Thursday, 9 January 2014

H5N1: 1st fatal case in North America...[UPDATED x4-FINAL]

An otherwise healthy resident of Alberta, Canada, died 3-Jan after contracting influenza A(H5N1) virus during a visit to Beijing ,China. The person did not leave the Beijing area and did not visit live bird market. The victim returned on Air Canada flights (according to a Tweet from @HelenBranswell), showing signs and symptoms on admission to hospital 1-Jan which included high fever and lethargy without cough or other signs of acute respiratory tract illness. The patent died of meningoencephalitis. The lab confirmed H5N1 7-Jan. 

Canadian officials will not be describing the patients age, sex or occupation. Giving the region would be enough to identify the patient given there is only 1 case.

A highly pathogenic avian influenzavirus (HPAI or "high-path) that can kill the birds it infects, H5N1 has been confirmed in 648 people across 15 countries since its identification in a 3-year old boy in Hong Kong in May 1997 (first identified in a goose in 1996). There were 38 cases identified globally in 2013, with 24 deaths. A slow-burn that seems comparable to H7N9's current spread. How often H5N1 is considered in the screening of influenza-like illness I do not know; another similarity might be under-reporting/limited prospective PCR-based screening.

As ever, these sporadic imported cases also serve to highlight that the pathogen is circulating at the source. The route of acquisition for this case is unclear at this stage. H5N1 does not readily transmit among humans requiring close contact with birds and there has been no sustained human-to-human transmission.

When a human does become infected by the virus, severe acute respiratory distress syndrome can result. This is ascribed to the availability of receptors in the deeper airways and lungs, which bind the virus and trigger the person's own immune-mediated disease via a "cytokine storm"; a large scale release of the chemicals our bodies usually employ to keep virus infections in check, but on a larger scale with more severe consequences to the host. Such a storm does not commonly occur following infection by a seasonal influenza virus (e.g. H3N2) infection, 

The WHO does not list any H5N1 cases in the area around Beijing on its 2013 map (18-Dec-2013). An out-of-date timeline of "major" H5N1 events lists human cases in Beijing in Nov-2003 and Dec-2008. Major outbreaks among birds in China have centered around Qinghai lake.

There is no H5N1 component in the current seasonal influenza vaccine, but then there is no significant risk to the Canadian public health from H5N1.

The current WHO phase of pandemic alert for H5N1 is ALERT:
This is the phase when influenza caused by a new subtype has been identified in humans. Increased vigilance and careful risk assessment, at local, national and global levels, are characteristic of this phase. If the risk assessments indicate that the new virus is not developing into a pandemic strain, a de-escalation of activities towards those in the interpandemic phase may occur.

As the Public Heath Agency Canada recommend, Think-Tell-Test....
  • implement best practices for triage, infection control and patient management as indicated
  • Consult your local Public Health for assistance in SRI/severe ILI patients with the following:
    • Recent travel or contact with travelers to an affected area with confirmed H5N1 activity in humans and/or domestic poultry
  • Consult your local Public Health for guidance on appropriate testing, recommended procedures and prioritization for H5N1 investigation IF significant exposure history has been established which may include:
    • Close contact (within 1 metre, i.e. touching distance) with a confirmed human case of H5N1 or
    • Close contact with sick or dead domestic poultry or wild birds

Other news and related information sources include...