Thursday, November 19, 2015

Study: Probable Nosocomial Transmission Of H7N9 In China






Although the story has appeared in a number of news outlets overnight, the actual BMJ article (and corresponding editorial) upon which they are based have not gone live yet. Until that happens, we’ll have to content ourselves with one of the preliminary reports. 

The gist of the story is that last February a man with recent poultry exposure was hospitalized in a general ward in a Zhejiang hospital for 5 days before being identified as having H7N9, and during that time another patient in the same ward contracted the virus. 


Both men died, and genetic testing showed their viruses to be almost identical. First a link and some excerpts from the  MedicalXpress, then I’ll be back with more.


Evidence of probable transmission of bird flu virus between two unrelated individuals

November 18, 2015

Previous reports of person to person transmissions have all occurred in family clusters, suggesting that either common exposures or genetic susceptibility might contribute to the infection.

The study describes two patients who shared the same ward in a district hospital in Zhejiang Province, China in February 2015.

The first (index) case was a 49 year old man who became ill after buying two chickens from a live poultry market for the wedding ceremony of his elder daughter. He developed a fever, cough, and sore throat and was admitted to a district hospital on 18 February.

He was diagnosed with H7N9 virus on 24 February and was admitted to a specialist hospital ward with intensive care facilities. He died of multi-organ failure on 20 April.

The second case, a 57 year old man with a history of chronic lung disease (COPD), developed flu-like symptoms after staying on the same ward of the district hospital as the index case for five days (18 to 23 February).

He was diagnosed with H7N9 virus on 25 February and died of respiratory failure on 2 March.

A total of 38 close contacts of both cases, including family members and health workers, were tested for the virus.

Two samples taken from the chickens purchased by the index patient as well as five of 11 samples from the live poultry market he visited were positive for H7N9 virus.

The second patient had no history of poultry exposure for 15 days prior to his illness. Samples from his home, from chickens raised by his neighbours, and a local chicken farm were all negative for H7N9 virus.

Yet the genetic sequence of H7N9 virus from the second patient was nearly identical to that from the index patient, and genetically similar to the virus samples taken from the live poultry market visited by the index patient.

The researchers stress that they cannot completely rule out an unidentified environmental exposure that might explain the H7N9 infection in the second patient.

However, because no other common exposure was identified, they say "it seems most likely that the H7N9 virus was transmitted from the index case to the second case during their stay on the same ward."

Their findings also strongly suggest that the live poultry market is the most probable source of influenza H7N9 virus infection for the index case.


More information: Nosocomial transmission of avian influenza A (H7N9) virus in China: epidemiological investigation,

Editorial: Nosocomial transmission of avian influenza virus A (H7N9),

Provided by: British Medical Journal search and more info website


We’ve had pretty good evidence of household transmission of the H7N9 virus for several years (see 2014 WHO H7N9 FAQ   &  EID Journal: H7N9 In Two Travelers Returning From China - Canada, 2015), and given the fact that only the `sickest of the sick’ are ever tested for the virus, there’s a pretty good chance that a substantial number of mild cases go unnoticed.


One study conducted after the first wave in the spring of 2013 – where just 134 cases were recorded – estimated the number of cases really ran into the thousands (see Lancet: Clinical Severity Of Human H7N9 Infection).  Their estimate?  Anywhere between 1500 and 27,000 symptomatic infections.

Although no sustained transmission has been observed in the community (an observation reinforced by very few secondary infections in contacts of known cases), the H7N9 virus continues to evolve and change over time (see EID Journal: H7N9’s Evolution During China’s Third Wave – Guangdong Province).

The H7N9 virus has, at last count (see Nature report), produced at least 48 genotypes, spread across three major clades, and it is likely that this constellation of H7N9 variants will continue to expand.


While it may be entirely coincidental, the day-to-day reporting of H7N9 out of China went from relatively sparse to nearly nonexistent in early March of this year – a week after this second patient died -  something I blogged about in H7N9: No News Is . . . . Curious on March 19th.  

Since then we’ve seen nothing but barebones reporting of cases, often just totals in EOM epidemiological reports, with little or no useful detail.  


A far cry from the sort of openness the Chinese displayed during the first two waves of the virus.