Influenza Agent Information Sheet

Boston University
Research Occupational Health Program (ROHP)
617-358-7647

Agent

Influenza virus is a segmented negative-sense RNA virus, which belongs to influenzavirus genus in the Orthomyxoviridae family. The virus particle is 80-120 nm in diameter and consists of a central RNA core wrapped by two large glycoproteins (Hemagglutinin or HA and neuraminidase or NA) within an envelope.  These HA and NA glycoproteins are the virulence factors responsible for causing infectious disease.

There are four genera of influenza virus that infect vertebrates: influenza virus A, B, C, and D. Influenza A has the most diverse subtypes and highest concern due to its zoonotic and pandemic potential.

Influenza A and B viruses cause seasonal flu epidemics in humans. Influenza A subtypes like H5N1 primarily infect birds, but infections in mammals, including humans, are also documented.

Disease/Infection

The Seasonal Influenza virus may cause influenza or the “flu”, a contagious respiratory illness.  It can cause mild to severe illness, and at times can lead to death due to pulmonary complications.

The Avian Influenza (H5N1) is a highly pathogenic avian influenza. While it primarily infects birds, it can cause severe contagious respiratory illness that is often fatal in humans, when transmission occurs.

Pathogenicity

Three genera or types predominate: A, B, and C.  New subtypes or strains of influenza can result from re-assortment of human and avian influenza virus genes (antigenic shift) and have the potential to result in epidemics or pandemics.  Antigenic changes within a type or subtype (antigenic drift) of A and B viruses are ongoing processes that are responsible for frequent epidemics and regional and seasonal outbreaks and make the annual reformulation of influenza vaccine necessary.  The morbidity and mortality from influenza is dependent on the strain and on the host.

• Special Populations at Risk:
  Pregnant women, young children, the elderly, those with compromised immune systems, or the chronically ill are at a greater risk of developing complications, and experience more severe illness.
• Other Special Populations at Risk with Avian Influenza (H5N1):
  Poultry workers and farmers and those working with live animals such as veterinarians, bird handlers, and those working with cattle are at a greater risk of contracting the virus due to direct exposure.

Biosafety Information

Risk Group/BSL
Risk Group 2:  Seasonal Influenza virus
Biosafety level:  BSL2/ABSL2

Risk Group 3:  Avian Influenza (H5N1)
Biosafety level:  BSL3/ABSL3

Modes of Transmission

Seasonal Influenza

Avian Influenza (H5N1)

Host Range/Reservoir
Seasonal Influenza A and B viruses circulate widely among humans.

Avian Influenza(H5N1) is found in different wild animals, including wild aquatic birds (ducks, geese, swans, shorebirds), domestic poultry (chickens and turkeys), cattle, pigs, horses, dogs, and cats. Avian Influenza(H5N1) has also been found in humans.

Symptoms
Seasonal Influenza: Symptoms vary but consist of an acute viral disease of the respiratory tract, fever, headache, lack of energy, myalgia, sore throat, cough, nasal congestion, and possibly runny nose.  In rare cases myositis or rhabdomyolysis (muscle inflammation), cardiac, GI symptoms, and central nervous system manifestations have also been reported.  Many patients with influenza pneumonia may also be at risk for secondary bacterial pneumonia.

Avian Influenza (H5N1): Symptoms vary but consist of eye symptoms such as conjunctivitis, fever (but not always present), cough, sore throat, runny nose, muscle or body aches, headaches, fatigue. Less common symptoms are diarrhea, nausea, and vomiting. Complications can include pneumonia, respiratory distress/failure, multi-organ failure, sepsis, and inflammation of the brain.

Incubation Period
Seasonal Influenza: The incubation period is typically 2 days but ranges from 1-4 days after exposure.

Avian Influenza(H5N1): The incubation period is usually 2-7 days after exposure. Respiratory symptoms typically begin about 3 days after exposure, eye symptoms such as redness and irritation can occur 1-2 days after exposure.   

Viability
Seasonal Influenza is killed by heat above 167°F (75°C) and susceptible to disinfectant products containing chlorine, hydrogen peroxide, detergents (soaps), iodophors (iodine-based antiseptics), and alcohols.  Sterilization of reusable instruments and decontamination of surfaces should be performed in accordance with recommendations described by the CDC (www.cdc.gov) and the WHO infection control guidelines (www.who.int/en/).

Avian Influenza (H5N1) is killed by varying temperatures, and is still being studied, but has been noted to range from above 145.4°F (63°C) to 161.6°F (72°C). This virus is susceptible to the same disinfectant products above, as other seasonal influenza viruses. Sterilization of reusable instruments and decontamination of surfaces should also be performed in accordance with recommendations described by the CDC (www.cdc.gov) and the WHO infection control guidelines (www.who.int/en/).

Survival Outside Host

Seasonal Influenza viruses are capable of surviving on hard surfaces for up to 24-48 hours and on tissues for only 15 minutes.  Influenza can remain on the unwashed fingertips for up to 30 minutes and cause indirect transmission.  Good hand hygiene is recommended.

