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Familial H7N9 Cluster In Hangzhou Zhejiang
Recombinomics Commentary 14:45
December 10, 2013

The patient became ill on November 20 and was admitted to a local hospital on November 22 for treatment. He is currently in critical condition. His sample tested positive for the avian influenza A(H7N9) virus upon testing by the relevant health authority of Hangzhou.
Yu a November 29 onset, mainly fever, cough, fever immediately to a hospital in Zhejiang outpatient treatment. "After November 27 Moumou confirmed, because the risk of a no symptoms, and no sampling checks. Nov. 29, after he had a fever, we immediately sampling tests, the results were negative until December 5 sicker, the first Secondary test results were positive, he was diagnosed infected with H7N9 avian influenza. "

The above translations describe a Hangzhou (see map) familial cluster involving an index case (57M) who developed symptoms on November 20 and his son-in-law (30M) who developed symptoms on November 29.  The disease onset dates and relationship between the two cases is cited in the WHO December 10 H7N9 update, which also includes the two cases in Hong Kong (36F and 80M).  WHO notes in the update, as well as numerous tweets, that there is no evidence of sustained human to human (H2H) transmission, which is distinctly different from the curious ProMED comments citing no evidence of H2H transmission.

When contacts develop symptoms that have a significant gap in disease onset days (like the 9 days cited above), it is likely that the index case infected the contact, especially when the contact cared for the index case, as happened in Hangzhou, Zhejiang.

A small number of familial clusters were cited in the spring, so familial H7N9 clusters are not new.  However, the cluster in Hangzhou and the linkage of the two cases in Hong Kong to the same hospital (Tuen Mun) has raised concerns that the frequency of such clusters may be on the rise, and the size and number of such clusters may be limited by false negatives.

The above detail on the second case notes that he tested negative when he initially developed symptoms on November 29, and continued to test negative until December 5.  Initial negative results were also reported for the index case in Hong Kong.  The testing protocol in Hong Kong used the rapid test for monitoring, which is then followed by antiviral treatment and additional testing if the patient’s flu-like symptoms worsen.  Thus, milder cases who initially test negative and recover are not lab confirmed, which leads to fewer clusters and a higher case fatality rate, but masks the H2H transmission.

The sequences, A/Hong Kong/5942/2013) from the index case in Hong Kong were released 5 days after collection,  Confirmation of the three other cases cited above were confirmed using samples collected more than five days ago. 

Prompt release of these sequences and more aggressive testing of symptomatic contacts would be useful.

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