Case history #1
A previously healthy 68-year-old Chinese man develops acute-onset fever (body temperature >38.8°C [>102°F]) and fatigue for two days. He had visited a local live poultry market one week before onset of symptoms to buy fresh chicken meat for a meal he prepared for his family. None of his family experience similar symptoms. Over the following two days he remains febrile, and develops a new, productive cough. He becomes increasingly short of breath, so his daughter takes him to the local hospital. A chest radiograph reveals multilobar, patchy lung infiltrates. A full blood count reveals a normal white cell count but lymphopenia, and the platelet count is below the normal range. C-reactive protein, alanine aminotransferase, and aspartate aminotransferase are all found to be elevated. A nasopharyngeal swab collected upon hospitalisation is tested for a panel of influenza and other respiratory viruses. Influenza A(H7N9) virus infection is confirmed by reverse transcription polymerase chain reaction (RT-PCR).
Case history #2
A 45-year-old Chinese-Australian woman with hypertension and diabetes mellitus develops progressive fever, headache, non-productive cough, and shortness of breath on minimal exertion, five days after returning to Australia from central China. She had stayed with relatives in a small city to celebrate Chinese New Year, but had not visited any live poultry markets. Her husband, who did not travel with her, has coryzal symptoms only. On arrival to the emergency department, she is tachypnoeic, tachycardic, and hypotensive, and has oxygen saturations of 90% on room air. She coughs while being assessed and then vomits. Auscultation reveals decreased breath sounds at the base of her left lung. A chest radiograph demonstrates patchy infiltrates in lower zones of both lung fields and a focus of dense consolidation in the right lower lobe. Laboratory findings include leukocytosis, lymphopenia, anaemia, thrombocytosis, and hypoxaemia. C-reactive protein, lactate dehydrogenase, and procalcitonin are all elevated, but the creatine kinase level is normal. She deteriorates rapidly, requiring intubation and mechanical ventilation 8 hours after being admitted to hospital. A computed tomography scan of her thorax is performed, revealing bilateral ground glass changes and dense consolidation of the left lower lobe and a small pleural effusion. Clinical specimens including combined nose and throat swabs and endotracheal aspirates are tested by RT-PCR for a panel of influenza and other respiratory viruses daily. While day 1 specimens test negative for respiratory viruses, the day 2 endotracheal aspirate tests positive for presence of influenza A(H7N9) virus.
Mild influenza-like illness without organ dysfunction has been described, but is uncommon. In the first three months of the 2013 outbreak, a large surveillance system in mainland China assessed patients presenting to outpatient services and emergency departments with influenza-like illness. Asian lineage low-pathogenic avian influenza (LPAI) A(H7N9) virus infection was confirmed in five patients, three of whom had mild illness (fever and upper respiratory tract symptoms) and did not require hospitalisation. Two of the patients were young children and one was a 26-year-old adult. Diarrhoea or vomiting was reported in 14% in one case series, although not as isolated symptoms. Unlike infection with other avian influenza A(H7) viruses, initial conjunctivitis has not been reported. Similar to highly pathogenic avian influenza (HPAI) A(H5N1) and complicated seasonal influenza A(H1N1)pdm09 virus infections, most patients with Asian lineage A(H7N9) virus infection present with symptoms consistent with moderate or severe community-acquired pneumonia.
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