Hep C is transmitted only by blood, and is rarely transmitted sexually. When it is, it's usually by anal sex.
Even if a woman is having her period, that blood would still have to get into the giver's blood stream. I'd probably avoid oral sex on a woman if she has hep C and has her period, but that's probably being very, very cautious.
Hep A (in case that's next) is transmitted by fecal matter, and is often transmitted by contaminated foods. It can be transmitted in day care centers, etc., and can be transmitted by oral-anal contact.
There is a vaccine for hep A and hep B. If people are concerned, they can get vaccinated.
so only the blood can detect the virus. Not in vaginal secretion and semen?