Avian influenza outbreak reported in the Netherlands population

This is the third time in the last six years that an avian influenza strain has been known to jump the species barrier and cause illness in humans.

GENEVA — A highly pathogenic strain of avian influenza A virus (H7N7) has caused at least one death and at least 80 minor illnesses in patients in the Netherlands, according to the World Health Organization (WHO).

Several outbreaks of the avian influenza strain at poultry farms were reported to Dutch health officials since February and the strain has also been spotted in Belgium.

Avian strains usually affect poultry exclusively, but the H7N7 strain jumped the species barrier, infecting a 57-year-old veterinarian who visited the farm and later died as a result of the strain. Influenza A (H7N7) was isolated from the patient, and no other respiratory pathogens were detected in a series of laboratory tests, according to a WHO report.

Human illness

This is the third time in the last six years that an avian influenza strain has been known to cause illness in humans. In 1997, an outbreak of influenza A (H5N1) led to 18 cases and six deaths in Hong Kong. In mid-February of this year, the H5N1 strain resurfaced, infecting two people and causing one death.

There has been no direct evidence of human-to-human transmission in its severe form, but an epidemiological investigation has revealed a possible chain of transmission of the disease in milder forms. Three family members of two poultry workers fell ill with a minor respiratory disease and/or minor conjunctivitis, the WHO report said.

Since the beginning of the H7N7 outbreak in the Netherlands in late February, there have been 83 confirmed cases of human H7N7. Most cases (n=79) exhibited conjunctivitis, and 13 of them displayed mild influenza-like illness.

Affected poultry in the Netherlands are being slaughtered as a control measure. Mass culling of poultry proved effective in both Hong Kong outbreaks in preventing further cases in humans.

In accordance with WHO’s pandemic preparedness plan for influenza, the organization is calling for enhanced surveillance and diagnosis of the avian H7N7 virus in humans and susceptible animals, including chickens and pigs.

Health officials in concerned countries should also initiate specific investigations to increase understanding of possible transmission patterns, WHO said. National authorities in the Netherlands and in Belgium have also recommended specific personal protection, such as prophylactic use of the antiviral drug oseltamivir (Tamiflu, Roche) for agricultural workers in contact with H7N7-affected poultry.

WHO advises that people in contact with H7N7-affected poultry flocks should be on guard for any signs and symptoms of respiratory disease. If symptoms arise, they should consult a doctor, who will then initiate laboratory testing and reporting to health officials.

WHO emphasizes that these heightened surveillance measures will help in the timely detection of any further transmission of H7N7 to humans and to prevent its possible spread.

The WHO Global Influenza Surveillance Network is assembling a test kit for H7N7 that will be ready for use in the next month or so. As a precaution, the network is also working on the development of a vaccine for H7N7.