NITA BHALLA  KENYAN sex worker Silvia does not much like the large, oblong-shaped blue pill she takes with her porridge every morning. While the daily tablets of pre-exposure prophylaxis (PrEP) drastically cut her risk of getting HIV, they bring with it stigma and even violence due to the common misconception that the drug is taken by people who already have the virus. "I was beaten up by a client who found the pills in my handbag. He thought I had AIDS and accused me of giving it to him and hit me on the head with bar stool. I ended…