Acutely ill infant


  • Signs and symptoms are often difficult to interpret in infants, so a complete examination must always be conducted. An infant may present with only a few signs even when seriously ill.
  • The younger the infant, the more likely it is that the illness is serious and will require hospitalization. In practice, 3 months may be considered as the cut off point; particular vigilance should be exercised if the infant is less than 1 month old.
    • Listen to the parents. A detailed history will guide the doctor more quickly towards the right diagnosis, and unnecessary investigations need not be carried out.
    • An afebrile infant with good muscle tone, who feeds well and shows satisfactory growth is rarely seriously ill.
    • If the general condition of the infant is reduced, make an emergency referral for further care in a hospital.

Clinical assessment

  • Make a quick general assessment with the emphasis on visual inspection.
    • Fever
    • Breathing (fast or laboured?)
    • Abnormal skin colour or temperature (pale, bluish, yellow, cold peripheries?)
    • Is the infant whining or sensitive to handling, stiffening his/her muscles, listless?
    • Feeding, weight gain, vomiting, normal stools?
  • A complete physical examination must always be carried out regardless of the reason for seeking medical help.
    • General condition, irritability, muscle tone, skin colour and temperature
    • State of the fontanelle
    • Mouth, pharynx and ears
    • Heart and lung auscultation and femoral pulses
    • Palpation of the abdomen, size of the liver, testicles and possible hernias

Initial treatment

  • If you evaluate the infant to be in poor general condition, treat immediately (top priority).
    • Assess the need of supplemental oxygen.
    • Intravenous fluid replacement (e.g. Ringer's solution) 20 ml/kg over 15 minutes. Continue with the fluid therapy until the blood circulation is stable.
    • Blood cultures through the infusion cannula
    • Rapid testing of blood glucose concentration. If it is low, give 10% glucose solution (G10) intravenously 2 ml/kg over 3–4 minutes.
    • Consider starting antimicrobial treatment if the distance to a hospital is long.

Fever (> 38.0°C)

  • Fever and a dislike of being handled are often indicative of a serious infection.
  • Febrile infants younger than 3 months need always to be assessed urgently by a doctor. Febrile infants younger than 1 month should be sent directly to a hospital because they have a great risk of developing a generalized bacterial infection (table T1).
  • See also (A child with fever).

Table 1. The most common causative organisms of systemic infection in febrile infants
Microbe Infectious disease
Bacteria Pyelonephritis (E. coli)
  • Neonatal infection of group B streptococcus (GBS)
  • Pneumococci in older infants and young children
  • Staphylococci particularly in those admitted to hos
  • Meningococci is more rare; remember to check the infant for petechiae
  1. Influenza (influenza virus A and B)
  2. Adenovirus infection
  3. Exanthema subitum (also known as sixth disease and roseola) and other herpesviruses (HHV6/HHV7)
  4. Hand, foot and mouth disease
  5. Herpes simplex (HSV) encephalitis

Respiratory distress

  • A respiratory tract infection in young infants is often associated with respiratory distress which, if present, is always an indication for hospitalisation. See also (Wheezing in children).
  • Bronchiolitis in infancy is a respiratory tract infection usually caused by the respiratory syncytial virus (RSV). Widespread epidemics are fairly common.
  • The main signs are tachypnoea, overdistension of the chest due to air trapping and intercostal and sternal retractions. Expiratory wheezing and inspiratory crepitations may be present. Apnoeic episodes may occur.
  • The nose is the preferred primary route of breathing for an infant. Nasopharyngeal secretions and stuffiness leading to feeding difficulties may require repeated nasopharyngeal suctioning in a hospital even if the infant does not have bronchiolitis.
  • Pneumonia does not always present with breathing difficulties. More important than trying to distinguish between an upper and lower respiratory tract infection is to identify and treat respiratory distress.
  • CRP and a chest x-ray will help to decide whether or not an antimicrobial drug is needed.
  • Heart failure is a rare cause of respiratory distress.


  • A respiratory tract infection is often associated with a cough, but a cough is a rare symptom in a very young infant.
  • Ask if other family members have a cough.
  • A suspicion of whooping cough (Whooping cough) in an infant is sufficient to warrant hospitalisation and starting treatment with a macrolide. Vaccination does not offer total protection against whooping cough, and whooping cough should be particularly suspected in an unvaccinated afebrile child who presents with heavy coughing.

