Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is an RNA virus. It is commonly known to cause bronchiolitis, an inflammation of the respiratory tract that affects the smallest airway passages of the lungs (bronchioles). RSV infection is a common pediatric illness that affects thousands of children every year. While most of them never require hospitalization, some are sick enough to be hospitalized in the intensive care units. At this point, let me share with you about an incident that happened a few years ago while I was doing my internship.

This is a case about a 5 month old boy, Aniruddh (name changed). Aniruddh was born prematurely at 34 weeks to a couple who were manual laborers. He had 2 sisters, both studying at a school nearby. He had been well breast fed and apparently was doing well until a week ago when he developed low to high grade fever. The parents were not concerned until he developed noisy breathing 2 days before he was brought to the out-patient department of a hospital. Furthermore, his activities and feeding had reduced significantly; he had mild unproductive cough, no diarrhea or vomiting. He had been urinating less frequently. On examination, Aniruddh was febrile with a temperature of around 103°F, where pulse and breathing was rapid. Wheezing sound was heard from the chest while auscultating the respiratory system. Systemic examination was normal. We decided to hospitalize him and monitor him since he looked weak and had not been feeding well. Supportive treatment with intravenous fluid, oxygen, antipyretic agents was started. Blood investigations were normal. Chest x-ray showed opacities around perihilar region.

Unlike what we had expected, this boy remained symptomatic the next day; in fact, his breathing worsened. He found it difficult to breathe; his wheezing became more pronounced and was developing respiratory distress. Peripheral oxygen saturation levels dropped below 80 which disturbed us. He was shifted into the intensive care unit and was put on positive pressure ventilation. Bronchodilator and adrenaline nebulization was started. Further investigation revealed viral bronchiolitis. There was not much change for the next 2-3 days. However, Aniruddh did improve a few days later and he was discharged a week after that from the hospital.

Aniruddh was one of the many children who had suffered from acute bronchiolitis caused by respiratory syncytial virus (as indicated by viral marker tests).

Just like Aniruddh, there are many more children who suffer every year especially during winter.

The symptoms indicative of respiratory syncytial virus infection are:

• Cough
• Coryza (running nose)
• Fever
• Wheezing

If your child had similar symptoms and if he or she was born prematurely, beware; it could be RSV infection. It usually is a self limiting illness which fades away uneventfully, but in rare cases, it can cause serious illnesses which are potentially life threatening.

How does respiratory syncytial virus cause infection?
Well, this virus spreads through direct contact. After entry into the child, it incubates for 2-8 days before producing symptoms. Initially the virus replication begins in the nose and nasopharynx. The next few days, the virus trickles down into the airways of the lungs. The tiny airways are more commonly affected. Infection leads to swelling of the airway and increases mucus production, which are responsible for both breathing difficulty and wheezing. Eventually tissue necrosis takes place and heals through regeneration.

There are two subtypes of this virus: subtype A and subtype B, where subtype A is more virulent. As the immunity from an acute infection fades away more quickly, it is common to see multiple episodes of RSV bronchiolitis in a child.

What are the risk factors of RSV infection?
As discussed in Aniruddh’s case, this infection is more common among infants and children below 5 years. Those born prematurely before 35 weeks of pregnancy are commonly affected. The virus is ubiquitous and favors the cold winter environment. Therefore, in the northern hemisphere this infection is usually seen from November to April. Other risk factors include low socioeconomic status, malnourishment, presence of congenital heart defects and co-existing respiratory ailment, in-utero exposure to tobacco and immunocompromization.

Though adults are less commonly affected, HIV and other immunocompromised status predisposes adults to RSV infection.

How is RSV diagnosed?
RSV is often diagnosed clinically. A child with associated risk factors like fever and wheezing should be evaluated for RSV infection.
Tests available as evidence to support clinical diagnosis are:

• Chest x-ray
• Viral study – direct fluorescent antibody detection
• Chromatographic rapid antigen detection
• RNA PCR test

Treatment:
In most cases symptoms resolve spontaneously. If case hospitalization is required, the current treatment preferred is nebulized hypertonic saline (3% hypertonic saline) along with oxygen, fluid, bronchodilator and epinephrine nebulization.

Prevention:
Currently there are no vaccines available against RSV infection. However, monoclonal antibody palivizumab is available as monthly injection and should be used in children born prematurely. Palivizumab prophylaxis is revealed to lower incidence of future RSV infection.

Besides, these viruses spread mainly by droplets made when people with flu cough, sneeze, talk etc., and through direct contact during the first 8 to 10 days of the infection. Hence, good hygiene and isolation of the affected patient can prevent the spread of RSV.