Tuesday, February 24, 2015

Hong Kong: Update On 3rd Imported H7N9 Case



# 9746


We’ve an update from Hong Kong’s CHP this morning on their epidemiological investigation into this seasons’ 3rd imported H7N9 case. This is the 13th known importation into Hong Kong since H7N9 emerged two years ago, and authorities have contact tracing and surveillance pretty much down to a science. 


While human-to-human transmission of the H7N9 virus has only rarely been reported, the incubation period is thought to be up to 10 days, and so arrangement are being made for asymptomatic contacts to be quarantined at the Lady MacLehose Holiday Village in Sai Kung.

Lady MacLehose Holiday Village

We’ve seen similar arrangements in the past both in Hong Kong and in Singapore (see Singapore MOH Puts Quarantine Chalets On Standby).  Symptomatic contacts are quartered in hospital isolation rooms.

Here is today’s update, after which I’ll return with a bit more:


Update on imported human case of avian influenza A(H7N9)

The Centre for Health Protection (CHP) of the Department of Health (DH) today (February 24) reported the latest updates on the third imported human case of avian influenza A(H7N9) in Hong Kong this winter, and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

Epidemiological investigations by the CHP have so far located 17 close contacts and 99 other contacts of the patient.

(A) Close contacts
The close contacts will be put under quarantine and prescribed with antiviral presumptive treatment until the completion of the five-day treatment, or 10 days since last exposure to the patient, whichever is earlier. They include:

  • An asymptomatic family member of the patient who tested negative for influenza A virus;
  • Five asymptomatic healthcare workers (HCWs) involved in Queen Mary Hospital (QMH);
  • Seven in-patients admitted to the same cubicle as the confirmed patient in QMH among which six were asymptomatic while the remaining one is under tracing; and
  • Three patients and one who accompanied one of them attending the same private clinic in Aberdeen with the confirmed patient. They are all asymptomatic.

The Lady MacLehose Holiday Village in Sai Kung under the Leisure and Cultural Services Department has been converted to a quarantine centre for asymptomatic close contacts, including the HCWs involved in QMH.

(B) Other contacts
Other contacts have been put under medical surveillance and they include:

  • Another asymptomatic family member who visited the confirmed patient in QMH;
  • 77 HCWs involved in QMH;
  • 15 asymptomatic clinic contacts including a private doctor, staff and patients of the private clinic; and
  • Six colleagues of the patient among whom one had mild upper respiratory tract infection symptoms before exposure to the patient while the rest are asymptomatic.

Investigations and contact tracing are ongoing.

Ends/Tuesday, February 24, 2015
Issued at HKT 17:18


As mentioned yesterday, with this year’s severe, and concurrent, seasonal flu outbreak in Hong Kong there are enhanced concerns that someone could be simultaneously infected by both the H7N9 virus and H3N2.  Although the outcome of such a rare event is unpredictable, it could theoretically lead to the creation of a `hybrid’ or reassortant virus.


Yesterday the HK CHP released the following statement regarding the genetic profile of H7N9 viruses detected this year (excluding the latest one, on which genetic characterization is under way).


"While the activity of avian influenza viruses in the Mainland and human seasonal influenza viruses in Hong Kong remains high this winter and heightened vigilance and extra attention to hygiene are warranted, we will closely monitor the virus activity and genetic nature. Genetic analysis to date has revealed that H7N9 viruses confirmed in Hong Kong have remained to be of avian origin and had no significant differences from those detected in the Mainland, nor has there been evidence of reassortment with genes from human seasonal influenza viruses or resistance to the antiviral oseltamivir (Tamiflu)."


Previously, in the Lancet: Coinfection With H7N9 & H3N2, we saw the first evidence of co-infection with the newly emerged H7N9 virus and a seasonal flu virus in a human. While last October, in EID Journal: Human Co-Infection with Avian and Seasonal Influenza Viruses, China, we looked at co-infections in 2 patients in Hangzhou, in January 2014.


In all of three of these cases, no reassortant virus was detected.  Yet we know from experience that these sorts of events are possible (see pH1N1 – H3N2 A Novel Influenza Reassortment).


While rarely detected, influenza A coinfections are probably more common than we realize.  Luckily, most do not result in the creation of a reassorted virus - and of those that do - most end up being evolutionary failures.


The odds of any one viral tryst producing a viable, humanized virus is probably fairly remote.


The concern is, if these viruses get enough rolls of the genetic dice, they will eventually roll a natural.  Which is why we watch Hong Kong, mainland China, and Egypt so carefully this time of year.

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