SOLVED. Book about virus epidemic [s]

[Veronica]

I read this book in 1999/2000 but the book could have been older than that. It was set in modern times and was about a virus outbreak.

The symptoms of the outbreak included blood leaking from the eyes. In one description of an infected person, it felt like they were lying on grains of sand but it was a rash that had appeared on their body.

There is also a pair of twins girls in the story, I don't remember their age but I think they were pre-teen/teenagers, definitely not adults. They were traveling for some reason.

I remember part of the ending so I'll put in under spoilers.

(view spoiler)[ It's revealed the twins were conceived with either in vitro fertilization or surrogacy. I'm not sure if their parents were their biological parents or not. The doctor or medical corporation was conducting genetic experiments. The twins had some sort of mutation and it turns out they are the cause of the outbreak. (hide spoiler)]

[Kokomomomo]

Maybe Carriers?

[Veronica]

After reading the reviews with spoilers I'm certain that's the book. Thank you so much.