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Disclaimer: I do not own Harry Potter or any of the characters portrayed in that series. Slightly AU, but that difference will be mentioned. Hermione seems too progressive to ever change her last name completely, and Ron would be willing enough to accommodate her.
Fact and Logic
All things have a cause and an effect. There are facts, pieces of information, and there is logic, which helps us interpret what those facts mean.
Fact: On October 31st, 2016, all British purebloods, save roughly a hundred, showed signs of the bubonic or "black" plague; all of those who showed signs of the bubonic plague were dead within forty-eight hours.
Fact: This strain of disease was one of a number of recently emerging magic-resistant diseases.
Fact: On November 12th, 2016, Hermione Jane Granger-Weasley discovered a strain of Muggle anti biotic which destroyed diseases' immunity to magic, only a little under two weeks too late.
Fact: No members of formerly "Dark" pureblood families were invited to Minister Ronald Granger-Weasley's parties; the parties were attempts to reach out to and get a better feel for many of the neutral and "Light" pureblood families. Homemade butterbeer was served at all of the parties, often pressed upon the guests to "try just one sip".
Fact: Hermione Granger was captured by Death Eaters seven months before the end of the Second Riddle War, as it is now called in the Hogwarts history curriculum. When she was recovered, it was unclear if she would every be able to be around other humans without panic attacks and seizures.
Fact: Harry Potter, Ginevra Weasley, and their three children often visit the Granger-Weasleys over the summer; they find Hermione's homemade butterbeer delectable.
Fact: Hermione Granger is now the leading expert on hereditary diseases in both the magical and Muggle worlds, as well as the expert on magic-immune diseases. Her Muggle thesis was on the black plague.
Logic: Among the pureblood who died were many children and grandchildren of Death Eaters…