Transmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands.
BACKGROUND
An outbreak of highly pathogenic avian influenza A virus subtype H7N7 started at the end of February, 2003, in commercial poultry farms in the Netherlands. Although the risk of transmission of these viruses to humans was initially thought to be low, an outbreak investigation was launched to assess the extent of transmission of influenza A virus subtype H7N7 from chickens to humans.


METHODS
All workers in poultry farms, poultry farmers, and their families were asked to report signs of conjunctivitis or influenza-like illness. People with complaints were tested for influenza virus type A subtype H7 (A/H7) infection and completed a health questionnaire about type of symptoms, duration of illness, and possible exposures to infected poultry.


RESULTS
453 people had health complaints--349 reported conjunctivitis, 90 had influenza-like illness, and 67 had other complaints. We detected A/H7 in conjunctival samples from 78 (26.4%) people with conjunctivitis only, in five (9.4%) with influenza-like illness and conjunctivitis, in two (5.4%) with influenza-like illness only, and in four (6%) who reported other symptoms. Most positive samples had been collected within 5 days of symptom onset. A/H7 infection was confirmed in three contacts (of 83 tested), one of whom developed influenza-like illness. Six people had influenza A/H3N2 infection. After 19 people had been diagnosed with the infection, all workers received mandatory influenza virus vaccination and prophylactic treatment with oseltamivir. More than half (56%) of A/H7 infections reported here arose before the vaccination and treatment programme.


CONCLUSIONS
We noted an unexpectedly high number of transmissions of avian influenza A virus subtype H7N7 to people directly involved in handling infected poultry, and we noted evidence for person-to-person transmission. Our data emphasise the importance of adequate surveillance, outbreak preparedness, and pandemic planning.
Diagnostic Laboratory for Infectious Diseases and Perinatal Screening, National Institute of Public Health and the Environment, Bilthoven, Netherlands. marion.koopmans@rivm.nl
Marion
M
Koopmans
Berry
B
Wilbrink
Marina
M
Conyn
Gerard
G
Natrop
Hans
H
van der Nat
Harry
H
Vennema
Adam
A
Meijer
Jim
J
van Steenbergen
Ron
R
Fouchier
Albert
A
Osterhaus
Arnold
A
Bosman
D000293:Adolescent; D000328:Adult; D000382:Agricultural Workers' Diseases / Q000453:epidemiology / Q000821:virology; D000818:Animals; D003236:Conjunctivitis, Viral / Q000453:epidemiology / Q000635:transmission / Q000821:virology; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D053126:Influenza A Virus, H7N7 Subtype; D009980:Influenza A virus / Q000302:isolation & purification; D005585:Influenza in Birds / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D007251:Influenza, Human / Q000635:transmission* / Q000662:veterinary / Q000821:virology; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011200:Poultry; D015047:Zoonoses / Q000453:epidemiology / Q000635:transmission*