On May 20, 2013, the Taiwan Centers for Disease Control (Taiwan CDC) received a report from a hospital concerning a case of human infection with unsubtypable influenza A virus in a 20-year-old female presenting mild pneumonia who resides in central Taiwan. The virus isolated from the respiratory specimen from the case was then submitted to Taiwan CDC for further identification. After conducting whole genome sequencing, the National Influenza Center (NIC) at Taiwan CDC identified the virus to be a novel avian-origin influenza A (H6N1) virus. A total of 36 close contacts of the case have been traced for follow-up. 4 of them experienced influenza-like illness symptoms, but none of them has been found to be infected with influenza A (H6N1) virus. Taiwan CDC continues to closely monitor the influenza activity and advises the public to seek immediate medical attention when experiencing any influenza-like illness with respiratory distress.
According to the epidemiological investigation, the case works at a breakfast shop. She had not traveled out of the country and had not been exposed to any poultry or bird. On May 5, she developed symptoms, including fever, cough, headache and muscle ache. On May 8, when her fever persisted and she developed shortness of breath, she sought medical attention at a hospital and was hospitalized for treatment. Her chest X-ray showed mild pneumonia. After administering Oseltamivir, her symptoms improved the next day. On May 11, she was discharged from the hospital. As of now, she has fully recovered. Influenza A (H6N1) virus was isolated from the respiratory specimen collected from the case on May 7. The case was found to have an antibody titer of 1:20 in the serum specimen collected on May 24. Another serum specimen was collected from the case on June 8 and the antibody titer in this specimen was found to be 1:40. Besides testing the respiratory specimen collected from the case for influenza viruses, the NIC also tested the specimen for 23 other common respiratory viruses such as adenovirus, respiratory syncytial virus, coronavirus, enterovirus and rhinovirus and the specimen tested negative for all these viruses. The agricultural authority has collected specimens from the poultry from the two poultry farms located within the 1-km radius of the case’s residence. No avian influenza A (H6N1) virus has been detected in any of the specimens.
Beginning 1999, besides testing specimens from patients with notifiable infectious diseases such as influenza-related complications, Taiwan CDC regularly collects specimens from patients with influenza-like illness in the community and hospitalized patients with pneumonia of unknown origin to test for influenza viruses and systematically monitors the domestic influenza virus activity and the actual clinical situation (patient visits for influenza-like illness). Each year, on average, approximately 10,000 to 20,000 specimens were tested. As of now, an accumulative total of 250,000 specimens have been tested. 86,000 influenza virus strains have been isolated and identified from the specimens. Besides this H6N1 strain and the imported H7N9 strain detected in 2013, no other non-H1/H3 subtypes of influenza A viruses have been detected in humans in Taiwan.
An expert meeting attended by the agricultural authority, related medical experts and veterinary experts was convened to discuss the case. Based on the results of the epidemiological investigation, the case presenting mild pneumonia is a sporadic case and testing of the close contacts of the cases has not yielded any evidence of human-to-human transmission of this virus in the community. Both the health and agricultural authorities will continue to reinforce avian influenza surveillance in humans, poultry and the environment.
Avian influenza A (H6N1) virus is a low-pathogenic avian influenza virus commonly circulating in the domestic bird population and the virus had not been previously detected in humans. The genome sequence of the virus isolated from the case is found to be avian-origin and closely resembles avian influenza A (H6N1) virus in domestic poultry. The virus is also sensitive to influenza antivirals, including Oseltamivir and Zanamivir according to the sequencing data.
To prevent avian-to-human transmission of avian influenza infections, poultry vendors are advised to take personal precautions and the general public to avoid unnecessary direct contact with poultry and birds or their droppings. In addition, the public is also advised to practice good personal hygiene such as washing hands frequently and consuming only thoroughly cooked poultry and eggs to reduce the risk of infection. If influenza-like illness symptoms or conjunctivitis develop, please put on a surgical mask, seek immediate medical attention and inform your doctor of your exposure history to birds/poultry, job contents and travel history. For more information, please call the toll-free Communicable Disease Reporting and Care Hotline, 1922, or 0800-001922 if calling from a cell phone, or visit the Taiwan CDC’s website at http://www.cdc.gov.tw.