Central nervous system symptoms

  • A seizure requires immediate medical treatment, primarily with rectal diazepam (0.5 mg/kg) or buccal midazolam (dose for the buccal preparation 0.25 mg/kg) (Treatment of acute seizures in children). The airway must be kept open and adequate oxygenation ensured.
    • In association with the first seizure, the child should always be examined by a paediatric neurologist or a paediatrician in order to investigate the cause of the seizure and to plan the prevention of further seizures. Typical febrile convulsions (Febrile convulsions) of short duration are the only exception. These occur in children over 6 months of age.
  • Fever and CNS symptoms in a small infant always require emergency investigations in a hospital in order to exclude a CNS infection.
  • Nuchal rigidity is a rare sign in meningitis (Meningitis in children), but the front fontanelle may be bulging.
  • Hypoglycaemia, hypocalcaemia and hyponatraemia may cause neurological symptoms. Using point-of-care testing, the blood glucose level should be determined from all small infants with non-specific symptoms brought to an emergency department.
  • Medical data are usually available relating to possible perinatal and postnatal causes, such as cerebral haemorrhage or asphyxia related to prematurity.
  • Developmental disorders of the brain, metabolic disturbances and degenerative illnesses are possible, but rare, causes of cerebral symptoms.
  • Onset of epilepsy is rare during infancy, but infantile spasms and other similar conditions are an indication to refer the infant urgently to hospital as early treatment has an influence on the outcome. Infantile spasms typically consist of repeated episodes of the body stiffening into flexion or extension for 0.5–1 seconds.
  • In many cases of shaken baby syndrome there are no externally visible signs. The possibility of child abuse should be borne in mind (Identification of child physical abuse). The slightest suspicion of abuse is an indication for urgent referral to specialist medical care.

Heart failure

  • Signs and symptoms:
    • dyspnoea
    • sweating and tiring when feeding
    • poor weight gain (due to poor feeding and/or an increased need for calories)
    • poor colour (if the infant is particularly pale, anaemia should be excluded as a possible cause of the heart failure)
    • hepatomegaly
    • cardiac murmur (not present in all cardiovascular conditions)
    • weak femoral pulses (coarctation)
    • tachycardia (if significant, i.e. over 200/min, heart failure may be caused by SVT).
  • No symptoms may emerge until after the first few weeks of life, when the transition from foetal circulation is completed, even in cases of significant anomaly of the heart and/or circulation.
  • If heart failure is suspected, the following investigations are indicated: oxygen saturation (separately from each limb), chest x-ray (cardiomegaly, pulmonary vascular congestion), ECG (arrhythmias, conduction disturbances), blood pressure from each limb (normally higher in the legs than in the arms) and blood counts (possible anaemia).

Acute abdomen

  • An infant is not able to indicate that he/she has abdominal pain, and an assessment of the infant’s abdomen and urogenital area must always be included in the routine examination (Acute abdominal symptoms in children).
  • Vomiting
    • Vomiting is the most common manifestation of an acute abdomen, but many conditions of non-intestinal origin may also induce vomiting in children.
    • Projectile vomiting at the age of approximately 1 month is suggestive of pyloric stenosis.
    • Greenish (bile stained) vomit is always abnormal and requires further investigations.
  • Bleeding from the anus
    • Exclusion of an intussusception requires investigations in a hospital. The condition is not common in children younger than 6 months.
    • In young infants, blood mixed in with the stool is usually of no importance and originates from an anal fissure, rash or rectal inflammation that will resolve spontaneously. In rare cases, the underlying cause is cow’s milk allergy or bacterial infection.
  • If gastroenteritis is the cause of the vomiting it also causes diarrhoea. Gastroenteritis is not common in very young babies.
  • Appendicitis does not occur in young infants.
  • Rare intestinal developmental disorders include malrotation and Hirschsprung’s disease which may manifest themselves as an acute abdomen.
  • Inguinal hernias in children younger than six months become easily strangulated. The main symptom of a strangulated hernia is pain. If the condition is prolonged it will lead to an acute abdomen. The first aid consists of manual reduction of the hernia, and the child should be sent urgently to hospital for surgical management.
  • A painful and red testis is an indication for an urgent referral to hospital for surgical management.
  • See also (Acute abdominal symptoms in children).


  • Most cases of neonatal jaundice are due to a prolongation (> 1–2 weeks after birth) of physiological jaundice and/or breast milk jaundice of an unknown aetiology (Jaundice in the newborn). Breast milk jaundice does not require treatment, but the diagnosis may be confirmed by switching over to an infant feeding formula for 24–48 hours.
  • Measures should be taken without delay to exclude haemolysis which requires immediate treatment (blood picture and reticulocytes) and infection. Prolonged jaundice is often associated with a urinary tract infection.
  • In addition to total blood bilirubin concentration, the conjugated bilirubin concentration is also determined. The result is abnormal if the proportion of conjugated bilirubin is 20% or more.
  • Many rare diseases may cause the level of conjugated bilirubin to rise, but it is most important that an obstruction or atresia of the biliary ducts is diagnosed. Pale coloured stools and dark urine are suggestive of an obstruction of the biliary ducts. The child’s good general condition should not delay a referral to specialist medical care.
  • The investigations of jaundice in older infants are carried out in the same way as in older children and adults (different types of hepatitis, etc.). See (The icteric patient).

Copyright © 2023 Duodecim Medical Publications Limited.