Respiratory Syncytial Virus - Term Paper Example

?Respiratory Syncytial Virus Overview Respiratory syncytial virus or RSV is a leading cause of lower respiratory tract infection in young children and infants (Ji et al, 2009). The infection mainly manifests as viral pneumonia or bronchiolitis. The infection is usually mild, however, it can also be very severe necessitating admission to critical care units. As of now, there is no vaccine for RSV infection and the vaccine is under the development stage (Krilov, 2011). Epidemiology Peak incidence occurs between 2-8 years of age (Fryzek et al, 2011). In the United States, more than 4 million children ages less than 4 years of age acquire this infection and more than 125, 000 children get hospitalized because of this infection (Krilov, 2011). Almost every child will have atleast one RSV infection in the first 3 years of life (Krilov, 2011). The disease is prevalent in most parts of the world and is associated with some morbidity and mortality. Mortality rate however is low and less than 1 percent even in hospitalized children. Increased mortality is seen only in high risk groups like immunodeficiency, chronic lung disease and prematurity (Marlais et al, 2011). In these children, even the hospital stay is prolonged. There is some evidence that infants who have suffered RSV infection are likely to develop abnormal pulmonary function tests related to asthma or obstructive disease (Krilov, 2011). It is yet unclear whether the virus itself causes the disease are those who have such problems are prone to the disease. The disease occurs in all races and both the sexes. Reinfection can occur any time in life, with limitation to upper respiratory tract. Virology The virus has 10 genes which encode 11 proteins, M2 has 2 open reading frames. NS_ and 2 inhibit the activity of interferon-1. N encodes for the nucleocapsid protein resulting in association with the genomic RNA, forming nucleocapsid. The matrix protein that is essential for viral assembly is encoded by M. The viral coat is formed by G, SH and F. G is the surface protein and is glycosylated heavily. It mainly functions as the protein of attachment. F is also a surface protein. It mainly mediated fusion and helps in the entry of the virus into the cell and also transfer of the virus from one cell to another through syncytia (Ji, 2009). Site of infection Infection due to RSV is restricted to the respiratory tract. In young children and infant, the lower respiratory tract gets involved. The virus gets inoculated in the epithelial cells of the upper respiratory tract and the virus gradually spreads to the lower respiratory tract through cell-to-cell transfer along the syncytia (Garzon et al, 2002). Clinical presentation Clinically, the child begins with symptoms of upper respiratory tract infection and small airway disease many manifest within 2 days. Clinical features include coryza, cough, wheezing, few crepitations, low grade fever and poor appetite. In some children, the disease is advanced and manifests as retractions, cyanosis and low oxygen saturations on oximetry. Secondary bacterial infections are rare with RSV infection, except for otitis media which occurs in 40 percent cases. In very small infants apnea and sepsis like picture can occur. In older children, RSV is more limited to upper respiratory tract. In elderly people, RSV is a severe disease (Marlais et al, 2011). In those with immunodeficiency also, severe disease occurs. Because of decreased oral intake and increased loss of water through increased breathing, children with RSV infection are likely to be dehydrated (Krilov, 2011). Risk factors Factors associated with increased risk of developing the infection are attendance to child care, lower socioeconomic status, crowding, exposure to pollutants in the environment like traffic pollutants and smoking, absence of breast feeding, multiple births sets and family history of asthma. Other risk factors include prematurity, age less than 3 months, congenital heart disease, chronic lung disease, congenital immunodeficiency and severe neuromuscular disease (Krilov, 2011). Differential diagnosis Differential diagnosis of the disease include bronchiolitis due to other causes, asthma, acute bronchitis, croup, influenza, pneumonia and neonatal sepsis (Krilov, 2011). Investigations More often than not, laboratory studies are not indicated in RSV bronchiolitis, especially in a child who is comfortable, is well hydrated and has good oral intake (Oladottir et al, 2011). Some nonspecific tests indicated depending on the clinical condition of the patient are complete blood picture, arterial blood gas and blood culture (Oladottir et al, 2011). Specific diagnostic tests for confirmation of RSV are antigen revealing tests and culture. The tests are performed on secretions from the nasopharyx and are obtained by suctioning, washing or swabbing. These tests are not routinely recommended and are performed only for educating parents, to withhold antibiotics and for isolation reasons . The most frequently used imaging study in RSV infection is chest radiography that reveals hyperinflated lung fields with increase in interstitial markings. In one fourth of the patients, pulmonary infiltrates or atelectasis may be seen. Those who have these findings are likely to have a severe course (Krilov, 2011). Histological findings have been ascertained from postmortem samples. Lung