|Questions And Answers:
Detection And Control Of Influenza Outbreaks In
Acute Care Facilities
is the impact of influenza and who is at risk?
epidemics cause infection in 10-20 % of the population and result in an
average of >110,000 hospitalizations and 20,000 deaths in the United States.
Persons most susceptible to complications or death from influenza are:
>50 years of age
<2 years of age
of any age with chronic
What are the symptoms of influenza infection?
is a respiratory illness characterized by the abrupt onset of fever, chills,
headache, body aches, and fatigue with accompanying cough, sore throat,
and nasal congestion. While the fever, body aches, and headache may typically
last for three to five days, the cough and fatigue may last for more than
two weeks. Some persons may not have typical influenza symptoms, but present
with worsening of chronic
medical conditions. Some children primarily may have fever, with nausea,
vomiting or abdominal pain, and infants may have symptoms similar to a
severe systemic bacterial infection.
What are the complications from influenza infection?
common complications are secondary bacterial pneumonia and worsening of
chronic medical conditions. Influenza virus also can cause primary pneumonia, but is much less common. Rarely, children taking aspirin can develop
Reye's syndrome if they get sick with influenza.
How is influenza transmitted?
is easily transmitted from person-to-person. The virus is spread primarily
by the coughing and sneezing of infected persons or sometimes, by direct
contact, either with infected persons or a contaminated surface. Once
influenza is introduced into a facility by infected healthcare personnel,
patients, or visitors, it can quickly spread and cause illness in other
hospitalized patients and healthcare personnel, especially in those who
are unvaccinated. During a hospital ward or nursing home outbreak, as
many as 70% of staff and patients may become infected.
What is the incubation period for influenza and how long is a person contagious?
persons start to develop symptoms 1-4 days after they are exposed. They
may be able to spread influenza to other people from the day before getting
symptoms through 5-7 days after symptoms start. Children may be contagious
for 7 or more days.
How can influenza outbreaks in health care facilities be prevented?
most important means to prevent influenza illness from spreading in a
health care facility is influenza vaccination of both patients and healthcare
Advisory Committee on Immunization Practices recommends annual vaccination
of all healthcare personnel. However, in part due to low vaccination rates,
less than 100% efficacy, and because influenza-infected patients will
be admitted from the community, outbreaks of influenza can occur. When
influenza is introduced into a health care facility, prompt recognition
of influenza infection and initiation of infection control measures can
limit the spread of disease.
Why should acute care facilities conduct surveillance for influenza and
surveillance program for influenza and influenza-like
illness can help acute care facilities identify outbreaks of influenza
early in their course and prevent influenza from spreading to patients
and healthcare personnel, thereby decreasing influenza-related complications
among patients and reducing work absenteeism. When the onset of influenza
season in the community is identified, facility leaders should initiate
measures to increase awareness and intensify efforts to diagnose and prevent
influenza illness in both patients and healthcare personnel.
How should surveillance be conducted?
can be conducted in a number of settings including: 1)
incidence of reported influenza and influenza-like
case definitions for healthcare facility-acquired and community-acquired
patients who develop influenza-like
illness >72 hours after facility admission as potential cases
of health care facility-acquired influenza-like illness.
influenza testing and droplet precautions when healthcare facility-acquired
influenza is detected during surveillance, particularly when:
or more patients are identified with healthcare facility-acquired
laboratory confirmed influenza
cluster of (e.g., >3) patients with healthcare facility-acquired
illness are identified on the same floor or ward during a short
(e.g., 48-72 hour) period.
daily monitoring for influenza-like illness in selected settings, especially
on wards with particularly vulnerable patients, such as intensive care
units, oncology units, and other "sentinel" floors.
whether infection control measures are properly instituted for influenza-positive
patients, and investigate whether the infection was acquired in the
community or while hospitalized.
requiring that healthcare personnel with influenza-like
illness go to employee health services for influenza testing.
healthcare personnel who test influenza-positive or have influenza-like
illness from care of patients at high risk for influenza complications.
Emergency Department surveillance
influenza testing of patients being admitted from the emergency department
who have influenza-like
illness with no other identified pathogen.
the timely initiation of droplet precautions, through early diagnosis
among patients being admitted, to lessen the chance of influenza spreading
to personnel or other patients.
control personnel should be in regular contact with laboratory personnel
regarding influenza-positive specimens.
clinical personnel regularly about the availability and use of diagnostic
When should surveillance be conducted?
facilities should conduct surveillance for health care facility-acquired
influenza or influenza-like
illness, particularly during the influenza season from October through
April. However, sporadic cases of influenza can occur at any time of the
Why is laboratory testing for influenza important?
is very difficult to diagnose on the basis of clinical symptoms alone.
