Guidelines for the Prevention and Control of Influenza Outbreaks in Residential Care Facilities for Public Health Units in Australia
1.1 Influenza
Influenza and other viral respiratory illnesses occur throughout the year but are more common from March to September. During epidemics of influenza, severe illness and deaths occur primarily among the elderly and those with underlying diseases. Estimates of the rates of influenza in residents in RCFs vary considerably due to different case definitions, different circulating viruses and different contexts. The majority of studies have examined infleunza-like illness rather than influenza. For those studies which have examined laboratory-confirmed influenza in residents in RCFs, seasonal rates of influenza vary from 2-16% of residents.1, 2 During outbreaks of influenza in RCFs, attack rates of laboratory confirmed influenza can be as high as 40%.3, 4
Rates of influenza-like illness are even greater in this population, and considerably higher than the general community.1 In the outbreaks of influenza-like illness reported in 12 RCFs in NSW in 2004, attack rates in residents varied from 3-76%, and death rates varied from 0-20%.5 Influenza case-fatality rates of up to 55% have been recorded in some RCFs.3 In the light of an increasing possibility of a pandemic, control of interpandemic influenza outbreaks amongst the highly susceptible becomes all the more important.
Residential care facilities (RCFs), are considered to be high-risk environments for influenza due to communal living arrangements and the continual close proximity of residents. Nursing homes and hostels catering for the elderly are especially high-risk environments due to the older age of residents and high prevalence of chronic medical conditions.6, 7 It is important to maintain good surveillance in RCFs for outbreaks of respiratory infections so that appropriate interventions can be promptly instituted.8
The main strategies emphasized in these guidelines to prevent and manage influenza outbreaks are vaccination prior to the influenza season and during an outbreak, the use of antiviral therapy for treatment and prophylaxis, infection control measures including restriction of movement between affected and unaffected areas, and minimizing contact between affected and unaffected persons during an outbreak.
Vaccination of persons at high risk of complications and of persons who are potentially capable of transmitting influenza to those at high risk is currently the most effective measure to reduce the impact of influenza.9, 10, 11, 12 Influenza vaccination can be administered to any person who wishes to reduce the likelihood of becoming ill with influenza. It is recommended annually for people who are at increased risk of influenza complications by the National Health and Medical Research Council and is funded by the Australian Government for these people. The 8th edition of the Australian Immunisation Handbook13 recommends that persons who provide essential community services should be considered for vaccination during an outbreak, to minimize disruption of services. It is recommended for health care workers in residential care facilities.
The effectiveness of vaccination depends on the age and immuncompetence of the recipient and the similarity between the virus strain in the vaccine and those circulating in the community. The vaccine can be 70-90% effective in preventing illness in healthy persons aged under 65. For elderly people in residential care settings the vaccine is 30-40% effective in preventing illness, 50-60% effective in preventing influenza-related hospitalisation or pneumonia, and 80% effective in preventing influenza-related death.14, 15 Two studies have demonstrated that RCFs with high rates of vaccination (above 60-80%) among residents are associated with fewer outbreaks of influenza compared with those with lower vaccination rates.16, 17 These findings are consistent with vaccination effects in other populations.18
Few studies have examined the effect of vaccinating staff in RCF influenza outbreaks, but available evidence suggests that high rates of vaccination among staff members may reduce influenza related mortality among residents.19, 20, 21 As most staff members are relatively young and healthy, they are more likely to develop protective influenza antibody titres following vaccination than are the residents for whom they provide care.13 High rates of vaccination among staff may contribute substantially to herd immunity within the facility, protecting residents by reducing the risk of the introduction and transmission of influenza. The effectiveness of Influenza vaccination in healthy adults (including health care workers) in reducing days of work absence due to respiratory infections has been demontrated.22, 23
Antiviral therapy has been recommended for use in the management of influenza outbreaks in residential care facilities both for treatment and prophylaxis.7, 24, 25 The responsibility for the provision and payment for antiviral agents and influenza vaccine will vary across jurisdictions, and this should be decided at the state and territory level. There are currently three antiviral drugs registered in Australia that are effective against influenza infection. Two are neuraminidase inhibitors26, 27 while the third is an M2 blocker (amantadine). All are active against Influenza A, while only oseltamivir and zanamivir are active against Influenza B.
In adults with influenza, antiviral drugs are effective in reducing the severity and shortening the course of illness if given within 48 hours of onset of symptoms, even in elderly adults.28, 29, 30 The effectiveness of both neuraminidase inhibitors and M2 blockers to prevent influenza ranges between 70-90%. M2 blockers such as amantadine, however, have adverse-events profiles that may limit their use in elderly patients, as well as a greater potential to facilitate emergence of resistant viruses. Of the neuraminidase inhibitors, oseltamivir may be the drug of choice because of the difficulty elderly people have in using the inhaler device through which zanamivir is administered.31
Only one randomised-controlled study has been undertaken on the use of oseltamivir to prevent influenza in elderly residents in nursing homes, which found that it was 90% effective in preventing lab-confirmed influenza.32 A number of descriptive or cohort studies have examined the use of oseltamivir and infection control measures to control outbreaks of influenza in RCFs, all of which were associated with rapid control of the influenza outbreaks.7, 24, 33, 34, 35, 36, 37, 38 It was noted that earlier detection of the outbreak and intervention with antivirals resulted in better outbreak control.37
Infection control and restriction measures to minimize contact between ill and not ill are an integral part of controlling outbreaks alongside vaccination and antiviral therapy, as these measures assist with breaking the chain of transmission of the virus.6, 21, 39
