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Nosocomial viral respiratory infections and recommendations for their control

In moderate climate areas, infection by respiratory viruses at hospital wards is observed every year. The risk of infection over the winter months could be found both in patients and hospital personnel. Nosocomial infections are most frequently observed in children at different pediatric wards followed by patients at psychiatry wards. On the other hand, hospital personnel with acute respiratory infection are the most important group from the point of view of the infection spread, and hence of the utmost importance for nosocomial infection control. Therefore, in order to decrease the frequency of nosocomial infections, it is important to provide education for hospital personnel in the etiology and the transmission mechanisms of respiratory viruses. There are two major mechanisms of transmission of respiratory viruses: 1)The first is by small-particle aerosols (10 mm in diameter) containing infectious virions. Aerosols produced by coughing, sneezing, or talking are capable of transmitting infection from one person to another over considerable distance (up to 2 m). Such a mechanism of transmission is observed, for example, in adenoviruses, influenza, varicella, mumps, rubella and measles virus. 2)The second mechanism of transmission occurs when large droplets produced by coughing or sneezing contaminate the donor"s hand and infectious virus is transferred to the mucous membrane of the susceptible (nonimmune) host. This mechanism requires close person-to-person contact (usually less than 1 m). It occurs continuously in contact with the contaminated hands or objects. Most frequently the infection is the result of autoinoculation, with transfer of virus from contaminated hands to mucous membranes of the host"s eye or nose. Such transmission mechanisms are observed in rhinoviruses, parainfluenza viruses and respiratory syncytial virus. Influenza viruses and other viruses transmitted by aerosols Influenza viruses infections are among the most contagious diseases of man (influenza A and B, measles, mumps, rubella, adenoinfections and other infectious diseases). Influenza epidemics occur in winter months (in Croatia, the epidemic peak has usually been observed in January, but it may occur from December to March: : Mlinarić-Galinović G, Ugrčić I, Detić D, Božikov J: Epidemiological picture of respiratory viral infections in Croatia. Acta Med Iugosl 1991; 45:203-211, Mlinarić-Galinović G, Turković B, Baće A, i sur.: Etiology of atypical pneumonia in children and adults. Pediatr Croat 1995; 39:247-251). Adenoviruses, especially types 1-7, 14 and 21, cause acute respiratory infections throughout the year (types 3, 4 and 7 are often observed in epidemics). The viruses are transmitted by aerosol, accounting for the explosive nature of influenza outbreak since, in a closed environment, one infected person can potentially infect large numbers of susceptibles. An influenza epidemic may result in significant morbidity and mortality, especially in the elderly and chronically ill institutionalized patients ( Mlinaric-Galinovic G, Falsey AR, Walsh EE: Respiratory syncytial virus infections in the elderly. Eur J Clin Microbiol Infect Dis 1996; 15: 777-781). Influenza infections are often observed at psychiatry and even more often at pediatric wards ( Beritić B, Mlinarić-Galinović G, Ugrčić I: Nosokomijalne virusne infekcije respiratornog trakta na dječjem odjelu. Jugoslavenska pedijatrija 1988; 31:105-107). Isolation precautions. Guidelines by the Centers for Disease Control (CDC), Atlanta, GA, USA, recommend wearing masks for hospital personnel and isolation of patients in separate rooms when the infection is etiologically established. In outbreaks of influenza, when large numbers of patients are hospitalized, it is recommended to put such patients together in rooms of the same hospital floor. Administration of amantadine in specific therapy of influenza might shorten the virus secretion time. Immunization. Vaccination in autumn, for the elderly and chronically ill, provides for 60-90% of influenza A and B prevention. Hospital personnel, being mainly young and healthy, undergoes influenza relatively easily. However, it is recommended to do vaccination for hospital personnel to prevent high exposure to viruses and further spread of the infection. Although there exists a live attenuated vaccine for adenovirus types 3, 4, and 7, these are not applied in this context. Chemoprophylaxis. Amantadine hydrochloride in 80% of cases prevents nosocomial influenza A virus infection. The usual dose of amantadine is 200 mg per day in either a single or divided dose. If hospital personnel is not vaccinated, amantadine is administered for the duration of the outbreak. Other control measures. During influenza outbreak, depending on the severity of the outbreak, it is recommended: 1)To cancel medical examinations and surgical procedures, 2)To cancel visits to patients, 3)To restrict work for medical personnel with acute respiratory disease. Respiratory syncytial virus (RSV) and other viruses transmitted by large droplets RSV is the most common cause of lower respiratory tract disease in children less than 2 years of age and may account for up to 50% of all hospital admissions for respiratory disease in this age group. At the same time, it is the most common nosocomial infection at pediatric wards (Mlinarić-Galinović G, Ugrčić I, Kovačić V, i sur.: Etiološka dijagnostika i učestalost infekcija respiratornim sincicijskim virusom u SR Hrvatskoj. Liječ Vjesn 1986; 1o8:289-295, Beritić B, Mlinarić-Galinović G, Ugrčić I: Nosokomijalne virusne infekcije respiratornog trakta na dječjem odjelu. Jugoslavenska pedijatrija 1988; 31:105-107, Mlinaric-Galinovic G: Analysis of respiratory syncytial virus outbreak in neonates. LabMedica International Sep-Oct 1995; 16-19, Mlinarić-Galinović G, Polak-Babić J, Pleše M, i sur.: Respiratory syncytial virus infection in neonatal units. Cro Med J 1994; (3): 168-171). People in all age groups are susceptible to RSV but many reinfections are clinically mild diseases. However, in the elderly of 65 years of age, they might develop into atypical pneumonia (Mlinaric-Galinovic G, Falsey AR, Walsh EE: Respiratory syncytial virus infections in the elderly. Eur J Clin Microbiol Infect Dis 1996; 15: 777-781). Outbreaks of RSV in Croatia has shown the peak in December or early spring months. Parainfluenza virus types 1, 2 and 3 are very significant causes of croup (often types 1 and 2) in infants, and bronchiolitis (type 3) in neonates. Type 3 virus could be observed throughout the year, but types 1 and 2 occur in seasonal outbreaks. Rhinoviruses (119 types) are causal agents of colds and circulate in winter months. Children produce 7-21 days large amounts of virus nasal droplets. Spread of the virus by large droplets and the frequent autoinoculation to mucous membrane of the nose and eyes are made possible since survival time in external environment of this extremely delicate virus is shown to be up to 6 hours. Isolation precautions. Children with established RSV or parainfluenza infections should be put into separate rooms or kept with other children with the same disease. Hospital personnel should practice handwashing, changing of clothes and gloves after handling such patients. Children"s toys and other objects should not be moved from one bed to another. Masks are not among the protection options for this type of infection. Education of hospital personnel on the virus spread is of considerable importance. Immunization is not applied so far, and neither the specific chemoprophylaxis (in RSV infections, therapy is ribavirin in the form of aerosol, administered in the air-filled balloon over three days).

nosocomial infections; viruses; respiratory syncytial virus (RSV); influenza virus; infection control

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