Cause
In babies and small children, pneumonia acquired in an outpatient setting is often a mixed infection of bacteria and viruses. A bacterial one is often preceded by a viral infection of the upper respiratory tract. About a quarter of all pneumonia is of viral origin and the younger the patient, the more likely viruses have caused the pneumonia.
In 80% of the diseases of children between 2 months and 2 years of age, a viral cause is underlying. Respiratory Syncytial Virus (RSV), influenza and adenovirus are particularly common. Other viruses that can cause pneumonia include the following: Rhinovirus, enteroviruses, varicella-zoster virus (chickenpox), Epstein-Barr virus, various herpes viruses, the cytomegalovirus (CMV) and measles viruses.
The most important bacterial pathogens, which however only play a major role in advanced childhood, are Streptococcus pneumoniae, Mycoplasma pneumoniae and Chlamydia pneumoniae. The former poses a threat to health for all childhood age groups because it is very widespread. Of all the age groups of babies and infants, neonatal pneumonia must be distinguished and considered the most sensitive.
The child can develop pneumonia shortly after birth within the first three days of birth as part of a neonatal infection or only after several days. The time until the onset of the disease is related to the length of the cycle the pathogen has to go through. The classification of the transmission mechanism is based on the delivery.
The pathogens can be transmitted to the fetal lungs by aspiration (inhalation and ingestion) of infected amniotic fluid and by pathogens in the placental blood before birth. After birth, there is the possibility of infection directly during the act of delivery by pathogens in the woman’s birth canal, but also after delivery nosocomially by the mother or staff. Examples of pathogens transmitted in the mother’s abdomen are rubella, CMV, Treponema pallidum and Listeria monocytogenes.Perinatally (“at birth”), streptococci (group B), Escherichia coli, Staphylococcus aureus and Klebsielles are important species.
Furthermore, atypical pathogens or fungi can be the cause of pneumonia. With the current standards of the industrialized countries, however, this is very rarely the case and represents a medical rarity. If the child is not immunocompromised, an outbreak practically never occurs in a normal environment. Small-scale outbreaks of this kind only occur in countries where hygiene standards and medical care are extremely poor. Fungal species that outbreak in such areas are for example Histoplasma capsulatum and Coccidioides immitis.
