Avian influenza A virus infections in humans

Although avian influenza A viruses usually do not infect humans, rare cases of human infection with an avian influenza viruses have been reported since 1996. Since November 2003, more than 330 confirmed cases of human infection with the highly pathogenic avian influenza A (H5N1) virus were reported in 14 countries. The World Health Organization (WHO) maintains situation updates and cumulative reports of human cases of avian influenza A (H5N1). Most human cases of H5N1 infection have occurred during direct contact with sick or dead infected poultry. Another subtype of avian influenza had infected humans, including low pathogenic and highly pathogenic strains. (For more information, see "low pathogenic against Highly Pathogenic Avian Influenza Viruses" on the CDC Influenza Virus Web page.) Most human infections with other avian influenza virus A have also been attributed to direct contact poultry. Human clinical disease from infection with avian influenza A virus ranged from eye infections (conjunctivitis) or severe respiratory disease (pneumonia) death. Because of concerns about the possibility of widespread infection in the human population, public health authorities closely monitor outbreaks of human illness associated with avian influenza. The spread of avian influenza A virus from a sick person to another has been reported very rarely, and it was limited, sporadic and ineffective. But because the avian influenza A viruses have the potential to change and gain the ability to spread easily between people, monitoring of human infection and person-to-person transmission is important. (See information on influenza pandemics for more information.) Cases of avian influenza human infections Confirmed cases of avian influenza A virus infections in humans since 1996 include: * H7N7, the United Kingdom, 1996: An adult conjunctivitis after a piece of straw eye contact with her while cleaning a duck house. Low pathogenicity avian influenza A (H7N7) virus was isolated from a specimen of the conjunctiva. The person was not hospitalized and recovered. * H5N1, in Hong Kong, Special Administrative Region, 1997: Highly Pathogenic Avian Influenza A (H5N1) occurred in the two infections in poultry and humans. It was the first time that an avian influenza virus A transmission of the virus directly from birds to humans was the cause of respiratory ailments. During this outbreak, 18 people were hospitalized and six of them died. To control the outbreak, authorities killed about 1.5 million chickens to remove the source of the virus. The most important risk factor for H5N1 infection of the man was visiting a live poultry market in the week prior to the onset of disease. * H9N2, China and Hong Kong, Special Administrative Region, 1999: Low pathogenic avian influenza A (H9N2) virus infection was confirmed in two hospitalized children and resulted in few signs of influenza-like illness. Both patients recovered, and no additional cases were confirmed. The source is unknown. Several other human infections of the H9N2 virus were reported from China in 1998-99. * H7N2, Virginia, 2002: Following an outbreak of low pathogenic avian influenza A (H7N2) among poultry in the Shenandoah Valley area of poultry production, a person developed a simple flu symptoms and had serological evidence of infection by the H7N2 virus. * H5N1, China and Hong Kong, Special Administrative Region, 2003: Two cases of highly pathogenic avian influenza A (H5N1) virus infection occurred among members of a Hong Kong family that had traveled to China. One person recovered, the other died. How and where these two family members were infected was not determined. Another family member died of a respiratory illness in China, but no testing was done. * H7N7, Netherlands, 2003: The Netherlands reported outbreaks of highly pathogenic avian influenza A (H7N7) virus among poultry on multiple farms. A total of 89 people were confirmed to have H7N7 virus infections associated with outbreaks in poultry. Most human cases have occurred among poultry. H7N7 of the disease has been associated generally mild and included 78 cases of conjunctivitis (eye infection), five cases of conjunctivitis and influenza-like illness with fever, cough and muscle aches; two cases of influenza-like illness, and four cases that were classified under "other". One death occurred in a veterinarian who visited one of the affected farms and developed complications of H7N7 infection, including acute respiratory distress syndrome. The majority of H7N7 cases occurred through direct contact with infected poultry. However, the Dutch authorities reported three possible cases of human-to-human H7N7 virus from poultry workers to family members. * H9N2, in Hong Kong, Special Administrative Region, 2003: Low pathogenic avian influenza A (H9N2) virus infection was confirmed in a child in Hong Kong. The child was hospitalized with a flu-like illness and