NAME: Influenza virus (B and C).
SYNONYM OR CROSS REFERENCE: Orthomyxovirus, grippe, pleural infusion, pharyngitis, upper respiratory tract infection, and flu Footnote 1.
CHARACTERISTICS: Members of the Orthomyxoviridae family of segmented, negative sense, single-stranded RNA viruses Footnote 1, Footnote 2. Minor changes (antigenic drift) in the surface antigenic configuration may occur in influenza B and influenza C viruses, giving rise to variations in virus stain Footnote 3. Comparisons of the sequence divergence among the genes of influenza viruses belonging to type A, B and C suggest that, in humans, influenza B viruses evolve more slowly than influenza A viruses and faster than C viruses Footnote 4.
PATHOGENICITY/TOXICITY: Influenza B is an acute viral disease of the upper respiratory tract characterized by acute fever, chills, headache, myalgia, weakness, runny nose, sore throat, and cough (can be severe). Nausea and vomiting are uncommon, except in children, and fatality is generally low, except in those with chronic lung or heart conditions Footnote 1. Recovery is usually rapid, but the cough may persist for some time. Influenza B causes the same spectrum of disease as influenza A but does not cause pandemics. Influenza C virus causes a mild upper respiratory tract infection with fever, cough and rhinorrhea being the most common symptoms Footnote 3.
EPIDEMIOLOGY: Influenza B can occur in epidemics, but serious disease with influenza B is rare and is usually confined to the elderly Footnote 3. Influenza B disease is common in children and young adults, and causes seasonal epidemics every 2–4 years Footnote 5. Influenza B viruses were the most commonly reported influenza type in Europe for the 20005-06 season Footnote 6. In Canada, in the 2007-08 influenza season, it was reported that 42.1% of all influenza detections were influenza b viruses Footnote 7. Influenza C has been associated with sporadic cases and minor localized outbreaks, but has never been associated with epidemic outbreaks and a large proportion of influenza C infections are clinically unapparent Footnote 1.
HOST RANGE: Influenza B and C viruses are found almost exclusively in humans; however, there are reports of the isolation of B virus from horses and seals Footnote 1, Footnote 8, Footnote 9, and C virus from swine Footnote 1.
INFECTIOUS DOSE: Unknown.
MODE OF TRANSMISSION: Transmission of influenza in humans can occur via droplets (from coughing and sneezing) or from contact with contaminated surfaces Footnote 1, Footnote 10. Closed environments and crowds favour transmission Footnote 1. Influenza virus can persist for 2 to 8 hours on stainless steel surfaces and for a few minutes on paper tissues Footnote 10, Footnote 11.
INCUBATION PERIOD: One to 3 days Footnote 1.
COMMUNICABILITY: Highly communicable, probably limited to 3 to 5 days from clinical onset, and up to 7 days in young children Footnote 12.
RESERVOIR: Humans. There is no recognised zoonotic reservoir; however, swine are suspected as sources of new human subtypes Footnote 1. In addition, antibodies to influenza B and C viruses have been detected in horses and dogs Footnote 1, and influenza B infection has been documented in seals Footnote 1, Footnote 8, Footnote 9 which are touted as a potential reservoir of influenza B Footnote 9.
DRUG SUSCEPTIBILITY: The main antiviral agents to treat influenza B available in the United States and Canada are the neuraminidase inhibitors, zanamivir and oseltamivir Footnote 15. Oseltamivir is licensed in Canada for treatment and post-exposure prophylaxis, and zanamivir for treatment and prophylaxis Footnote 16, Footnote 17; however, oseltamivir is documented to be less effective for influenza B viruses than for influenza A viruses Footnote 18. The M2 inhibitor amantadine, that is often used to treat influenza A, has no affect on influenza B Footnote 11, Footnote 15, Footnote 16. Amantadine is no longer used in Canada due to resistance that develops rapidly Footnote 19.
SUSCEPTIBILITY TO DISINFECTANTS: Not documented, but likely to be the same as for influenza A subtypes, including sodium hypochlorite (freshly made 1:10 dilution of bleach), 60 to 95% ethanol, 2% alkaline glutaraldehyde, 5 to 8% formalin, 3% lysol, and 5% phenol Footnote 20.
