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Human-to-human transmission of avian influenza detected
Two clusters studied for avian influenza illness; association made for cases in Indonesia but not in Turkey.
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Evidence of human-to-human transmission of H5N1 was found in an extended family in Indonesia, according to a recent study.
Clusters of highly pathogenic avian influenza (HPAI) illnesses were examined in Indonesia and Turkey. Both clusters involved outbreaks following large family gatherings.
Researchers from the University of Washington and the Fred Hutchinson Cancer Research Center, both in Seattle, analyzed data from two of the largest family clusters to determine if human-to-human transmission occurred and the transmissibility of the strain involved.
The study appeared in Emerging Infectious Diseases.
Indonesia cases
A cluster of eight HPAI cases was detected in the north of the Indonesian island of Sumatra in late April and early May 2006. All patients, excluding the index patient, were confirmed as H5N1 positive. A 37-year-old woman who had been exposed to dead poultry and chicken feces was the index case. Her illness was not confirmed as H5N1. But because of her symptoms, the illness progression and her contact with diseased or dead poultry, experts believe her death was caused by HPAI infection.
Contact with the index case included a family gathering in late April in which 20 members of the extended family attended. The woman was symptomatic at that time and slept in the same room with nine family members after the gathering. Two members died and one became ill.
Of the remaining family 11 family members, four later died. Family members who cared for ill family members also became ill. The possibility that HPAI was transmitted from at least one caregiver case was supported by genetic sequencing data, researchers said. Significant statistical data supported human-to-human transmission.
Cluster in Turkey examined
From Dec. 18, 2005 to Jan. 15, 2006, a cluster of eight H5N1 cases were confirmed in patients in Dogubayazit district in Eastern Turkey. Four people in the cluster died while four recovered. Ten people were hospitalized with avian influenza-like symptoms. Case patients were among 21 members from three households. All had attended a dinner hosted by the family of the index cases. All patients were hospitalized at symptom onset. Researchers did not reject a human-to-human transmission hypothesis, but did not find significant statistical data to support probability of infection from a human source. – by Kirsten H. Ellis
For more information:
- Yang Y, Halloran E, Sugmoto J, Longini Jr. I. Detecting human to human transmission of avian influenza A (H5N1). Emerg Infect Dis. 2007;13:1348-1353.