Varicella is caused by the varicella-zoster virus (VZV), which also causes shingles (herpes zoster). The virus typically affects children aged 2‒8 years.
Rotaviruses are the single most important cause of severe diarrhoeal illness in infants and young children worldwide. By the age of five years most children irrespective of socioeconomic setting will have been infected at least once. While infected, many children will be in need of medical attention due to extensive fluid loss.
Meningococcal disease is caused by Neisseria meningitidis, a bacterium with human carriers as the only reservoir. It is carried in the nose, where it can remain for long periods without producing symptoms.
Mumps is a viral infection first described by Hippocrates that in its classical form causes acute parotitis and, less frequently, orchitis, meningitis and pneumonia.
Despite good access to effective antibiotics, Streptococcus pneumoniae (pneumococci) is still a major cause of disease and death in both developing and developed countries. Pneumococci are the main cause of bacterial respiratory tract infections, such as pneumonia, middle ear infection, and sinusitis, in all age groups.
Poliovirus is highly contagious and infected individuals shed virus in the faeces and from oral secretions, thus the mode of transmission is person-to-person, both via the faecal-oral and the oral-oral routes.