Curious ProMED Comments On H7N9 Human Transmission
December 8, 2013
It remains uncertain whether the 2nd (imported) case in Hong Kong contracted H7N9 virus infection before or after arrival in Hong Kong. Clarification is awaited. In both of the new H7N9 cases described above, there is no evidence of human-to-human transmission of infection….
The above comments from a ProMED H7N9 update on the two most recent cases (80M in Hong Kong and 30M in Hangzhou) are curious. The above Hong Kong case (80M) developed symptoms three days after admission to Tuen Mun Hospital (TMH), supporting nosocomial transmission, which is further supported by the earlier admission of the first confirmed H7N9 case (36F) in Hong Kong, who was also treated at TMH (which is midway between Palatial Coast home of the family served by the index case and Shenzhen – see map). There has been no evidence of exposure to H7N9 poultry in chickens in Shenzhen, but the family served by the index case was symptomatic, and both confirmed H7N9 cases in Hong Kong were treated at TMH.
Similarly, the only known H7N9 exposure of the most recent case (30M) in Hangzhou, Zhejiang is his father-in-law (57M), who has been H7N9 confirmed. The gap in hospitalization dates suggests the younger case (30M) was infected by his father-in-law (57M).
The circumstantial epidemiological data can be strongly supported or refuted by sequence data. The sequence for the Hong Kong index case, A/Hong Kong/5942/2013, has been published. It has a novel constellation which includes five gene segments (PB2, PB1, PA, NP, NS) which are most closely related to H9N2 sequences circulation in Hong Kong, which includes three gene segments (PB1, PA, NP), which are easily distinguished from the August H7N9 sequence, A/Guangdong/1/2013. Thus, a match between sequences from the first two confirmed cases (treated at TMH) would strongly support nosocomial (human to human) transmission. Similarly, a match between the sequences from the two family members in Hangzhou (57M and 30M), which are more likely to match the October sequences from Zhejiang (A/Zhejiang/22/2013 and A/Zhejiang/DTID-ZJU10/2013), would also support H2H transmission between the family members.
Release of sequences from the three recently confirmed cases in Hong Kong (80M) and Zhejiang (57M and 30M), would be useful.