Efficient Bird Flu Transmission in Thai Binh Vietnam
Recombinomics Commentary
March 7, 2005
>> Most bird-flu victims are thought to have caught the virus from contact with poultry, and infections among health-care workers or patients' family members would raise suspicion that human-to-human virus transmission has taken place, a WHO report said in January. The man's case, if confirmed, would be the first known instance of bird flu in a health-care worker, said Peter Cordingley, a WHO spokesman based in Manila.
``Any case in a health-care worker draws particular attention, and we'll be watching this carefully,'' said Cordingley, in a telephone interview from Manila. ``On the basis of the accounts we've seen so far, it's way too early to draw any conclusions.''
Vietnamese health officials said the cause of the man's infection isn't known, and indicated that he may have also had potential exposure to infected poultry. The nurse carried a 21- year-old bird flu patient on a stretcher and provided direct treatment at the Thai Thuy District Health-Care Center, said Dao Trong Bich, deputy director of the center. The patient was later transferred to a hospital in Hanoi and is in critical condition.
``The reason concerning why this nurse contracted the virus has not yet been determined,'' said Diu. ``But according to the preliminary investigation, he has a girlfriend in a village where bird-flu is present, and he went to her house and had meals there during Tet,'' the Vietnamese New Year that was celebrated last month. <<
The evidence for human-to-human transmission of H5N1 in Thai Binh province is overwhelming. There have been 11 reported familial clusters in Vietnam, Thailand, and Cambodia and all 11 have been bimodal for disease onset dates. Bimodal distributions strongly implicate human-to-human transmission in individual clusters. 2 or 3 such clusters would make human-to-human transmission of bird flu very likely. 11 of 11 is overwhelming evidence of transmission from one family member to another.
For Thai Binh, the data is even stronger because there is a clustering of the familial clusters. 3 of the 11 clusters have been in Thai Binh. Moreover, there has also been geographical clustering of the non-familial cases. The last 8 confirmed or suspect cases have been from northern Vietnam and five of the eight have been from Thai Binh. Vietnam has declared Thai Binh H5N1 free since Feb 5 and the latest OIE report shows a very small number of infected chickens or ducks in Thai Binh.
The H5N1 positive health care worker, who helped carry the stretcher of one of the most critical H5N1 patients, provides strong support for efficient human-to-human transmission. There has been no data supporting transmission from meals. Details of the meals, showing others who developed no symptoms of evidence of disease, coupled with disease onset dates, and bimodal distributions strongly discount common sources, including meals.
The casual contact, between the health care worker and the H5N1 positive patient, is clearly a cause for concern.
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