Apr 3, 2008 (CIDRAP News) – The World Health Organization (WHO) today confirmed two more cases of H5N1 avian influenza from a family cluster that surfaced in Pakistan last fall, supporting the previous finding that the virus probably spread among four brothers but went no further.
Serologic (antibody) testing confirmed that two brothers, one of whom died and the other survived, had the virus, the WHO reported. In addition, the agency said another brother who died had a probable case, but no samples from him were available for testing. The WHO had confirmed one case—Pakistan's first known H5N1 infection—in late December.
The four cases were among at least eight suspected cases in northern Pakistan that were first widely reported Dec 16. The other suspected cases have since been ruled out, according to WHO spokesman Gregory Hartl.
The Pakistan cluster had raised fears that the virus was improving its ability to infect humans, but the WHO said after an initial investigation in December that there was no evidence of sustained person-to-person transmission.
Today the agency stated, "These laboratory test results support the epidemiological findings from the outbreak investigation in December 2007, and the final risk assessment that suggested limited human to human transmission events reported previously. This outbreak did not extend into the community, and appropriate steps were taken to reduce future risks of human infections."
The tests were conducted by the WHO's H5 reference lab in Egypt (US Naval Medical Research Unit 3) and at the US Centers for Disease Control and Prevention in Atlanta.
Cases started with culler
One of the two cases confirmed today was in a man who was previously identified as a veterinarian and had helped cull chickens in an avian flu outbreak area. He became ill on Oct 29 and later recovered, the WHO said.
The other three brothers all fell ill after having close contact with the veterinarian, and none of them had had contact with sick or dead poultry, the agency reported. The second brother in the cluster—whose case is listed as probable—became ill on Nov 12 and died a week later. The other two brothers both got sick on Nov 21; one of them died Nov 28, but the other fully recovered. Officials previously said the brothers helped care for one another during their illnesses.
The man who died Nov 28, listed as the third patient, is the one whose case was confirmed in December. He was identified as a 25-year-old from the Peshawar area. Polymerase chain reaction was used to verify his case.
Serologic tests were used to confirm the two latest cases because no respiratory samples were available, Hartl confirmed today. Explaining why the results were delayed, he told CIDRAP News via e-mail, "Serology takes awhile because the virus has to be grown in sufficient quantity to perform [the] test with sera."
Hartl said the virus in the third Pakistani patient was identified as a clade 2.2 strain of H5N1. Clade 2.2 viruses have been found in birds in more than 60 countries in Asia, Europe, the Middle East, and Africa, and have caused human cases in Azerbaijan, China, Egypt, Djibouti, Iraq, Nigeria, and Turkey, as well as Pakistan, according to a recent WHO report.
The cases in Pakistan sparked concern in the United States after another brother of the infected men, a man living on Long Island, attended the funeral of one of the victims. After his return home, he reported possible exposure to the virus and went into voluntary home quarantine. He was tested and found to be free of the virus.
Latest Indonesian cases confirmed
Yesterday the WHO recognized the three human H5N1 cases—two of them fatal—reported earlier this week by authorities in Indonesia. The agency said the cases, which have not been linked epidemiologically, involve:
- A 15-year-old boy from Subang district, West Java province, who fell ill Mar 19 and died Mar 26
- An 11-year-old girl from Bekasi in West Java who got sick Mar 19 and died Mar 28
- A 21-month-old girl from Bukit Tinggi in West Sumatra; she became ill Mar 17, was hospitalized Mar 22, and is currently recovering.
Indonesia has had 132 confirmed H5N1 cases, of which 107 were fatal, the WHO said.
With the addition of the two Pakistan cases and the three in Indonesia, the WHO's global H5N1 count has risen to 378 cases with 238 deaths.
Apr 3 WHO statement
Jan 3, 2008, CIDRAP News story "WHO: initial analysis of Pakistani H5N1 suggests no dangerous mutations"
Dec 27, 2007, CIDRAP News story "WHO confirms H5N1 case in Pakistan cluster"
Dec 17, 2007, CIDRAP News story "Possible H5N1 family cluster probed in Pakistan"
Apr 2 WHO statement on Indonesian H5N1 cases
February 2008 WHO report "Antigenic and genetic characteristics of H5N1 viruses and candidate H5N1 vaccine viruses developed for potential use as human vaccines"