Avian Influenza(H5N1) viruses are capable of surviving outside the host based on varying environment conditions. They can persist in soil and water and remain infectious for long periods. They are known to survive approximately 5 hours on skin and 24 hours on clothing, 7 days in bird feces, 18 days in soil, and up to 21 days in water.

Information for Lab Workers

Laboratory PPE

Seasonal Influenza PPE in lab should include lab coat, gloves, and eye protection when direct skin contact with infected materials or animals is unavoidable.  Eye protection must be used when there is a known or potential risk of exposure to splashes.  Extreme care must be taken to avoid accidental autoinoculation or other parenteral inoculations of infectious tissues and fluids.

Avian Influenza (H1N5) PPE in lab should include BSL3 required PPE to align with CDC recommendations for high-risk exposures to include PAPR, disposable coveralls with fluid resistant gown or apron over this, disposable gloves with optional outer work gloves, and shoe covers. Extreme care must be taken to avoid accidental autoinoculation or other parenteral inoculations of infectious tissues and fluids.

For work outside of BSL3 containment, PPE should be worn when in direct or close contact with sick or dead animals including poultry, wild birds, cattle, other animals, animal feces, or materials potentially contaminated with avian influenza (H5N1).  PPE should include safety goggles, disposable gloves, boots or boot covers, disposable fluid-resistant coveralls, and disposable head cover or hair cover. Respiratory protection should include a NIOSH approved particulate respirator, such as N95, however if not available, a well-fitting surgical mask can be worn. Please contact ROHP for respiratory clearance for N95.

Containment

Seasonal Influenza: BSL-2 practices, containment equipment, and facilities are recommended for activities using clinical materials and diagnostic quantities of infectious material.

Avian Influenza (H5N1): BSL-3 practices, containment equipment, and facilities are recommended for activities using clinical materials and diagnostic quantities of infectious material.

In Case of Exposure/Disease

• For injuries in the lab which are major medical emergencies (heart attacks, seizures, etc…):
  • Medical Campus: call or have a coworker call the Control Center at 617-358–4144.
  • Charles River Campus: call or have a coworker call campus security at 617-353-2121.
    You will be referred to or transported to the appropriate health care location by the emergency response team.
• For lab exposures (needle sticks, bite, cut, scratch, splash, etc…) involving animals or infectious agents, or for unexplained symptoms or illness call the ROHP 24/7 hour number (1-617-358-ROHP (7647); or, 8-ROHP (7647) if calling from an on-campus location) to be connected with the BU Research Occupational Health Program (ROHP) medical officer. ROHP will refer you to the appropriate health care location.
• Under any of these scenarios, always inform the physician of your work in the laboratory and the agent(s) that you work with.
• Provide the wallet-size agent ID card to the physician.

Vaccination

An annual seasonal influenza vaccination is the best way to protect oneself from influenza.  Antibodies develop in the body approximately two weeks after vaccination.

The seasonal flu vaccine will not protect against avian influenza (H5N1). However, people with high-risk occupational exposure to avian influenza (H5N1) or infected animals, should get a seasonal flu vaccine to help protect against seasonal flu and reduce potential for co-infections.

Information for First Responders/Medical Personnel

Public Health Issues

Seasonal influenza is highly spread from person to person primarily through respiratory droplets in the air and with indirect contact transmission. People are most contagious during the first three days of their illness. Standard precautions and droplet precautions should be utilized when caring for individuals with suspected or confirmed influenza for 7 days after illness onset or until 24 hours after the resolution of fever and respiratory symptoms, whichever is longer. Report clusters of influenza-like-illness to Massachusetts Department of Public Health via the online report form or by phone (617) 983-6800.

Avian influenza(H5N1) is widespread in wild birds worldwide and is causing outbreaks in poultry and U.S dairy cows. There is no evidence of sustained human-to-human H5N1 virus transmission in any country. The CDC believes the current risk to the public is low, some people (e.g. those with occupational exposure to the virus or animals that are infected or presumed infected) are at greater risk of infection.  Call the Massachusetts Department of Public Health Epidemiology Program at 617-983-6800 within 24 hours of suspicion or diagnosis and the local board of health (BPHC) where the diagnosis was made.

• After exposure: Immediately after an exposure, the lab worker is not considered infectious. They can be cared for with standard PPE. If after risk assessment is done, the lab worker is determined to be exposed to avian influenza(H5N1), they should monitor themselves for new respiratory illness symptoms, and/or conjunctivitis, for 10 days after their last exposure.
• In case of (suspected) illness: Symptomatic individuals should isolate away from others, including household members, until it is determined that they do not have avian influenza(H5N1) infection.

Diagnosis/Surveillance

Seasonal Influenza: Monitor for clinical signs.  Influenza can be diagnosed with rapid influenza diagnostic tests or rapid molecular assays from a nose or throat swab within 10-20 minutes.

