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Prevention
and Control of Influenza
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As another flu season
approaches, the Advisory Committee on Immunization Practices (ACIP) has
published a comprehensive guide to preventing and controlling outbreaks
of the illness. The report notes that in the United States, annual epidemics
of influenza occur typically during the late fall and winter seasons,
with rates of infection highest in children.
The best way to prevent
flu and its possible serious complications is vaccination, the report
advises, and vaccination is recommended for all children six months to
four years of age and for schoolchildren up to 18 years of age. Vaccination
is also recommended for some special groups, including:
- Children and adolescents
receiving long-term aspirin therapy who therefore might be at risk for
developing Reye syndrome after influenza virus infection;
- Adults and children
who have chronic pulmonary or metabolic disorders (including asthma
and diabetes);
- Adults and children
who have immunosuppression caused by medication or by HIV;
- Adults and children
who have any condition (e.g., cognitive dysfunction, spinal and cord
injuries, seizure disorders, or other neuromuscular disorders) that
can compromise respiratory function;
- Health care personnel;
- Healthy household
contacts, including children, and caregivers of children up to five
years of age, with particular emphasis on vaccinating contacts of children
under six months of age.
The ACIP offers a
refresher on the background and epidemiology of influenza. The report
notes that there are two types of viruses that cause human infection,
A and B, subtypes of which circulate globally. Annual vaccinations are
required because new influenza variants regularly emerge, as the result
of mutations that occur during viral replication.
As for the epidemiology--influenza
spreads from person to person primarily through "large-particle respiratory
droplet transmission" as when an infected person coughs or sneezes
near a susceptible person. Droplets do not remain suspended in air and
usually travel only a short distance. It's also possible to come into
contact with droplets on a contaminated surface. The typical incubation
period for the flu is one to four days, with an average of two days. Adults
can be infectious from the day before symptoms begin and through approximately
five days after illness onset. Young children also might shed virus several
days before illness onset, and children can be infectious for as much
as ten days after onset of symptoms.
The clinical signs
of influenza are well known to most people-fever, headache, malaise, nonproductive
cough, sore throat, and a runny nose, for example. But there are considerable
variations in symptoms, and studies of adults and children who were thought
to have the flu have shown that laboratory confirmation is needed in many
cases. That could be important, because an attack of influenza can result
in hospitalization or death. For children, rates of hospitalization are
higher among young children than older children; and while influenza-related
deaths are uncommon among children, they represent a substantial proportion
of all flu-associated deaths and often occur in children who have no known
risk factors for complications.
Prevention
Strategies
Stressing that annual
vaccination is far and away the best way to avoid getting the flu, the
report also mentions some other prevention strategies, including two that
are reasonable and inexpensive-frequent handwashing and "improved
respiratory hygiene," which might include teaching children to cough
or sneeze into tissues. Antiviral drugs used to treat influenza are no
substitute for vaccination, and it's not clear if community-level interventions
such as closing schools do much to control viral transmission during typical
flu seasons, though school closings are always mentioned as a first line
of defense against any widespread influenza epidemics.
Comprehensive information
about annual influenza season is available as a Recommendation and Report
from the Advisory Committee on Immunization Practices, July 13, 2007,
at www.cdc.gov/mmwr.
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