[Title Sci-fi novel] Group stranded on alien jungle planet, monitored by insect-like cameras, releases virus to escape at the end (80th or before)

What is that book? I read this science fiction novel (short or long) in the 1990s, but I think it was published in the 1980s or possibly earlier.
Here’s what I remember:

A small group of men and women is stranded on a wild, jungle-like planet that is not Earth.
They slowly realize that flying insects around them are actually small surveillance devices — cameras or monitors — used by some invisible or advanced alien species.
The planet is essentially a lab or experiment, and the group is being watched, tested, and manipulated.
The story ends with a very dark choice: the only way the humans can escape is to release a deadly virus that causes a genocide of the alien race keeping them prisoner.

Thanks for any help!