recovered. * H7N2, New York, 2003: In November 2003, a patient with serious underlying medical was admitted to a hospital in New York with respiratory symptoms. The patient recovered and returned home after a few weeks. Testing revealed that the patient was infected with a low pathogenic avian influenza A (H7N2) virus. * H7N3, Canada, 2004: In March 2004, two poultry workers who helped in culling operations during much influenza A (H7N3) avian outbreak confirmed culture-conjunctivitis, one of whom was also coryza . The two poultry workers recovered. A worker has been infected with the H7N3 low pathogenic and with the highly pathogenic H7N3. * H5N1, Thailand and Vietnam, 2004: In late 2003 and early 2004, severe and fatal human infections with the highly pathogenic avian influenza A (H5N1) have been associated with widespread virus outbreaks poultry. Most cases of pneumonia and had a lot of respiratory failure. Some additional cases of human H5N1 infection have been reported during the mid-2004 and late 2004. Most cases appear to be associated with direct contact with sick or dead poultry. An example of probable limited human-to-human spread of H5N1 virus is suspected to have taken place in Thailand. A total of 50 cases of human H5N1 infection, with 36 deaths have been reported in three countries. * H5N1, Cambodia, China, Indonesia, Thailand and Vietnam, 2005: Serious and fatal human infections with the highly pathogenic avian influenza A (H5N1) have been associated with the virus current H5N1 outbreak in poultry in the region. A total of 98 cases of human H5N1 infection, with 43 deaths were reported from five countries. * H5N1, Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Thailand, Turkey, 2006: serious and fatal human infections with the highly pathogenic avian influenza A (H5N1) viruses are produced in association with the disease and the enlargement process. While most of these cases occurred as a result of contact with infected poultry, Azerbaijan, the most plausible cause of exposure to the H5N1 virus in several cases of human infection is thought to be infected through contact with wild birds dead (swans). The largest family cluster of H5N1 cases have occurred so far in the north of Sumatra, Indonesia in May 2006, with seven cases confirmed H5N1 and a probable case of H5N1, including seven deaths. Overall, 115 cases of human H5N1 infection with 79 deaths have been reported in nine countries. * H5N1, Cambodia, China, Egypt, Indonesia, Laos, Myanmar, Nigeria, Pakistan, Vietnam, 2007: serious and fatal human infections with the highly pathogenic avian influenza A (H5N1) viruses have occurred in association with outbreaks poultry. In addition, during 2007, Nigeria (January), Laos (February), Myanmar (December), and Pakistan (2007) have confirmed their first human infections with the H5N1 virus. * H7N2, the United Kingdom, 2007: human infection with low pathogenic avian influenza A (H7N2) virus causing flu-like illness and conjunctivitis have been identified in four cases hospitalized. These cases have been associated with avian H7N2 outbreak in Wales. * H9N2, China, 2007: In March 2007, in Hong Kong, Special Administrative Region, confirmed low pathogenic avian influenza A (H9N2) infection by the virus 9-month-old daughter slight signs of the disease . The World Health Organization (WHO), the site offers a chronology of the main avian influenza A (H5N1). Symptoms of bird flu in humans The reported symptoms of avian influenza in humans have ranged from eye infections (conjunctivitis) of influenza-like illness symptoms (eg fever, cough, sore throat, muscle aches) to the severe respiratory illness (eg, pneumonia, acute respiratory distress , viral pneumonia) sometimes accompanied by nausea, vomiting and neurological. Antiviral Agents for avian influenza A virus infections in humans The CDC and WHO recommend oseltamivir, an antiviral drug prescription, treatment and chemoprophylaxis of human infection with an avian influenza virus. Analyses of H5N1 virus circulating available worldwide suggest that most viruses are susceptible to oseltamivir. However, some evidence of oseltamivir resistance were reported in the H5N1 virus isolated in some cases of human H5N1 infection. Ongoing monitoring of antiviral resistance among avian influenza virus A is critical. Prevention of avian influenza A virus infections in humans People exposed to avian influenza A-infected infected poultry or potentially is advisable to follow the good practice of infection control, including special attention to hand hygiene, and use personal protective equipment . In addition, they must be vaccinated against seasonal influenza and the flu should take antiviral drugs as a prophylactic. People exposed should be closely monitored for symptoms that develop during the week and after exposure to infected poultry or potentially to avian flu-contaminated environments.
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