Avian Influenza(H5N1): Monitor for clinical signs. If a patient has influenza-like symptoms, they should first be tested for seasonal influenza. If a symptomatic patient has high risk exposure, the sample should also be sent to a public health laboratory for avian influenza(H5N1) specific PCR testing. The CDC recommends avian influenza(H5N1) specific testing in individuals who exhibit influenza-like illness and/or conjunctivitis with high-risk exposure.

First Aid/Post Exposure Prophylaxis

Perform one of the following actions:

Then call ROHP for prophylaxis for splash or mucus membrane exposure:

1.  First line: Oseltamivir (NA inhibitor), 75 mg, daily for 7 days
2.  Second line if Oseltamivir is not available: Balaxovir 40mg daily for 5 days
3.  If seasonal influenza vaccine was not received, influenza vaccination will be offered

Treatment

Seasonal Influenza: Care is mainly supportive since most illnesses are mild.  On a case-by-case basis, high risk groups or severe illness may be treated with antiviral drugs to prevent complications and shorten the period of illness.  Patients should practice respiratory etiquette and good hand hygiene to limit the transmission of the disease to others.

Avian Influenza(H5N1): Care is focused on administering antiviral treatment ASAP for all confirmed human cases of avian influenza, as well as probable and suspected cases for those with high-risk exposure. Treatment should not be delayed for laboratory confirmation of avian influenza virus infection. The CDC recommends the use of Oseltamivir because this medication has the most human data to support its use compared to other flu antivirals. Supportive care of symptoms is also important and referral for further evaluation in higher acuity healthcare settings, if complications are suspected, as needed.

1.  First line: Oseltamivir (NA inhibitor), 75 mg, BID for 5 days
2.  Second line if Oseltamivir is not available: Balaxovir 40mg daily for 5 days

References

Biosafety in Microbiological and Biomedical Laboratories; Deborah E. Wilson, DrPH, CBSP Director Division of Occupational Health and Safety National Institutes of Health Bethesda, Maryland L. Casey Chosewood, M.D. Director Office of Health and Safety Centers for Disease Control and Prevention Atlanta, Georgia; US Government Printing Office, Washington DC.  5^th Edition; 2007

Control of Communicable Diseases Manual. David L. Heymann. Washington DC, USA: American Public Health Association Press, 19th edition, 2008

Interim Guidance for State and Local Health Depart ments for Reporting Influenza-Associated Hospitalizations and Deaths for the 2009-2010 Season http://www.cdc.gov/H1N1flu/hospitalreporting.htm 

HHS Pandemic Influenza Plan Supplement 2 Laboratory Diagnostics; https://www.cdc.gov/flu/pdf/professionals/hhspandemicinfluenzaplan.pdf

Survival of influenza virus on human fingers Y Thomas et al Clinical Microbiology and Infection 2014; 20; O58-O64

Canadian Food Inspection Agency. (2024). Survival time of avian influenza viruses –inspection.canada.ca. Canada.ca. https://inspection.canada.ca/en/animal-health/terrestrial-animals/diseases/reportable/avian-influenza/survival-time-avian-influenza-viruses

CDC. (2024). Types of Influenza Viruses. Influenza (Flu). https://www.cdc.gov/flu/about/viruses-types.html

CDC. (2024). Avian Influenza Type A. Avian Influenza (Bird Flu). https://www.cdc.gov/bird-flu/about/avian-influenza-type-a.html

CDC. (2024). Signs and Symptoms of Bird Flu in People. Avian Influenza (Bird Flu). https://www.cdc.gov/bird-flu/signs-symptoms/index.html

CDC. Treatment of bird flu. (2025, May 2). Avian Influenza (Bird Flu). https://www.cdc.gov/bird-flu/treatment/index.html

CDC. (2025, July 24). Recommendations for Monitoring and Testing of Individuals Exposed to A(H5N1) Viruses. Avian Influenza (Bird Flu). https://www.cdc.gov/bird-flu/php/surveillance/index.html

Reporting influenza clusters. (2025). Mass.gov. https://www.mass.gov/info-details/reporting-influenza-clusters

Laboratory testing of highly pathogenic avian influenza A(H5N1). (n.d.). https://www.aphl.org/programs/infectious_disease/influenza/Documents/APHL-ASM_Laboratory_Testing_Avian_Influenza_FAQ_2024.pdf

Nuwarda RF, Alharbi AA, Kayser V. An Overview of Influenza Viruses and Vaccines. Vaccines (Basel). 2021 Sep 17;9(9):1032. doi: 10.3390/vaccines9091032. PMID: 34579269; PMCID: PMC8473132.

Ontario Agency for Health Protection and Promotion (Public Health Ontario). Rapid review: Thermal inactivation of influenza A(H5N1) in meat. Toronto, ON: King’s Printer for Ontario; 2024

World Health Organization. (2025). Influenza (seasonal). World Health Organization: WHO. https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal)

World Health Organization. (2023). Influenza (Avian and other zoonotic). Who.int; World Health Organization: WHO. https://www.who.int/news-room/fact-sheets/detail/influenza-(avian-and-other-zoonotic)

Rev. 8/22/25