RS-virus is short for respiratory syncytial virus which, in the winter months, is a common cause of acute bronchitis in small children. It typically infects children under the age of two, particularly those aged less than six months. However, the disease is rarely life-threatening and most children recover fully without any permanent problems.

RS-virus is usually transmitted from one person to another by direct contact. While an adult or older child may merely have the symptoms of a common cold, younger children and babies may develop severe exhaustion and admission to hospital may be necessary.

In small children, the disease usually begins with a runny nose and sneezing. The temperature then rises to about 38-39°C and the child starts coughing and has problems breathing. Symptoms usually develop within a few hours, but the most critical period normally comes two to three days after coughing starts.

The smaller airways in the lungs are then affected and breathing may become even more difficult and painful. This can cause the child to hyperventilate (breathe rapidly). Whistling sounds from the chest, a pale complexion and bluish discolouration around the mouth and under the fingernails are all possible signs that the child's condition has become more serious. Children under the age of six months will have trouble breastfeeding and their sleep will be affected by breathing difficulties.

In complicated cases - although these are rare - it might become almost impossible for the child to breathe. The problematic breathing combined with a high temperature may also cause the child to lose fluids which they don't replace. Symptoms can include:
drowsiness
cold, dry, pale skin
sunken eyes
a fast pulse
sunken fontanelles (the soft spot on the top of the head in children under the age of one).

By age 2, most children will have been infected with RSV. Children who attend child-care centers or who have siblings who attend school are at a higher risk of infection. So are infants who are exposed to high levels of air pollution or cigarette smoke.

Susceptibility also is greater during the peak RSV season, which typically begins in the fall and ends in the spring.

People at increased risk of severe — sometimes life-threatening — infections include:
Infants younger than 6 months of age
Children with underlying conditions such as congenital heart or lung disease
Children with weakened immune systems, such as those undergoing chemotherapy or transplantation
Children who were born prematurely.