In recent months, avian influenza viruses have been detected in fowl and poultry in parts of Europe, Asia, and North America, and now, six human cases of H7N9 bird flu have been reported in mainland China and Macau.
Type A viruses of avian influenza, or bird flu, naturally occur in wild birds and water fowl, and can infect a number of different bird species, including farmed poultry. While birds can often carry these viruses in their respiratory and intestinal tracts without illness, the infections are highly contagious among birds and between bird species. Bird flu can be transmitted through shed feces, saliva, and nasal secretions as well as contaminated surfaces, causing mild illness in cases of low pathogenic avian influenza (LPAI) A viruses, and more severe illness in cases of highly pathogenic avian influenza (HPAI) A viruses.
Cases of bird flu seen in humans rarely occur, but humans can acquire it as well, through contact with infected birds or contaminated surfaces. Avian influenza can be transmitted from birds to humans through inhalation or if secretions from infected birds come into contact with an individual’s eyes, mouth, or nose. Symptoms of bird flu in humans are very similar to human influenza symptoms, and, as in birds, can be more severe when it comes to cases of HPAI viruses. Human-to-human transmission of bird flu is also very uncommon, but not impossible, as the influenza viruses can change and evolve over time.
The World Health Organization (WHO) has announced confirmation of human cases of bird flu that were reported by China’s National Health and Family Planning Commission (NHFPC). China notified WHO on December 12 of six cases of human infection with the H7N9 influenza A virus. Those cases all involved men, ranging in age from 32 to 80 years of age, with symptoms having occurred from November 6 to 20 of this year. Of those infected, five reported recent exposures to live poultry, while one reported no such exposure. Chinese health officials noted that four of the cases occurred in Jiangsu province, while one case occurred in Fujian and another in Guangdong. On December 14, the NHFPC reported an additional case of H7N9 bird flu in a 58-year-old man in the Macao Special Administrative Region. Epidemiological investigation revealed that the case was linked to a batch of poultry from Guangdong which tested positive for the H7N9 antigen.
In response to these recent cases, health officials in China and Macao SAR have responded by increasing control and surveillance efforts in the affected regions. Those infected have received enhanced medical care and observation for both themselves and close contacts. In poultry markets, the public health response has included increased surveillance and infection education efforts, along with risk assessments.
According to WHO officials, these recent cases of H7N9 bring the total number of reported human bird flu infections to 807 worldwide since early 2013. Public health officials expect to see additional human cases, although epidemiological and virological evidence indicate that sustained human transmission is unlikely with the H7N9 virus. WHO recommendations for travelers in affected areas include avoiding poultry markets and farms or any potentially contaminated surfaces, and practicing good food and hand hygiene.
