Influenza infections occur commonly, have a well-defined seasonality, and most infections are mild.

Recent pandemic with H1N1 strain caused widespread panic. It highlighted the potential for worldwide spread of new strains.

Most of the cases of influenza in children are managed on an ambulatory basis. Of the children needing hospitalization, ˜15% need ICU care.

It has been hypothesized that cytokine storm plays an important and essential role in causing significant tissue injury and mortality following influenza virus infection.

Pneumonia associated with influenza virus infections may result from primary viral infection, bacterial superinfection, or combined bacterial-viral infection.

In severe cases, multiple organ systems are involved as manifested by focal and diffuse myocarditis, mediastinal lymph node enlargement and necrosis, and cerebral edema.

In addition to the supportive care required for management of critically ill children with influenza, specific antiviral therapy is indicated. The antiviral drugs include M2 protein inhibitors (amantadine and rimantadine) and neuraminidase (NA) inhibitors (oseltamivir and zanamivir).

Recent studies have reported a poorer prognosis in children with underlying chronic diseases.

HIV infection has become an important contributor to childhood morbidity and mortality, especially in many developing countries.

Children with HIV infection may need admission to PICUs because of respiratory infections and respiratory failure, septic shock, and central nervous system (CNS) disorders.

Severe complications of therapy may also become indications for admission into the PICU.

The PICU staff should be aware of postexposure prophylaxis.

Measles, a vaccine-preventable infection, is an important cause of death among young children.

The conditions associated with measles that may require intensive care include pneumonia, laryngotracheobronchitis, and CNS infections.

Vitamin A may be helpful in reducing the morbidity and mortality due to measles.

No proven antiviral drugs for measles are available.

Nonpolio enteroviruses are responsible for a variety of illnesses.

Some of the respiratory, myocardial, and CNS infections may be severe enough to require intensive care.