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Likely Human to Human H5N1 Transmission in Jiangsu China
December 8, 2007
Joanna Brent, a Beijing-based WHO spokeswoman, said the father began presenting symptoms on Monday and was confirmed as having the virus on Wednesday. She said he was being monitored in hospital.
'Because the possibility of human to human transmission cannot be ruled out, we will be monitoring this case closely,' Brent told reporters.
'If it is found to be easily passed between humans, we would be concerned,' Ms Brent said.
Ms Brent said there was no evidence that the man had been infected by his 24-year-old son, who died on Dec 2, but said the possibility could not yet be eliminated.
Ms Brent said it was also possible that both men were infected by the same bird, or that they were infected separately from different sources.
The above comments by WHO offer multiple possibilities for transmission within the Jiangsu cluster, but the transmission is likely to be human-to-human because the son infected his father.
H5N1 clusters give rise to to main possibilities, infection from a common source or human-to-human transmission. These two possibilities are largely decided by the disease onset dates. Since confirmed H5N1 human cases are very rare, it is likely that two infections within one household are linked.
If a common source (bird or human) is involved, both family members will develop symptoms at a similar time. If the index case infects the family member, there will be a gap in the disease onset dates. In this cluster, the son developed symptoms on November 24, while the father developed symptoms on December 3. This gap would make human-to-human transmission likely.
This likelihood is increased because the index case has no known contact with infected poultry, decreasing the likelihood that the father and son were infected by a common source.
This cluster has attracted significant attention in the popular press, in part because of the gap in disease onset dates. However, there are additional reports in the Chinese press indicating the father died on Thursday and the mother and girlfriend of the index case have symptoms. If H5N1 confirmed, the likelihood of human-to-human transmission would increase markedly.
Recombinomics Paper at Nature Precedings