A high fever lasting 4 days along with a cold, stomach discomfort, and mouth ulcers in a child can often be due to a viral infection, which is quite common and may affect different parts of the body at the same time. Some viral illnesses can cause fever, throat or nasal symptoms, mild stomach upset, and painful mouth ulcers, especially when the immune system is fighting the infection. However, persistent fever for several days should always be taken seriously because other infections like bacterial illnesses or dengue-like viral fevers, can sometimes present with similar symptoms. Keep your child well hydrated with water, ORS, and light foods, and avoid spicy or acidic items that may worsen mouth pain. Rest is very important for recovery. Since the fever has already lasted 4 days, it is important to get a doctor?s evaluation for proper examination and possibly basic blood tests to find the exact cause. Seek urgent medical care if there is worsening fever, refusal to eat or drink, severe abdominal pain, rash, or signs of dehydration.