What's This Pink Thing?
Helminth Cyst
So, one day you come online and you see a pink cyst upon your neck. "WHAT THE HELL IS THIS?!" you wonder. Well, my friend - that is a Helminth Cyst. We can all give our thanks to the Warframe Nidus for this. Nidus is an infested Warframe that infects others. You can also become sick from Warframes that have become sick from Nidus. Don't fret! There are two ways to cure this.
Temporary Cure
There is a temporary cure, however, the Howl of the Kubrow quest is a prerequisite. Which, you can obtain from completing the Mercury Junction on Venus. The cyst will continue to grow in size until 7 days have passed, at which point it will be fully matured, as seen by the small tendrils sprouting from its surface. The player may drain the mature cyst into an available Kubrow egg which will allow you to breed a new type of Companion, the Helminth Charger, from the Orbiter's Incubator Segment; a new cyst will appear 24 hours after draining it.
Permanent Cure
There is a permanent cure to the Helminth Virus. Located at the back left-hand side of your ship there is a door surrounded by infested parasites. The door will only open once your Helminth Cyst has fully matured (7 days). Inside of the Helminth Infirmary, there is a chair, once you sit inside the chair your Warframe will be permanently cured. Your Warframe will no longer be able to contract the Helminth Virus regardless of being in missions with other players who may be sick. The door will always open for Nidus regardless of being sick or not, and having Nidus sit in the chair will make him be able to spread diseases.