns some goodwill among local populations. These scavengers are known for delivering transmissions to the family of those who died. The Sea of Names, a well-known pirate vessel, is notorious for this. This practice is exactly how it got its name. Some groups are known to stash illicit goods and smuggle them on marked plague ships. People know about it, but the possible contamination is well beyond their pay grade. The only exception is when too many plague ships appear in a short period of time, making the illegal operations obvious.
This organization, referred to as Caduceus by humans, is a multi-species initiative dedicated to clearing plague ships. The name doesn't truly refer to the organization, but instead refers to a human vessel within in. The SVN Caduceus is a medical cruiser created in Caydie's Cradle on Safeharbor. The vessel is predominantly crewed by humans. It's the first ever human vessel with more than one species on its crew. The organization imposes strict rules of isolation. Every member is a member for life, and will never see the surface of a planet again. They do this because of the changes made to their physiology. Each member has a slew of vaccines pumped into their system. Their immune system is second to none. This allows them to work together without fear, but also makes them likely to be carriers of the contagions they encounter.