Although avian influenza A viruses usually do not infect humans, more than 200 confirmed cases of human infection with avian influenza viruses have been reported since 1997. The World Health Organization (WHO) maintains situation updates and cumulative reports of human cases of avian influenza A (H5N1). Most cases of avian influenza infection in humans are thought to have resulted from direct contact with infected poultry or contaminated surfaces. However, there is still a lot to learn about how different subtypes and strains of avian influenza virus might affect humans.

Because of concerns about the potential for more widespread infection in the human population, public health authorities closely monitor outbreaks of human illness associated with avian influenza. To date, human infections with avian influenza A viruses detected since 1997 have not resulted in sustained human-to-human transmission. However, because influenza A viruses have the potential to change and gain the ability to spread easily between people, monitoring for human infection and person-to-person transmission is important.

Symptoms of Avian Influenza in Humans

The reported symptoms of avian influenza in humans have ranged from typical influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections (conjunctivitis), pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications.

Vaccine

Development of a human vaccine for H5N1 influenza is currently underway, and availability of a safe and effective vaccine is still uncertain at this point.

Antiviral Agents

The effectiveness of different antivirals against H5N1 avian flu has not yet been fully determined. Four influenza antiviral drugs (amantadine, rimantadine, oseltamivir, and zanamivir) are approved by the U.S. Food and Drug Administration for the treatment and prevention of influenza. However, analyses of some of the 2004 H5N1 viruses isolated from poultry and humans in Asia have shown that the viruses are resistant to two of the medications (amantadine and rimantadine). Other antiviral medications are currrently undergoing evaluation to determine their effectiveness against this virus.

Oseltamivir is currently being used for the treatment of patients infected with influenza A H5N1 and is generally effective, although resistance to oseltamivir has been shown in two of eight Vietnamese patients treated with the medication.

In the event of a pandemic, antivirals will be used for treatment of those already infected, which may help stop the virus from spreading. The U.S. government is stockpiling antivirals for this purpose. The supply of antiviral medications is limited, and at this time, antivirals will not likely be used for prophylaxis. It is not recommended that individuals try to keep a stockpile of antivirals.

Laboratory Testing to Detect Human Infections with Avian Influenza A/H5 Viruses

If you have a patient with travel history or who is a contact of someone who has traveled to an area affected by Influenza A H5N1 with symptoms of flu, please call the Communicable Disease Control Section at (603) 271-4496 to report the patient and to request information about specimen collection and specimen transport.

Infection Control

The exact mode of transmission of avian influenza (AI) is not known and continues to be investigated. Given the uncertainty about the exact modes by which AI, including influenza A (H5N1) may first be transmitted between humans, due to the high mortality of the disease, and the possibility that the virus could mutate or reassort at any time into a strain capable of efficient human-to-human transmission, enhanced infection control precautions for patients with suspected or confirmed AI infection appear warranted. 

Updated guidelines, "Avian Influenza, Including Influenza A (H5N1), in Humans: WHO Interim Infection Control Guideline for Health Care Facilities,"were issued onFebruary 9, 2006."  These guidelines can be found on the HHS Pandemic Flu website (http://pandemicflu.gov) in the Health Care Planning section.

The following is a summary of the WHO guideline:

• Standard and droplet precautions should be the minimum level of precautions to be used in all health care facilities when providing care for patients with acute respiratory illness, regardless of whether AI infection is suspected. The most critical elements of these precautions include facial protection (eyes, nose, and mouth) and hand hygiene and these precautions should be prioritized.
• Full barrier precautions, which include standard, contact, and airborne precautions (plus eye protection) should be used, when possible, when providing care for suspected or confirmed AI-infected patients with close patient contact and during aerosol-generating procedures.
• Because some elements of full barrier precautions (particularly those related to airborne precautions) may not be available in all health care facilities, minimal requirements for caring for AI-infected patients should include standard, contact, and droplet precautions (plus eye protection when within 1 meter of patient and for all aerosol-generating procedures). Additional elements should be prioritized and pursued when resources permit.