# 7544
A press release today from the British Medical Journal highlights research, scheduled to be published today, that finds at least one instance of `probable person-to-person transmission’ of the H7N9 virus last spring in China.
As we’ve discussed before, when it comes to proving human-to-human (H-2-H) transmission of an emerging virus, the bar is set pretty high. When there are other, equally plausible explanations (e.g. shared environmental exposures), then H-2-H cannot be assumed.
In this case, researchers not only have a timetable that is suggestive of H-2-H transmission within a family, the two patients (60 y.o. father & 32 y.o. daughter) were found to be infected with almost genetically identical virus strains.
The study has not yet gone live on the BMJ website, so I’ll update this post with a link when one becomes available.
UPDATE: The paper is now available (along with a 5 minute video abstract) at the following link.
Probable person to person transmission of novel avian influenza A (H7N9) virus in Eastern China, 2013: epidemiological investigation
BMJ 2013; 347 doi: http://dx.doi.org/10.1136/bmj.f4752 (Published 6 August 2013)
Cite this as: BMJ 2013;347:f4752
Below you’ll find the press release, after which I’ll return with a little more.
First probable person to person transmission of new bird flu virus in China
Tuesday, August 6, 2013 - 11:33
Research: Probable person to person transmission of novel avian influenza A (H7N9) virus in Eastern China, 2013: epidemiological investigation
Editorial: Human to human transmission of H7N9
The first report of probable person to person transmission of the new avian influenza A (H7N9) virus in Eastern China is published on bmj.com today.
The findings provide the strongest evidence yet of H7N9 transmission between humans, but the authors stress that its ability to transmit itself is “limited and non-sustainable.”
<SNIP>
The researchers acknowledge some study limitations, but say that the most likely explanation for this family cluster of two cases with H7N9 infection is that the virus “transmitted directly from the index patient to his daughter.” But they stress that “the virus has not gained the ability to transmit itself sustained from person to person efficiently.”
Although this is the first case where `probable’ H-2-H transmission has been documented, it isn’t the only H7N9 cluster where person-to-person transmission is suspected.
In early April Dr. Michael O’Leary, the World Health Organization’s representative in China, gave a media briefing where he described three `clusters’ of cases where human-to-human transmission may have occurred (see WHO: Transcript Of Media Briefing On H7N9).
There are 3 clusters officially reported, I mentioned one of them, the one with the father and 2 sons… 2 of whom, the father and the son who did not die, were confirmed H7N9.
So that’s one of the clusters, and we know about another cluster of a parent and a child, where the daughter was caring for the parent who was very sick, and became sick herself with the H7N9.
A third cluster as well, a husband-and-wife cluster. In both of those, people were sick with severe pneumonia, and so were linked clinically. But I think it’s still the case that in both of those, only one of them is so far confirmed, but the investigations are continuing. And then we know about the other are still under active investigation, the more recent situation here in Beijing, the 7-year-girl who is now released from the hospital, an asymptomatic, (meaning he had) no symptoms neighbor.
Laboratory investigation is still underway, but he is suspected as being positive as well. But that child was not ill.
For more details on the first cluster mentioned by Dr. O’Leary (an 87 year old man & his two sons) you may wish to revisit China Confirms H7N9 Shanghai Family Cluster.
Finding one or more clusters of H7N9 among close contacts isn’t terribly surprising. We’ve seen similar limited human-to-human transmission of the H5N1 virus in the past.
But as today’s study points out, numerous contacts of documented cases failed to contract the virus. So for now, at least, the virus appears incapable of transmitting in an efficient and sustained manner.
That good news is tempered somewhat by the studies we’ve seen over the summer (see Lancet: Tropism Of H7N9 In the Human Respiratory Tract , Science: H7N9 Transmissibility Study In Ferrets & Nature: H7N9 Pathogenesis and Transmissibility In Ferrets & Mice) that suggest the H7N9 virus may not need much in the way of adaptive changes in order to achieve efficient H-2-H transmission in mammals.
Which is why all eyes will be on China this fall to see if the H7N9 virus returns, and how it behaves in round two.
