Sunday, January 22, 2017

HK CHP Statement On Increasing H7N9 And Seasonal Flu Activity

Credit HK CHP


As I mentioned yesterday, with the fragmented flow of information from the Chinese Mainland on their H7N9 epidemic, Hong Kong's (and to a lesser extent, Macao's) response to the threat is probably our best, and earliest indicator of how serious the situation has become.

While the level of concern expressed by HK's CHP is certainly elevated, reassuringly we haven't seen any indication they are taking extraordinary measures.  

Instead, we see continual (almost daily) warnings to the public to avoid contact with poultry or visits to live bird markets or farms, to maintain good `flu hygiene', and for high risk groups to get this year's flu vaccine.

The government has also ramped up monitoring (including thermal scanning) of incoming visitors at all boundary control points, but this is their standard response every year.  First today's statement, then I'll be back with a bit more on some of their interventions.     

  The Centre for Health Protection (CHP) of the Department of Health today (January 22) drew the public's attention to increasing activity of avian and seasonal influenza around the Lunar New Year.

     "We would like to remind travellers during the Lunar New Year holidays to avoid poultry contact and not to visit poultry markets to guard against avian influenza. Those visiting the Middle East should avoid camel contact and should not visit farms or barns to prevent Middle East Respiratory Syndrome. Locally, for better personal protection before the winter influenza season, the public, in particular young children and elderly persons, are urged to receive seasonal influenza vaccination early," a spokesman for the CHP said.

     "During the festive season, wash hands frequently and eat thoroughly cooked and healthy food. Strict personal, hand, food and environmental hygiene remain keys to safeguarding infectious diseases," the spokesman said.

A. Avian influenza A(H7N9)

     The activity of avian influenza A(H7N9) has been increasing markedly since the end of 2016. The Mainland health authorities reported six and 106 human H7N9 cases in November and December 2016 respectively. In the first half of January 2017, 111 cases were detected. The situation this winter has been progressing much faster than the situation last winter.

     In the neighbouring Guangdong, 11 human H7N9 cases, with two deaths, were recorded in the first half of this month. The H7-positive percentage of environmental samples from live poultry markets was substantial at 9.42 per cent in the first week of this month. In Hong Kong and Macau, four cases (imported) and two cases were recorded respectively.

     "As there is a likely risk that environments with live poultry in the Mainland are contaminated with avian influenza viruses, the public, especially poultry traders and travellers, should be on full alert," the spokesman said.

     "Travellers to the Mainland or other affected areas must avoid visiting wet markets, poultry markets or farms. Stay alert to possible backyard poultry when visiting relatives and friends. Avoid buying live or freshly slaughtered poultry and avoid touching poultry/birds or their droppings," the spokesman added.

     More information and the risk assessment have been reported in the CHP's latest bi-weekly Communicable Diseases Watch.

B. Seasonal influenza

     Among respiratory specimens received by the CHP's Public Health Laboratory Services Branch, the positive percentage of seasonal influenza viruses increased from 4.38 per cent in the week ending December 24, 2016, to 8.13 per cent in that ending January 14, 2017. Most detections were influenza A(H3N2).

     Seven institutional outbreaks of influenza-like illness affecting 26 persons were recorded in the week ending January 14, 2017, compared to two outbreaks involving seven persons in the preceding week. As of January 19, six outbreaks affecting 25 persons were recorded last week.

     "The surveillance data in the past few weeks show that the local influenza activity is increasing and the winter influenza season is expected to arrive very soon," the spokesman said.

     "We urge the public, particularly children, the elderly and those with underlying illnesses, to get vaccinated as early as possible to prevent seasonal influenza as it takes about two weeks for antibodies to develop in the body after vaccination," the spokesman added.

     As of January 15, about 360 000 and 258 000 doses of seasonal influenza vaccines had been administered via the Government Vaccination Programme (free vaccination) and the Vaccination Subsidy Scheme (subsidised vaccination) respectively, increasing 8.6 and 53.6 per cent from the same period in the last season.

     The latest surveillance data have been reported in the CHP's weekly Flu Express.

Ends/Sunday, January 22, 2017

Issued at HKT 14:00

While the seasonal flu shot is almost certainly ineffective against H7N9 (or for that matter H5N6), the CHP continues to promote it for two very good reasons.  First, seasonal flu is a killer in its own right,  and there's little doubt it will be impacting Hong Kong residents over the next couple of months.

But secondly, the higher the vaccination rate, the lower the likelihood that someone in Hong Kong will be coinfected with both seasonal and avian flu.   A rare, but not unheard of condition that can give rise to a reassorted flu virus.  One with genetic components from both parental subtypes.

This is not an idle concern (see CIDRAP: Analysis of new H7N9 wave warns of coinfection threat), and one we looked at in depth again last summer in JVI: Reassortant Seasonal-Pandemic H1N1 viruses In Co-infected Humans.  

For more background, there is an excellent 3 minute video by NIAID on Youtube called  How Influenza Pandemics Occur.

Granted, based on exposure risks, vaccination levels, and shear numbers involved - if a reassortment were to occur - it most likely happen on the mainland. Still, there is value in preventing it from happening in your own backyard, as that would allow little lead time to prepare.

The setting up of health checkpoints and thermal scanners at entry control points - while no doubt reassuring to the residents of Hong Kong - is unlikely to prevent entry of most infected individuals from the Mainland.   Some of the reasons for this include:
  • Some may still be silently incubating the virus, and will become symptomatic hours or days after arrival
  • Others may have other symptoms, but no fever
  • Some may be taking antipyretics (fever reducers) to ease symptoms or evade detection
  • And some may simply be asymptomatic carriers of the virus. 
We know this because previous attempts to interdict SARS and H1N1 using airport screeners and/or thermal scanners have been well studied. In 2010, in  Japan: Quarantine At Ports Ineffective Against Pandemic Flu, I wrote about a study that found between asymptomatic or mild infections, and a silent incubation period of several days, there wasn’t much chance of long-term success.
For every person identified, and quarantined, by port authorities  - researchers estimate 14 others infected by the virus entered undetected.

Entry screening isn’t useless, as it can identify acutely ill individuals when they are likely to be the most contagious so they can be promptly isolated, and it can provide important surveillance information. And it might even help slow the rate of entry of an emerging disease into a region, allowing additional time to mount public health interventions.

But as far as preventing it from entering, well the odds are pretty long.

The advice to maintain good flu hygiene (cover coughs & sneezes, bin tissues, use hand sanitizers), to avoid contact with live birds or markets, and to wash hands frequently may sound lame - but it is genuinely good advice during any flu season - and even more so during this heightened period of H7N9 activity.  
Lastly, we've seen this drill before, with both Chinese New Year's and the Hajj, and so far - despite elevated concerns - we've not seen either spark a major increase in avian flu or MERS. 

A pandemic emerging from either of these mass gathering/migration events is a low probability - high impact event.  One that we must take seriously, but one that might not happen for years.

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