tissue is infiltrated with neutrophil and mononuclear infiltration of the peribronchial areas, small airway epithelium necrosis, neutrophil infiltration of the peribronchial areas, plugging of the lumen with edema and exudate, hyperinflation and atelectasis (Krilov, 2011). Transmission RSV is highly contagious, usually for 3-8 days. In those with immunocompromised state, it is contagious upto 4 weeks. More than 50 percent household members can get affected. However, the extent of the disease is dependent on the age group and the clinical health status. Spread of the virus occurs when the virus-containing droplets are coughed or sneezed into the air by the person who is infected. The droplets can linger in air for a brief period of time and contact of a person's eyes, mouth or nose with the particles contributes to infection. Other than droplet infection, kissing, direct contact with objects smeared with secretions from the infected person like door knob can also result in spread of the virus. The virus is a tough one and can survive in the environment for several hours (CDC, 2011). The main treatment for RSV infection is supportive care (Garzon and Wiles, 2002). Children who do not have any risk factors, can take oral fluids and are tolerating room air, must be managed on outpatient basis with close physician contact. Management at home involves making the child feel as comfortable as possible, allowing time for recovery and giving plenty of oral fluids. In winter months, using cool mist vaporiser keeps the air moist and makes the mucus stickier. Steam and hot water humidifiers can be hazardous and result in scalding and hence must be avoided. Nasal aspirator may be used to remove nasal fluids that are sticky, especially in young children who cannot blow. Supportive care in hospitalised patients includes supplemental oxygen therapy, fluid replacement and mechanical ventilation as needed. There is no clear consensus on the use of bronchodilator therapy with beta-agonists, although, many physicians prefer to give a trial of these drugs through nebulisation (Garzon and Wiles, 2002). Humidification through saline nebulisation is useful. The specific antiviral agent that has been approved for anti-RSV treatment is ribavarin (Ventre and Randolph, 2007). The drug is administered in the aerosolised form at a dose of 6 gram in 300ml distillled water over 12- 20 hours for 3-7 days. However, its use is limited in view of high cost of acquisition, tediuos administration and no evidence to prove is benefits in terms of decreased hospitalisation and mortality. There is also some evidence that it may cause secondary toxicity to health workers because of aerosolised drug particles in the air of the patient's room (Krilov, 2011). According to a cochrane review (Ventre and Randolph, 2007), ribavarin is an expensive drug and it is yet unclear whether the drug is efficacious. In the systematic review by cochrane, it was evident that the drug decreases the need for mechanical ventilation, the number of days in the hospital and also decrease in the recurrent wheezing associated with the virus. However, the studies which have been conducted in this regard are small and hence cannot be used to generalize the results. No adverse effects have been reported because of the use of the drugs (Ventre and Randolph, 2007). Prevention Frequent hand washing is the most important technique for prevention of spread of the virus. Those with illness must not share cups or utensils. Care must be taken especially with high risk groups like elderly, chronic diseases and immunodeficiency states. Palivizumad is an useful preventive agents that can be given to very high risk groups with increased risk of mortality to the infection. However, this drug has no role once the disease is contracted by the individual (CDC, 2010). Complications Complications related to RSV infections include bronchiolitis, croup, otitis media, pulmonary failure and pneumonia (Krilov, 2011). References CDC. (2010). Respiratory Syncytial Virus Infection (RSV). CDC. Retrieved on 30th March, 2011 from http://www.cdc.gov/rsv/ Fryzek, J.P., Martone, W.J., Groothuis, J.R. (2011). Trends in chronologic age and infant respiratory syncytial virus hospitalization: an 8-year cohort study. Adv Ther., 28(3):195-201. Garzon, L.S., Wiles, L. (2002). Management of respiratory syncytial virus with lower respiratory tract infection in infants and children. AACN Clin Issues, 13(3), 421-30. Ji, W., Wu, J.H., Huang, L., Luo, Y.L., Zhang, X.L. (2009). An etiological study on acute respiratory infection among inpatient children in Suzhou. Zhonghua Yu Fang Yi Xue Za Zhi, 43(10), 867-7. Krilov, L.R. (2011). Rspiratory Syncytial Virus Infection. Medscape. Emedicine from WebMD. Retrieved on 30th March, 2011 from http://emedicine.medscape.com/article/971488-overview Marlais M, Evans J, Abrahamson E. (2011). Clinical predictors of admission in infants with acute bronchiolitis. Arch Dis Child. Retrieved on 30th March, 2011 from http://www.ncbi.nlm.nih.gov/pubmed/21339199 Oladottir, Y.R., Kristjansson, S., Clausen, M. (2011). Acute bronchiolitis: Diagnosis and management. Laeknabladid, 97(3), 151-157. Ventre, K. and A. G. Randolph (2007). Ribavirin for respiratory syncytial virus infection of the lower respiratory tract in infants and young children. Retrieved on 30th March, 2011 from Cochrane.Database.Syst.Rev CD000181 (1): CD000181. Read More