[Acute fever in infants].

The body temperature is influenced among other things by time of day or age and exhibits a Gaussian inter-individual distribution. If measured orally, normal values vary between 35.6 degrees C and 38.2 degrees C. Temperature exceeding the 99th percentile (> 37.7 degrees C) can therefore be interpreted as fever. Nevertheless, an universally accepted definition of fever does not exist. Viral infection is the most frequent cause of acute fever in infants, even in the absence of a source. Bacterial infections are by far a rarer reason. Nevertheless, below the age of 3 years, acute fever is a ticklish issue because of the higher risk for rapidly evolving life-threatening invasive bacterial infections. Following introduction of vaccination against Haemophilus influenzae type b (Hib), Streptococcus pneumoniae has advanced to the most frequent cause of invasive bacterial infections in infants. Fever is rarely seen in newborns (age 1-28 days), but when present, it is more frequently serious. Around 12% of these newborns show an invasive bacterial infection. Therefore, a full workup for sepsis is strongly indicated. This includes cultures of blood,urine and cerebrospinal fluid plus a chest radiography. In addition, immediate start of an empirical intravenous antibiotic therapy and monitoring in a hospital setting are necessary. Apart from this exception, primary antibiotic therapy is rarely necessary in fever without a detectable focus and source. Also, routine prescription of antipyretics is not indicated. Though paracetamol may improve well-being and drinking behavior of infants, it does neither shorten the duration of fever duration, nor prevent febrile seizures.