BMJ: `Probable Person-to-Person Transmission’ Of H7N9

 

 

# 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.”

(Continue . . . )

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.

Eurosurveillance: H2H Transmission of NCoV In UK Family Cluster

Photo Credit NIAID

 

# 7007

 

Although we’ve known since the middle of last month (see HPA: UK NCoV Cluster Expands To Three Cases) that human-to-human transmission was strongly suspected in the recent UK family cluster of novel coronavirus cases, today we get considerably more detail via a Rapid Communications that appears in the journal Eurosurveillance.

 

Eurosurveillance, Volume 18, Issue 11, 14 March 2013

Rapid communications

Evidence of person-to-person transmission within a family cluster of novel coronavirus infections, United Kingdom, February 2013

The Health Protection Agency (HPA) UK Novel Coronavirus Investigation team

 

In February 2013, novel coronavirus (nCoV) infection was diagnosed in an adult male in the United Kingdom with severe respiratory illness, who had travelled to Pakistan and Saudi Arabia 10 days before symptom onset.

 

Contact tracing identified two secondary cases among family members without recent travel: one developed severe respiratory illness and died, the other an influenza-like illness. No other severe cases were identified or nCoV detected in respiratory samples among 135 contacts followed for 10 days.

What follows is long and fairly detailed account of the epidemiological investigation into these family members, and their contacts. 

 

Interestingly, this investigation found that the index case, recently returned from Pakistan and Saudi Arabia, was co-infected with influenza A and that both family members who became infected were co-infected with Type 2 parainfluenza virus.

This raises the intriguing possibility that a respiratory virus co-infection might somehow influence the severity, and/or transmissibility of the NCoV virus.

 

At the same time, it serves to remind us that a positive influenza rapid test doesn’t necessarily rule out the possibility of a concurrent NCoV infection.

 

In the index case described in this report, a presumptive diagnosis of Influenza A was made on February 1st, and the NCoV diagnosis was not made until a full week later.

 

 

The third member of this family cluster only developed mild symptoms, and did not require hospitalization.  This being the first clear indication that mild cases may be present, giving rise to the following commentary from this paper:

 

. . .  This first reported case of a milder nCoV illness raises the possibility that the spectrum of clinical disease maybe wider than initially envisaged, and that a significant proportion of cases now or in the future might be milder or even asymptomatic.

 

This highlights the importance of intensive contact tracing and virological and serological follow-up around all confirmed cases of nCoV. The application of recently developed serological assays in one case¬–contact study did not provide evidence of asymptomatic infection, although the contacts investigated were exposed late in the case’s illness, when the viral load might be lower [11].

 

Paired sera are being gathered from contacts in this current investigation to determine whether there may have been more widespread mild or asymptomatic infection.

 

We also learn that – based on a very limited dataset – NCoV appears to have a:

 

`putative incubation period ranging from one to nine days and a serial interval (time between onset of illness in index case and secondary case) of 13 to 14 days.’

This is a fascinating report, well worth reading in its entirety.  I’ve only excerpted a few of the highlights.

 

The authors write towards the end:

 

Public health implications

 

These findings suggest that although person-to-person infection is possible, there is no evidence at present of sustained person-to-person transmission of nCoV in the UK in relation to this cluster. The limited transmissibility is consistent with the data available to date, with only two other reports of small, self-limited clusters of severe disease in the Middle East: one in a healthcare setting and the other in a household setting [5].

 

Furthermore, intensive follow-up of close contacts of two other cases imported to European countries has failed to demonstrate onward transmission [10,11].

<SNIP>

All confirmed nCoV cases detected to date, apart from the two secondary cases in the UK cluster, spent time in the Middle East during the putative incubation period. This, together with our observations of limited secondary transmission, highlights the importance of ongoing vigilance and rapid investigation of cases of severe respiratory illness in residents of and travellers from that area.

 

Further work is required to determine how widely nCoV is circulating globally. In particular serological investigations are needed on the extent of recent infection in various populations, as well as virological investigation of cases of severe undiagnosed respiratory illness in settings both in and beyond the Middle East.

 

While researchers are obviously learning more about NCoV with each passing day (see Nature: Receptor For NCoV Found), it may be some time before they can tell us just how much, or how little, a public health threat this emerging virus actually poses.

 

For now, enhanced surveillance and vigilance in contract tracing is key. 

 

Stay tuned.