Efficient H7N2 Transmission To 11 Patients in Wales England
Recombinomics Commentary
May 27, 2007
The outbreak was confirmed at the Conwy smallholding on Thursday
Officials investigating two possible cases of bird flu in north Wales have traced 26 people who may have been in contact with the disease.
Eleven of these people have shown flu-like symptoms, but none has been seriously ill.
Owners Tony Williams and Barbara Cowling, who have tested negative for the virus, called in a vet after their Rhode Island Red chickens began to die.
They bought the chickens at Chelford Market at Macclesfield, Cheshire, some 70 miles (112 km) away, on 7 May.
The second possible case emerged on Saturday about 35 miles (56 km) away, at a farm understood to be on the outskirts of Efailnewydd, near Pwllheli. It has also been linked to the market.
The above comments detail human-to-human transmission of H7N2 in Wales, England and suggest that the tramission is efficient and the number of human cases will grow significantly.
Although the owners of the farm have tested negative, media reports indicate that earlier they had symptoms. Since their expsore may have been as early as May 7, when one of the 15 infected birds died, the owners may have cleared the H7N2 by the time they were tested, which would have been after May 17, when poultry samples were collected for testing.
It is likely that these collections led to the first four confirmed cases. Three of these four had contact with poultry. Two were from northwest England, and one was from Wales. The patient from Wales, or the owners of the farm, likely infected the fourth positive.
Humans were also likely responsible for the next seven positives, which are also in Wales. Thus, of the 11 confirmed cases, 8 were infected by people, not poultry.
These numbers demonstrate efficient human-to-human transmission, because only 26 people have been tested, and some, like the owners, may be false negatives because the PCR test was too late, while others may be false negatives because they were tested too early.
Similarly, people linked to the sellers of the poultry in Macclesfield have not been described, nor have results of the investigation of a second farm in Efailnewydd been released. Moreover, the distance of the two farms from each other, as well as the market in Macclesfield, suggest that additional farms spread over a relatively large region, may also have unreported human and poultry H7N2 infections.
H7 is efficiently transmitted human-to-human. The symptoms are typically mild and including flu-like symptoms and conjunctivitis. In the 2003 outbreak in the Netherlands, it is likely that over 1000 people were infected, based on H7 antibodies in cullers and contacts. In that outbreak there was one fatality.
Widespread infections of humans with H7 are cause for concern. H5N1 has been reported in Scotland, Denmark, Germany, Austria, and France last year (as well as many additional countries in western Europe).
H5N1 is likely to be circulating undetected in the region. H5N1 was reported in Moscow suburbs this year.
More details on the farm and market, as well as sequences from the H7N2 isolates would be useful.
Media sources
Recombinomics Presentations