Antibody Testing for New York Brother in H5N1 Pakistan Cluster?
Recombinomics Commentary 3:59
December 28, 2007
Yet another brother, who lives on Long Island, N.Y., travelled to Pakistan with his son to attend at least one of the funerals. On their return to the United States they suffered mild respiratory symptoms and consulted their family doctor, who alerted New York State public health authorities.
In early December, the U.S. Centers for Disease Control sent a plane to Albany, N.Y., to collect samples taken from the two. Testing at the CDC's labs in Atlanta confirmed the man and his son were not infected with the virus.
The above comments on the son contradict the State of New York report that indicated the family of the brother from New York was not exposed to the cases in Pakistan. If both father and son flew to Pakistan for the funeral(s), there would have been exposure. The first brother died November 19 and the other fatally infected brother developed symptoms November 21, so if the father and son were in Pakistan for the first funeral, they would have been exposed to the second brother, as well as the source that infected the second brother. Moreover, if they then stayed for the second funeral, they would have been in Pakistan for more than 3 weeks, since they returned to New York on December 5.
Pakistan acknowledged that some relatives did not develop pneumonia because they were receiving Tamiflu prior to collection of samples. It seems likely that both father and son from the US would also be receiving Tamiflu. One or both developed respiratory symptoms, but testing of mild cases frequently generates false negatives.
As noted in the recent reports on the WHO updates, most of the confirmatory test on patients that had previously tested positive in Pakistani labs, tested negative in NAMRU-3’s mobile lab as well as the Mill Hill labs in London.
Thus, negative testing of the New York residents does not preclude infections in Pakistan, since their symptoms were mild, and they were likely taking prophylactic Tamiflu when tested in the US.
WHO had indicated that follow-up antibody testing was planned for the relatives in Pakistan. The same testing should be applied to the relatives who returned to the United States.
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