Thank you for your query on Healthcare Magic.
Low WBC count is associated with viral fever
and also is seen in Typhoid fever
Vomitings may be due to associated gastritis which is commonly seen in viral fevers and gut infections.
Because of vomitinds there may be a tear in the lower end of esophagus
which causes bleeding into stomach and this blood turns into coffee ground color because of the action of gastric acid
present in the stomach.
Or some times erosive gastritis leads to bleeding into stomach.
Black to brown color vomiting is suggestive of some amount of bleeding into stomach.
It can be managed by keeping the child nil by mouth, on IV proton pump
inhibitor, IV anti emetic, and IV fluids.
Infection to be treated accordingly with antibiotics if required.
Discuss your concerns with the treating doctor.
Hope I have answered your query.