H7N7 is a subtype of Influenzavirus A, a genus of Orthomyxovirus, the viruses responsible for influenza. Highly pathogenic strains (HPAI) and low pathogenic strains (LPAI) exist. H7N7 can infect humans, birds, pigs, seals, and horses in the wild; and has infected mice in laboratory studies. This unusual zoonotic potential represents a pandemic threat. The pandemic threat of influenza H7N7 Hemagglutinin (HA) proteins and HA antibodies were the main research tools for this influenza pandemic threat.
On 28 February 2003, the highly pathogenic avian influenza A virus subtype H7N7 (HPAI A/H7N7) was isolated for the first time in the Netherlands from poultry on a farm, identifying the start of a large epizootic that also affected Germany and Belgium. In the Netherlands, infected poultry on 255 farms were culled, as well as poultry on 1094 surrounding farms, resulting in the killing of more than 30 million chickens. What's more, in 2003 in the Netherlands 89 people were confirmed to have the H7N7 influenza virus infection following an outbreak in poultry on several farms. One death was recorded. Final analysis of Dutch avian influenza outbreaks reveals much higher levels of transmission to humans than previously thought.
In August 2006, low pathogenic (LP) H7N7 was found during routine testing at a poultry farm in Voorthuizen in the central Netherlands. As a precautionary measure, 25,000 chickens were culled from Voorthuizen and surrounding farms.
In June 2008, high pathogenic (HP) H7N7 was confirmed on a 25,000-bird laying unit at Shenington, England; probably derived from a pre-existing low pathogenic variety. "Increased mortality (2.5 per cent in one shed) and a drop in egg production had been recorded two weeks before birds started dying in large numbers on June 2, leading to the diagnosis of HP H7N7 on June 4."
In October 2009, high pathogenic (HP) H7N7 was confirmed on a farm in Almoguera, Guadalajara, Spain. Hong Kong announced that it would suspend the import of poultry from Spain.