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Jan B. Wade · #1 (**permalink**) 04-26-2005, 05:39 AM

High Person-to-Person Transmission of Bird Flu Reported

By Jeff Minerd, MedPage Today Staff Writer Reviewed by Robert Jasmer, MD; Assistant Professor of Medicine, University of California, San Francisco January 10, 2005 Also covered by: Wall Street Journal

MedPage Today Action Points

Advise patients of the importance of receiving the yearly flu vaccine, especially for the very young, the elderly, and the immunocompromised.
Educate patients about symptoms of flu versus symptoms of the common cold.

Review
In the spring of 2003, an unprecedented human outbreak of avian H7N7 influenza occurred in the Netherlands. During an extensive outbreak among poultry on commercial farms, 86 poultry workers and 3 people with no poultry contact were infected.

To follow up on the outbreak and the effectiveness of control measures, Dutch researchers surveyed via questionnaire approximately 400 poultry farmers and their families and almost 900 people who were involved in controlling the epidemic.

The researchers also took and analyzed blood samples from 500 of these individuals to determine if they had been infected with the avian flu virus. Additional studies were performed on 62 household contacts of 25 individuals with confirmed avian flu virus infection.

The Dutch investigators were affiliated with the National Institute of Public Health and the Environment in Bilthoven and the Netherlands Institute for Health Services Research in Utrecht. They published their results in Eurosurveillance Weekly, an online science journal. Highlights of these results are as follows:

At least 50% of the people exposed to infected poultry had detectable H7 antibodies. Based on this finding, the researchers estimate that avian influenza A/H7N7 virus infection occurred in at least 1,000 and perhaps as many as 2,000 people.
The seroprevalence of H7 antibodies in people without contact with infected poultry, but with close household contact to an infected poultry worker, was 59%. "This suggests that the population at risk for avian influenza was not limited to those with direct contact to infected poultry, and that person-to-person transmission may have occurred on a large scale," the Dutch team wrote.
Neither poultry farmers nor those engaged in controlling the epidemic complied satisfactorily with preventive measures. Only 6% of farmers reported consistent use of facial masks and 1% reported consistent use of goggles while working with infected poultry. In those helping to control the epidemic, compliance was only slightly better: 25% consistently used facial masks and 13% used goggles.

The researchers noted that the H7N7 virus causes milder disease than the avian H5N1 influenza virus that killed six people during a Hong Kong outbreak in 1997 but did not spread efficiently from person-to-person. "Both avian influenza outbreaks illustrate that crossing the species barrier is less rare than previously recognised, that avian influenza virus adaptation occurs rapidly, and that if such jumps between species occur, human behaviour in the broad sense may accelerate dissemination," the researchers warned.

Primary source: Final analysis of Netherlands avian influenza outbreaks reveals much higher levels of transmission to humans than previously thought
Source reference:
Bosman A et al. Final analysis of Netherlands avian influenza outbreaks reveals much higher levels of transmission to humans than previously thought. Eurosurveillance Weekly. 2005; 10(1). Accessed January 10, 2005.