This chapter provides an overview of some of the infectious diseases. Viral fevers are the most common cause of fevers seen in clinical practice and most of them are self-limiting, and do not require any specific therapy. A viral fever typically presents with a high grade fever at the onset, with the intensity of fever decreasing and the intervals between spikes increasing over the next few days. Infants less than 3 months with fever, child not able to take orally, suspected sepsis, dehydration, respiratory distress, altered sensorium, skin rashes or children with any other complicating factors need to be strictly monitored and hospitalized for further management. Certain viral infections require specific therapy. Typhoid fever presents with a rising fever in a step ladder pattern in the first week of illness and bacteremia. The child is usually not active in the inter-febrile period. In the second week of illness, rose spots may be seen on the trunk and abdomen. Hepatosplenomegaly may be noted. Isolating the organism from blood culture is the gold standard for diagnosis. Blood cultures are positive in a majority of the cases, depending on the timing of the test and prior usage of antibiotics. Antimicrobial therapy is essential in enteric fever to minimize complications. Children may be asymptomatic during the initial phase of malarial infection or may present with prodromal symptoms like mild fever, headache, nausea, vomiting, myalgia and fatigue. Classical presentation consists of paroxysms of fever with the child being well in the inter-febrile period. Typical clinical signs that are commonly seen are splenomegaly, with or without hepatomegaly and pallor. Chloroquine is the drug of choice for uncomplicated vivax malaria in all regions. Symptomatic dengue virus infections can present with a range of clinical manifestations ranging from a mild illness to a life-threatening illness. Most patients of dengue present as a mild self-limiting mild illness and recover, and few develop severe disease. The diagnosis of dengue is mainly clinical. Serological tests may be used to confirm the diagnosis. Early empiric therapy should be instituted in suspected cases of rocky mountain spotted fever (RMSF) depending on the clinical features and the epidemiology.