Influenza Disease

BASICS

DESCRIPTION

An acute, usually self-limited, viral, febrile, infection caused by influenza virus types A and B. It is marked by inflammation of the nasal mucosa, pharynx, conjunctiva, and respiratory tract. Outbreaks occur almost every winter with varying degrees of severity.

The influenza virus displays antigenic shift (variation) which leads to strains of the virus to which there is little immunologic resistance in the population and may result in pandemics. The influenza virus displays minor antigenic variation called drift.
System(s) affected: Pulmonary
Genetics: N/A
Incidence/Prevalence in USA: 250,000-500,000 new cases each year. Attack rates in healthy children are 10-40% each year.
Predominant age:
- Incidence: highest in school-aged children (3 months–16 years); young adult (16–40 years)
- Morbidity: highest in elderly (> 75 years) and concurrent medical illnesses, such as lung disease
Predominant sex: Male = Female

SIGNS AND SYMPTOMS

Sudden onset of:

High Fever
Myalgia (sometimes severe and lasting for days)
Sore throat/pharyngitis
Nonproductive cough
Headache
Cervical lymphadenopathy
Chills
Nasal congestion
Malaise
Rhinorrhea
Sinusitis
Sneezing
Conjunctivitis

CAUSES

Orthomyxovirus (influenza antigenic types A and B) that are transmitted person-to-person, often by the airborne route

RISK FACTORS

For contracting disease:
- Patients in semi-closed environments such as nursing homes
- Students, prisoners
- Crowded, close environments during times of epidemics
For complications:
- Chronic pulmonary diseases
- Cardiovascular diseases including valvular problems and congestive heart failure
- Metabolic diseases
- Hemoglobinopathies
- Malignancies
- Pregnancy, especially in the 3rd trimester
- Neonates, elderly
- Immunosuppression

DIAGNOSIS

LABORATORY

Rapid antigen test
Culture of nasopharyngeal swab or aspirate
Lymphopenia
Leukocytosis may signal complications

Drugs that may alter lab results: N/A
Disorders that may alter lab results: N/A

PATHOLOGICAL FINDINGS

Inflammation of respiratory tract

SPECIAL TESTS

N/A

IMAGING

Chest x-ray
- Usually normal unless secondary infection
- Basilar streaking
- Patchy infiltrate - mild disease

DIAGNOSTIC PROCEDURES

Tissue culture of nasopharyngeal swab or aspirate
Rapid ELISA antigen test. Some rapid tests diagnose influenza A, while others diagnose influenza A+B.
History and physical examination - close attention to epidemiology (e.g., current outbreak in community). Contact CDC at (404)332-4555 or health department to determine type.

TREATMENT

APPROPRIATE HEALTH CARE

Outpatient except for treatment of severe complications or treatment of those in high risk groups

GENERAL MEASURES

Symptomatic treatment (saline nasal spray, analgesic gargle)
Cool-mist, ultrasonic humidifier to increase moisture of inspired air
Modified respiratory isolation techniques
Hospitalized patients may require oxygen or ventilatory support
Avoid smoking

SURGICAL MEASURES

N/A

ACTIVITY

As tolerated. Hospitalized individuals should have contact isolation with strict hand washing procedures.

DIET

Increase fluid intake

PATIENT EDUCATION

For a listing of sources for patient education materials favorably reviewed on this topic, physicians may contact: American Academy of Family Physicians Foundation, P.O. Box 8418, Kansas City, MO 64114, (800)274-2237, ext. 4400
Educate high-risk patients about prevention

FOLLOW UP

PREVENTION/AVOIDANCE

Incubation - 1 to 4 days; infected persons most contagious during peak symptoms
Polyvalent ´influenza vaccine´
- Recommended for all adults age 50 and older
- Recommended for high risk individuals: chronic pulmonary disease, cardiovascular disease, immunosuppression, hemoglobinopathies, renal diseases, metabolic disease, diabetes, HIV, long term aspirin therapy, asplenia, alcoholism
- Recommended for health care providers, home care providers, staff and residents of nursing homes and other chronic care facilities, homeless, public safety workers and close contacts of high risk individuals
- Should be administered in the Fall prior to influenza season
- Some side effects possible, e.g., fever and mild, local reaction at vaccination site.
- Two vaccines: Whole and split virus
  - Split vaccine for children < 13 years old; adults may receive either vaccine.
  - Dose is 0.5 IM except for children < 3 years old. Children 6 through 35 months old should receive 0.25 mL.
  - Single dose/year except for children < 9 years old who should receive 2 doses the first year that they receive influenza vaccine (1 month apart)
  - Vaccine contraindications: Anaphylaxis to eggs (do skin testing first)
  - 2 weeks after immunization before protection occurs
Amantadine and rimantadine:
- May be used prophylactically in high risk groups (that have not been vaccinated or need additional control measures) during epidemics of influenza A (ineffective against influenza B). It should not be considered as a substitute for vaccination unless vaccine contraindicated.
- Take for duration of outbreak, if no vaccine given. Discontinue after 14 days if used in addition to vaccine.
- Prophylactically during influenza season for those with contraindications to vaccine
- Prophylactically for staff and residents in nursing home outbreaks of influenza type A
- Protective efficacy about 80% for type A influenza virus only

POSSIBLE COMPLICATIONS

Otitis media
Pneumonia
Reye's syndrome
Rhabdomyolysis
Post-influenza asthenia
Acute sinusitis
Croup
Apnea in neonates
Bronchitis
Death
Exacerbation of CHF

EXPECTED COURSE AND PROGNOSIS

Favorable

MISCELLANEOUS

ASSOCIATED CONDITIONS

Bacterial pneumonia

AGE-RELATED FACTORS

Pediatric: Reye's syndrome is a rare and severe complication associated with aspirin use. Avoid aspirin in children with influenza.
Geriatric:

Elderly more likely to have complications
Immunization recommended age 50 and older

Others: N/A

PREGNANCY

Women at risk from influenza complications should receive influenza vaccine regardless of trimester
ACIP recommends vaccinating all women who will be in the second or third trimester of pregnancy during influenza season
Amantadine is contraindicated in pregnant women

OTHER NOTES

Persons with HIV infection should get annual influenza vaccination, however the antibody response to the vaccine may be low in persons with advanced HIV-related illnesses

ABBREVIATIONS

N/A

Clinical Investigations

ROLE OF HOMOEOPATHY

Holistic healing that treats the person, not just the disease. Experience gentle, lasting wellness with expert constitutional care.