The Medical Pamphlet is a CDC leaflet inside the truck blocking your path outside the museum. Push an object against the truck to climb over, then look back: the opening is on the right side and the pamphlet is to its left.
The pamphlet describes Cordyceps as a parasitic fungus that once only hit insects until a strain began infecting people. It lists two ways to catch it: spores or bodily fluids, usually from a bite. The parasite reaches the brain in a day or two, there is no vaccine, and a quick blood or imaging test detects it within minutes.
It is the most complete explanation of how the infection works that you find early on, covering the spores you have just walked through and the bites Joel keeps warning Ellie about.
Davidson's Firefly Pendant
Davidson's Firefly pendant lies underwater in a stone rotunda in The Capitol Building section of The Outskirts. It belonged to Melinda Davidson and is easy to swim past.
Evacuation Leaflet
The Evacuation Leaflet is an old FEDRA warning on the right-hand pavement in downtown Boston. Once you climb the collapsed street and Tess and Ellie start talking about the bombing, look by the base of a traffic light a car has hit.
Field Ops Log
The Field Ops Log is a soldier's patrol record inside the Goldstone Building, the tilted skyscraper downtown. Climb the stairwell toward the fifth floor; it lies beside the second dead soldier, along with a couple of 9mm rounds.
Firefly Map
The Firefly Map is a note on a dead Firefly in the subway station downtown, on the stairs between the two escalators. It is the body to the right of the one carrying a Molotov cocktail.