Other pathogens that can cause similar symptoms include, but are not limited
to, Mycoplasma pneumoniae, adenovirus, respiratory syncytial virus,
rhinovirus, parainfluenza viruses, and Legionella spp.
When should influenza testing be done?
facility surveillance, infection control personnel should develop threshold
levels of influenza or influenza-like
illness at which influenza testing and outbreak control measures should
be initiated. Physicians may have a lower threshold for testing individuals
at high risk for influenza-related complications. Droplet precautions
should be initiated pending laboratory confirmation of influenza.
What laboratory tests can be used to confirm the diagnosis of influenza?
samples to collect can include a nasopharyngeal or throat swab, from adults
or nasal wash, or nasal aspirates, depending on which rapid test is used.
Samples should be collected within the first 4 days of illness. Rapid
influenza tests provide results within 24 hours; viral culture provides
results in 3-10 days. Most of the rapid tests are approximately >70% sensitive
for detecting influenza and approximately >90% specific. Because as many
as 30% of samples that would be positive for influenza by viral culture
may give a negative rapid test result, negative rapid tests should be
followed by viral culture in a sub-sample of the swabs collected. Viral
culture can also identify other causes of influenza-like
illness when influenza is not the cause.
can be tested for influenza antibody to diagnose acute infections. Two
samples should be collected per person: one sample within the first week
of illness and a second sample 2-4 weeks later. If antibody levels increase
from the first to the second sample, influenza infection likely occurred.
Because of the length of time needed for a diagnosis of influenza by serologic
testing, other diagnostic testing should be used for rapid detection of
on influenza laboratory diagnostic procedures at the end of the document.
What control measures should be used for influenza or influenza-like
those with influenza or influenza-like illness together on a ward designated
to accept patients with suspected or confirmed influenza.
droplet precautions for persons with influenza-like illness or confirmed
influenza infection, including wearing masks when within 3 feet of the
patient, wearing gowns if clothing is likely to be soiled by body fluids,
and washing hands before and after patient contact.
influenza vaccine to patients and healthcare personnel who have not been
vaccinated. Healthcare personnel vaccination is critical in preventing
antiviral medications for treatment of ill patients and healthcare
personnel and for prophylaxis of exposed patients, unvaccinated personnel,
and those vaccinated <2 weeks before exposure.
personnel for influenza-like illness and restrict ill personnel from patient
visitors with influenza-like illness.
to monitor for healthcare facility-acquired influenza and for patients
being admitted to the facility who have influenza infection.
What can acute care facilities do to prepare for possible influenza outbreaks?
Make sure that all personnel receive influenza vaccination by:
access to vaccine (e.g., using a mobile cart to vaccinate healthcare
personnel in their work areas, at conferences, in lunchrooms, or in
other meeting areas).
reminders from the employee health department to all healthcare personnel
and their supervisors. The reminders should include a list of places
and times that vaccination will be offered.
providing reports of vaccination levels by employee unit. Information
should be disseminated to personnel and their supervisors and may be
used to foster a spirit of competition. Set target vaccination goals
and publicize running vaccination totals throughout the facility during
vaccination periods. Nominal awards may be beneficial in improving coverage
and should be considered. Recognition should be given to employee units
with high coverage levels.
personnel annually about the risks of influenza to their patients, themselves,
and their families, and about the benefits of vaccination. Personnel
should receive data about the impact of influenza, if known, in their
facility. Ideally, vaccination should be offered at the end of such
Offer vaccine to unvaccinated patients before they are discharged.
a written policy concerning influenza outbreak management and ensure that
key healthcare personnel, especially nurses, are aware of it.
information about influenza testing and use of influenza antiviral medication
surveillance for influenza-like
illness among healthcare personnel and patients.
diagnostic procedures for influenza1
||A and B
||A and B
|Influenza A (EIA)
Enzyme Immuno Assay
|A and B
|FLU OIA (Biostar)
||A and B4
|Quick Vue (Quidel)
||A and B4
|Zstat Flu (ZymeTx)
||A and B4
||A and B
||A and B
||paired acute and
List may not include all test kits approved by the U.S. Food and Drug
2 NP = nasopharyngeal
3 Shell vial culture, if available, may reduce time for results
to 2 days
4 Does not distinguish between influenza A and B types
5 A fourfold or greater rise in antibody titer from the acute-
(collected within the 1st week of illness) to the convalescent-phase (collected
2-4 weeks after the acute sample) samples is indicative of recent infection.