Dengue Fever: Given the travel history to Costa Rica, Mexico, Turks and Caicos, and Guatemala, all of which are endemic for dengue fever, this diagnosis is highly plausible. Dengue fever is characterized by high fever, severe headache, pain behind the eyes, joint and muscle pain, rash, and mild bleeding.

Zika Virus: Similar to dengue, Zika virus is prevalent in the mentioned regions and can cause fever, chills, body aches, and sometimes a rash.
Chikungunya: This viral disease, also common in the traveled areas, leads to symptoms like fever, joint pain, and swelling, among others.
Influenza: Although not exclusive to these regions, influenza can cause similar symptoms and should be considered, especially during flu season.
Typhoid Fever: Given the travel to areas where typhoid fever is common, such as Guatemala and Mexico, this bacterial infection should be considered, especially if the patient has consumed contaminated food or water.

Malaria: Although less common in some of the mentioned areas, malaria is a critical diagnosis not to miss due to its high mortality rate if untreated. It's particularly concerning if the patient has been in rural areas or hasn't taken prophylaxis.
Yellow Fever: If the patient was in areas of Central America where yellow fever is endemic and didn't receive vaccination, this diagnosis could be critical.
Leptospirosis: This bacterial infection, which can be contracted through contaminated water, has a wide range of symptoms including fever, chills, and body aches, and can be severe if not treated promptly.

Hantavirus: More commonly associated with specific activities like hiking in rural areas of the Americas, hantavirus can cause severe symptoms including fever, body aches, and sometimes severe respiratory issues.
Rickettsial Diseases: Such as Rocky Mountain spotted fever, these diseases are transmitted by ticks and can cause fever, headache, and rash, among other symptoms.
Viral Hemorrhagic Fevers (VHFs): Although very rare and more commonly associated with specific outbreaks, VHFs like Ebola (less likely given the travel locations) or Lassa fever (not typically found in these regions) could present with severe symptoms including fever, chills, and body aches, and are critical to identify due to their high mortality rate.