NAME: Influenza virus

SYNONYM OR CROSS REFERENCE: Flu; Orthomyxovirus; Inhuenza virus types A, B, and C.

CHARACTERISTICS: Orthomyxoviridae; single-stranded RNA virus, segmented, 70 mm diameter, enveloped; strains of influenza A are described by geographic origin, strain number, year of isolation and hemagglutim'n (HA) and neuraminidase (NA) antigens.


PATHOGENICITY: An acute viral disease of the upper respiratory tract characterized by fever, chills, headache, myalgia, weakness, n=y nose and mild sore throat; cough can be severe; nausea and vomiting are uncommon; fatality is generally low, except in those with chronic lung or heart conditions. Strains that have recently undergone antigenic shift can be severely pathogenic (influenza epidemic of 1918).

EPIDEMOLOGY: Influenza can occur in pandemics and epidemics, localized outbreaks, and as sporadic cases; epidemics of influenza A have appeared in North America at intervals of roughly 1-3 years, influenza B every 34 yrs; mixed epidemics also occur; disease more severe in older persons, children and persons with cardiac or pulmonary conditions.

HOST RANGE: Humans; swine, horses; domestic and wild avian species.

INFECTIOUS DOSE: Influenza A2 - 790 p.f. units (nasopharyngeal route).

MODE OF TRANSMISSION: Direct contact through respiratory droplets; airborne spread among crowded populations in enclosed spaces; virus may persist for hours in dried mucus and be transmitted by direct contact.

INCUBATION PERIOD: Short, usually 1-3 days.

COMMUNICABILITY: Highly communicable; probably limited to 3 days from clinical onset.


RESERVOIR: Humans; animal reservoirs are suspected as sources of new human subtypes.

ZOONOSIS: Yes, transmission from animal to man has been demonstrated on very rare occasions.



DRUG SUSCEPTIBELITY: Type A is usually susceptible (other types are resistant) to amantadine HCI and rimantadine HCI.

SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to disinfectants - 1% sodium hypochlon'te (20% commercial bleach), 70% ethanol, glutaraldehyde, formaldehyde.

PHYSICAL INACTIVATION: Susceptible to heat (561o C for at least 30 min.) and radiation.

SURVIVAL OUTSIDE HOST: Dried mucus - several hours.


SURVEELLANCE: Monitor for symptoms of flu.

FIRST AID/TREATMENT: Fluids and rest; amantadine or rimantadine HCI useful in prevention and attenuation of Influenza A infections; antibiotic treatment for secondary bacterial pneumonia.

IMMUNIZATION: Active immunization for serotypes A and B directed primarily at persons with greatest risk of serious complication or death (certain health care personnel); effective when sufficient mass of antigen closely matches the prevailing wild strain of virus.

PROPHYLAXIS: In epidemic situation, amantadine or rimantadine HCI useful for Influenza A.


LABORATORY-ACQUIRED INFECTIONS: Not normally documented in literature, but are known to occur by informal accounts and published reports, particularly when new strains showing antigenic drift or shift are introduced into the laboratory; 15 reported cases up to 1974; animal-associated infections are not reported, however, risk is high from infected ferrets.

SOURCES/SPECIMENS: Respiratory tissues or secretions of humans or most infected animals- cloaca of many infected avian species; virus may be disseminated in multiple organs in some infected animal species.

PRIMARY HAZARDS: Inhalation of virus from aerosols generated when aspirating, dispensing, or mixing virus-infected samples; from infected animals, especially ferrets.

SPECIAL HAZARDS: Genetic manipulation of virus has unknown potential for altering host range, pathogenicity or for introducing into man transmissible viruses with novel antigenic composition.


CONTAINMENT REQUIREMENTS: Biosafety level 2 practices and containment when receiving and inoculating routine diagnostic specimens; biosafety considerations should take into account infectiousness of strains used and potential for harm to individual or society in event of a lab-acquired infection and subsequent transmission; Biosafety level 2 for research utilizing contemporary strains, with older noncontemporary human strains, with recombinants, or with animal isolates.

PROTECTIVE CLOTHTNG: Laboratory coat; gloves when contact is unavoidable; work in biosafety cabinet with gloves and gown.

OTHER PRECAUTIONS: Autopsy material should be handled in a biological safety cabinet using Biosafety Level 2 procedures.


SPILLS: Allow aerosols to settle- wearing protective clothing, gently cover spill with absorbent paper towel and apply 1% sodium hypochlorite (20% commercial bleach), starting at perimeter and working towards the center; allow sufficient contact time (30 min).

DISPOSAL: Decontaminate before disposal; steam sterilization, chemical disinfection, incineration.

STORAGE: In sealed containers that arc appropriately labeled.

Date prepared-. October 11, 1997 Prepared by: Canadian Office of Biosafety Information edited by the Colorado State University Office of Biosafety; June 16, 1998.

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