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H7N2 Familial Cluster in Wales England
May 29, 2007
A dozen schoolchildren and two members of staff at Ysgol Henllan primary school near the Corwen farm have been offered courses of anti-flu drug Tamiflu after one of the pupils is thought to have contracted the virus.
The child lives at a neighbouring property to the farm and the staff and pupils receiving treatment had all been in close proximity to the youngster.
The above comments on the H7N2 outbreak fail to capture the confusion regarding the testing of patients and contacts. The student described above, Megan Evans, had symptoms and responded to treatment. An interview with her father, Ian Evans, indicated he was positive and his wife was initially positive, but subsequently tested negative. Moreover, one of Megan's classmates had symptoms, but tested negative.
Thus, in the Evans family, three members either tested positive or had symptoms, suggesting H7N2 was efficiently transmitted from human-to-human. The number of human cases is remarkably high, since only 15 chickens were bought at the market.
The owners of the farm also initially had symptoms, although they too tested negative. A better picture of human H7N2 infections will emerge when convalescent serum is tested for H7 antibodies. However, at this time, the human-to-human spread appears to be quite efficient, comments by government officials notwithstanding.
The inability to reliably test patients with symptoms, or reliably track contacts, is a major cause for concern. Although these initial cases are mild, extensive passage of H7N2 through a naïve human population can lead to genetic alterations that could affect virulence. These concerns are compounded by the inability of the surveillance program to detect H5N1 or H7 in live wild birds and the potential for dual infections in a number of hosts.