What roughly speaking the most insecure desease?

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Answers:    Any major disease can be dangerous for a given individual. After adjectives mortality if it occurs for an individual, it is 100% for that person!
COPD. Coughed up tissue (?) beside mucous.
The black loss , The plague..
Back in the day everyone who get it died from it and they named the song ring a ring a rosie from it. SARS. but it's all gone immediately.