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Dual Bird Flu Infections in Familial Clusters in Thai Binh in 2004
March 10, 2005
>> In January 2004, Vietnam reported a family cluster which involved a 31-year-old man and his two sisters from Thai Binh. The man named Ngo Le Hung, who had handled sick chickens before and after his wedding on Jan. 3, died on Jan. 12. Two of his younger sisters, Ngo Le Hanh and Ngo Le Hong, died on Jan. 23. The two sisters were confirmed to have contracted H5N1. However, no samples of his brother were available for testing.
The genetic sequencing analysis of viruses taken from the two Vietnamese sisters conducted by the WHO showed that there are no possibilities of person-to-person transmission of bird flu. <<
The finding of two distinct sequences in the sisters described above certainly does not rule out human-to-human transmission. Instead it indicates that their brother was dually infected, which would explain some of the unusual clinical presentations as well as the large number of Thai Binh clusters in 2005.
Dual infections with H5N1 are common in poultry. One method that separates the two viruses is isolation in different organs. This "experiment" apparently was done in "nature", but it appears that WHO is so intent on finding data that contradicts clear human-to-human transmission, that their data somehow gets converted into media reports that say there was "no possibility of person-to-person transmission" in this clear-cut transmission at the beginning of 2004.
H5N1 isolates from chickens in Hong Kong in 2001 contained multiple strains of virus. A comparison of the virus isolated from a chicken to an isolate from a mouse brain revealed significant differences between the viruses. The peer reviewed papers concluded that the isolates from chickens were mixtures, but failed to note that they were recombinants.
A similar situation arose with the WSN/33 virus. The original isolate came from a physician in England, Christopher Matthewes, in 1933. The virus was the first human influenza virus isolated, and was called WS/33, named after Wilson Smith, the scientists who isolated the virus. In 1940 the virus was passaged through mouse brains, and two viruses were isolated, WSN/33 and NWS/33. Both viruses were neurotropic and the N was appended to the name to denote that characteristic. Sequencing of the two neurotropic viruses was done several decades later. NWS/33 was sequenced in Australia in the early 90's and WSN/33 was sequenced in the early 80's and 90's in the United States. Sequences for H and N are available for all three isolates. Recently two more H1N1 sequences of WSN-like virus isolated from pigs in Korea were also deposited at GenBank in 2004.
The sequences at GenBank verify the differences among the three isolates. Although all 5 isolates have a few unique polymorphisms, the two H1N1 swine isolates clearly have WSN/33 related sequences. Sequence data is available for all 5 isolates at positions 32-904 of the WSN/33 HA sequence. There are 25 positions that are the same in WS/33 and NWS/33 but different than WSN/33. In 21 of those 25 positions, the two swine isolates match WSN/33. In addition WSN/33 has a 3 bp deletion and the same deletion is in the two swine sequences.
Similarly, sequence data is available for positions 19-1116 of the NA sequence and there are 9 differences between WSN/33 and the other two human isolates. The swine isolates match WSN/33 at all 9 positions. In addition, both WSN/33 and NWS/33 are missing a glycosylation site at position 130 in the NA protein, but WSN/33 changes the N to R while NWS/33 changes the N to Y. Both of the swine sequences match WSN/33, encoding an R at position 130. Thus, the swine sequences confirm the differences between the three isolates even though all three isolates trace back to the same physician in London in 1933. Moreover, these differences can be seen in sequences generated in 2004 and compared to sequences generated 15-25 years earlier.
Thus, there is little doubt that several different viruses can be isolated from the same person, especially when isolated from different tissues. In a recent media report, the mother of the three dead children had commented that she didn't think any of her children had been infected with H5N1 because one of her daughters had a respiratory illness while the other had a gastrointestinal disease.
The WHO comment quoted above would seem to indicate that the two daughters were both infected with H5N1 as indicated in the diagnostic test in 2004. However, since both daughters cared for their brother and both sisters developed symptoms on the same day, entered the hospital on the same day, were initially said to be inconclusive for H5N1, were subsequently found to be H5N1 positive, and died on the same day, it would seem that they were both infected by their brother, who was dually infected with two distinctly different H5N1 viruses that had altered tissue tropisms.
Dual infections can generate recombinants and cause clinically different diseases, which can be complex. There has been evidence for such dual infections since 2004 in Thai Binh, yet such infections are still considered impossible by at least some at the WHO. There is significant cause for concern, especially because of the number of Thai Binh clusters in 2005 and, the proven ability of H5N1 to have different tissue tropisms and produce clinically different diseases.