PHYSICAL INACTIVATION: Not documented, but likely to be the same as for influenza A subtypes, including moist heat at 121ºC for 20 minutes or dry heat at 170ºC for 1 hour, 160ºC for 2 hours, or 121ºC for at least 16 hours Footnote 20.
SURVIVAL OUTSIDE HOST: Influenza B virus can survive for 24 to 48 hours on hard, nonporous surfaces such as stainless steel and plastic, and 8 to 12 hours or less on cloth, paper and tissues Footnote 10.
SURVEILLANCE: Monitor for symptoms of influenza Footnote 1. Laboratory confirmation of the virus is not routinely performed but consists of inoculating cell cultures with swabs or washings taken from the nose during the first days of illness. Point-of-care rapid testing, using commercially available diagnostic test kits, may also be performed in order to distinguish between influenza A and B, especially in out-of-season outbreaks Footnote 21.
FIRST AID/TREATMENT: Supportive. Oseltamivir and zanamivir used to treat influenza B viruses Footnote 15, although oseltamivir is deemed to be less effective against influenza B than it is against influenza A Footnote 18. These drugs are not effective against influenza C.
IMMUNIZATION: The most effective strategy for reducing the impact of influenza is through annual vaccination using a live attenuated influenza vaccine (LAIV) or an inactivated influenza vaccine (TIV) Footnote 15. Both LAIV and TIV contain strains of influenza viruses that are antigenically equivalent to the annually recommended strains: 1 influenza A (H3N2) virus, 1 influenza A (H1N1) virus and 1 influenza B virus Footnote 15, Footnote 16. Each year, one or more virus strains might be changed on the basis of global surveillance for influenza viruses and the spread of new strains Footnote 15. LAIV is administered intranasally by sprayer, whereas TIV is administered intramuscularly by injection. LAIV is currently approved only for use among healthy persons aged 5 to 49 years Footnote 15. The current vaccine does not protect against influenza C Footnote 22. LAIV is not available in Canada.
PROPHYLAXIS: Vaccines that protect against influenza B are available Footnote 15, Footnote 16; however, chemoprophylactic drugs must not be overlooked in the control or prevention of influenza. Antiviral prophylaxis must be initiated within 3 days of the detected illness of the index cases to be effective in slowing transmission Footnote 23. Available drugs for prophylaxis are the neuraminidase inhibitors, zanamivir and oseltamivir Footnote 15, Footnote 16.
LABORATORY-ACQUIRED INFECTIONS: Unknown.
SOURCES/SPECIMENS: Respiratory tissues, human secretions, and infected animals Footnote 1.
PRIMARY HAZARDS: Inhalation of virus from aerosols generated when aspirating, dispensing, or mixing virus-infected samples Footnote 1.
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 Footnote 24.
RISK GROUP CLASSIFICATION: Risk Group 2 Footnote 25.
CONTAINMENT REQUIREMENTS: Containment Level 2 practices and containment are required when receiving and inoculating routine diagnostic circulating human specimens Footnote 26; however, additional operational precautions are required to reduce the possibility of direct transmission and re-assortment in humans. Any work involving the intentional co-infection of human and animal influenza viruses in animal models requires a Containment Level 3 facility and operational procedures with rigorous adherence to additional respiratory protection and clothing change protocols Footnote 16.
PROTECTIVE CLOTHING: Wear protective solid-front gowns, gloves and N95 respiratory protection. Manipulations that may produce aerosols should be carried out in a certified biological cabinet Footnote 26.
OTHER PRECAUTIONS: Centrifugation of respiratory and tissue specimens should be carried out using sealed centrifuge cups or rotors, both of which are to be unloaded in a biological safety cabinet Footnote 26.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply 1% sodium hypochlorite, starting at the perimeter and working towards the centre. Allow sufficient contact time (30 minutes) before clean up Footnote 16, Footnote 20.
DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism before disposing by autoclave, chemical disinfection, gamma irradiation, or incineration Footnote 20, Footnote 26.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled. Footnote 26.
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Material Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2011