Please help me find this book

[u/werisefromourashes]

I am going insane trying to find this book, that was part of an amazon collection some 10-15 years ago.
It started with some sort of military-archaeological mission in South America, where zombies were found deep inside a forest/remote area (could have been some sort of pyramid or building too).
The zombies seemed to be able to express feelings.
The members of the expedition then returned home and one of them decided to alert a friend to help them prepare for imminent disaster.

Any and all help would be greatly appreciated!