Viral upper respiratory infection: Many viral upper respiratory infections, such as the common cold or flu, have an incubation period that can range from a few days to 2 weeks, making this a plausible cause for symptoms appearing at this timeframe.

Allergic reactions: Allergic reactions to new substances (e.g., foods, medications, environmental allergens) can sometimes have a delayed onset, potentially aligning with a 2-week timeline.
Bacterial infections: Certain bacterial infections might have an incubation period of around 2 weeks, though this can vary widely depending on the specific bacteria and the individual's immune response.
Medication side effects: Starting a new medication can lead to side effects that may not be immediately apparent, sometimes taking up to 2 weeks to become noticeable.

Meningitis: Although less common and typically presenting more acutely, some forms of meningitis can have a slower onset, making it crucial not to miss this potentially life-threatening condition.
Encephalitis: Similar to meningitis, encephalitis is a serious condition that might not always present with immediate severe symptoms, emphasizing the need for careful consideration.
Lyme disease: If the individual has been exposed to ticks, Lyme disease could be a consideration, as its symptoms can sometimes be delayed.

Toxoplasmosis: In immunocompetent individuals, toxoplasmosis might present with mild or no symptoms, but in rare cases, it could lead to more significant health issues, especially if the individual is immunocompromised.
Brucellosis: This zoonotic infection has a variable incubation period and could potentially present around 2 weeks after exposure, though it is relatively rare in many parts of the world.
Leptospirosis: Another zoonotic infection with a range of incubation periods, leptospirosis is less common but can be serious, making it a rare but important consideration in the right context.