Not Just a Chest Cold: Respiratory Syncytial Virus

The respiratory syncytial virus is a labile paramyxovirus of negative-sense, enveloped RNA (RSV, 2007). The virus effects both the upper and lower respiratory tracts. The size and shape of the virus is variable (120-300 nm) and highly unstable, surviving only a few hours outside of the body and succumbing quickly to soap and water or disinfectants (Respiratory, 2007). This virus demonstrates the syncytial effect in tissue culture, causing a characteristic fusion of human cells.

There are two subtypes of the virus, type A (RAV) and type B (RBV). RAV is responsible for most subclinical or asymptomatic RSV infections. RBV is the main culprit in the annual outbreaks of RSV pneumonia and bronchiolitis that hits every year for 4-6 months in the cold weather season. Most children have had an RSV infection by 3 years of age, many of which progress to bronchiolitis or pneumonia (RSV, 2007). The virus is self-limiting with an 8-15 day duration. Most lower respiratory infections (LRI) are caused by viruses, with RSV as the responsible microbe for most childhood LRI (Respiratory, 2007).

Mode of Transmission

Transmission of the virus is achieved through direct or indirect contact with an infected person's secretions (Frazier & Drzymkowski, 2004). This can mean a kiss, inanimate vectors, inhalation of respiratory or nasal droplets that become airborne through a cough or sneeze, or a handshake later followed by contact between the affected hand and the mucous membranes of the eye, nose, or mouth (Respiratory, 2007). Healthcare professionals are frequent vectors of RSV transmission in hospital-related infection (RSV Info, 2007).

Annual outbreaks tend to last 4-6 months during fall, winter, and early spring. The timing and severity of illness is variable. Most children have serologic evidence of infection by two years old (Respiratory, 2007). RSV has a 3-5 day incubation period. The virus is shed through respiratory and nasal droplets1-2 days before symptoms and for two weeks after symptom onset. The period of shedding lasts longer in immunocompromised patients (RSV, 2007).

At Risk

RSV infection is most common in the very young: although one can have a severe LRI at any age. Premature infants and those less than one year of age, or the elderly are at high risk. This illness is common among children who are exposed to second hand smoke, attend daycare, have older siblings in the home, were unbreastfed, of lower socio-economic status, and those who live in crowded conditions. Also at risk for severe infection are people with cystic fibrosis, or compromised cardiac, pulmonary, or immune function (RSV, 2007).

Signs and Symptoms

Initial symptoms resemble a cold. The patient may experience runny nose, mild cough, low-grade fever, and maybe wheezing (25-40%) (Respiratory, 2007). Infants frequently experience otitis media. When the infection progresses the nasal discharge and lung expulsions will take on a yellow, green, or gray appearance. The respiratory rate increases, respiratory muscles retract and nostrils flare, indicating a lower respiratory infection. There could be a hyperexpansion of the chest, hyper-resonance or dullness to percussion, chest pain, crackling, nasal congestion, lethargy, or dyspnea. Apnea, cyanosis, irritability, and restlessness may be present in cases of impending respiratory failure (RSV, 2007).

Diagnosis

Diagnosis is achieved through clinical findings, physical exam. Lavage of the nasopharynx is performed for a slide stain analysis and growth in a tissue culture. The culture grows giant syncytial (fused) cells characteristic of RSV infection (Frazier & Drzymkowski, 2004).

Other methods of diagnosis include virus isolation detection of v-antigens or RNA, a rise in serum antibodies or a combination of the most used antigen detection assays (Respiratory, 2007). These assays run from 25-75 minutes in duration. They include the Solid-Phase Enzyme Immunoassay, Enzyme Immunoassay Membrane filter, Monoclonal Antibody-based Enzyme Immunoassay, and Immunoflourescence (RSV, 2007).

Treatment

For mild infections treat the symptoms. Use antipyretics for fever, antibiotics for otitis media, inhalation therapy, and sufficient liquid intake (Respiratory, 2007). Raising the head of the bed aids in breathing (Frazier & Drzymkowski, 2004). Severe infections may require hospitalization for oxygen therapy, mechanical ventilation, or rehydration.

Drug interventions include Ribavirin aerosol, immune-globulin intravenously (IGIV) with high titers of RSV antibodies for a viral neutralizing effect. Ribavirin is administered to immunocompromised patients (Respiratory, 2007). Palivizumab and RSV-IGIV have recently been licensed for use in high-risk patents before infection. This prophylactic use of these medications has shown a 45-55% decrease in hospitalization due to RSV in recent clinical trials (Pediatrics, 2007). These anti-viral agents also reduce the risk of long-term sequelae associated with RSV infection. Morbidity may be reduced with aggressive medical intervention and early treatment with broad-spectrum anti-virals (RSV Info, 2007).

Prognosis

The prognosis for RSV infection is good, barring serious complications (Frazier & Drzymkowski, 2004). .5-2% of all cases are hospitalized, most of which are under six months of age. Doctors should consider RSV early in the illness. Each patient is at risk for repeated infections, with moderate to severe cold-like symptoms throughout life (Respiratory, 2007). Common sequelae to RSV include bronchiolitis throughout the first year (with or without hospitalization), Reactive Airway Disease, pulmonary function deficits, asthma, hyperinflation, variable airways obstruction, bronchial reactivity, acute respiratory; disease, and COPD (RSV Info, 2007). There exists a broad spectrum of RSV infections, ranging from mild to fatal.

Prevention

There is currently no vaccine for RSV. Thorough and frequent hand washing is stressed. Limit person-to-person contact with the infected individual. Refrain from handling infants or sharing eating and drinking utensils if you have a respiratory infection (Respiratory, 2007). RSV-IGIV or anti-RSV humanized murine monoclonal antibodies can be given to high-risk individuals to prevent serious complications (Pediatrics, 2007). When these individuals must be in the hospital, use gowns and gloves (Respiratory, 2007).

Works Cited
M.S. Frazier & J.W. Drzymkowski (2004). Essentials of Human Diseases or Conditions 3rd ed. Elsevier Saunders, Missouri.

Pediatrics Vol. 112 No. 6. Retrieved on 5/7/07.
http://pediatrics.aappublications.org/cgi/content/abstract/112/6/1447

Respiratory Syncytial Virus. Retrieved on 5/7/07. http://www.cdc.gov/ncidod/dvrd/revb/respiratory/rsvfeat.htm

RSV. Retrieved on 5/7/07.

http://www.rsvinfo.com/diagnosing/diagnosing.html

RSV Info Center. Retrieved on 5/7/07.

http://www.rsvinfo.com/sequelae/sequelae.html