What can cause a quick and intense fever that lasts only few hours?

Several conditions can cause a quick and intense fever that lasts only a few hours. Here are some possible causes:

1. Viral Infections: Certain viral infections, such as influenza (the flu), can cause a sudden spike in body temperature, resulting in a high fever. These fevers may come and go quickly, lasting anywhere from a few hours to a day or two.

2. Bacterial Infections: Some bacterial infections, like certain types of urinary tract infections or pneumonia, can also cause a rapid onset of fever. These fevers may be accompanied by chills, muscle aches, and other symptoms.

3. Drug Reactions: Certain medications or vaccinations can trigger a fever as a side effect. These fevers usually develop within a few hours of taking the medication or getting the vaccine and typically subside within a short period.

4. Allergic Reactions: Severe allergic reactions, known as anaphylaxis, can cause a sudden and intense fever along with other symptoms such as rash, swelling, difficulty breathing, and dizziness.

5. Heatstroke: Prolonged exposure to extreme heat or strenuous physical activity in hot environments can lead to heatstroke, characterized by a dangerously high body temperature. This condition requires immediate medical attention.

6. Febrile Seizures: In children, a high fever can sometimes trigger a febrile seizure, which is a temporary loss of consciousness accompanied by involuntary muscle contractions. These seizures usually last a few minutes and resolve on their own.

If you or someone you know experiences a sudden high fever that lasts only a few hours, it's important to monitor the situation closely. While some causes may be self-limiting and resolve without treatment, others may require medical attention. If you have concerns or if the fever is accompanied by severe symptoms or lasts longer than a few hours, consult a healthcare professional.