Whenever you go in a place where anacondas live, just always bring a gun, so if they going to attack you, just shot them til they died.
I doubt that they attack many people mainly because most people have no reason to hang around where anacondas live. Also, they assess potential prey visually, can it or can it not be safely swallowed. It isn´t risk free for the snake, once it start swallowing there may be no way back, legs, horns etc on the prey. They don´t just attack anything that moves. A standing human adult would probably look like an unusual prey to a crawling anaconda and certainly rather big. I´m not sure they´d be very interested. What they´re interested in is things they are familiar with and have hunted successfully forever. I doubt that humans are high on that list.
