background_and_summary_h7n9_v1

Background on H7N9 Virus

  • Subgroup of H7 viruses, circulating primarily among birds.

  • Other H7 viruses previously infecting humans: H7N2, H7N3, H7N7.

  • Cases mainly linked to poultry outbreaks, causing mild symptoms except for one death in the Netherlands.

  • H7N9 first reported in humans in March 2013 by China.

Epidemiology

  • Confirmed cases across 13 provinces in eastern China and Hong Kong.

  • Most infections linked to live animal markets; few family cluster cases with no sustained human-to-human transmission.

  • Case fatality rate at 22% as of January 28, 2014; majority of cases are male, median age 58 (66 for fatalities).

  • First wave of infections occurred February-May 2013; second wave began in October 2013.

Virology

  • H7N9 viruses show avian origin with signs of adaptation to mammals.

  • HA gene akin to A(H7N3) from ducks, NA gene similar to N9 in domestic ducks.

  • Adaptation involves increased binding to mammalian receptors and growth at mammalian body temperatures.

Human-Animal Interface

  • Infection source: infected poultry or contaminated markets.

  • Difficulty establishing clear links to poultry due to asymptomatic infections.

Clinical Presentation

  • Rapidly progressing severe pneumonia common; symptoms: fever, cough, shortness of breath.

  • Severe complications include ARDS, septic shock, and multi-organ failure.

  • Milder cases detected in healthy individuals through surveillance.

Treatment

  • H7N9 sensitive to neuraminidase inhibitors (e.g., oseltamivir, zanamivir), resistant to adamantanes.

  • Early oseltamivir administration effective in reducing severe cases and fatalities.

  • Resistance observed in some severe cases post-treatment; reassessment of antiviral strategies may be needed.

  • WHO treatment guidelines for A(H5N1) applicable.

Prevention

  • No effective vaccines available yet; WHO recommends vaccine development based on A/Anhui/1/2013-like virus.

  • Good hygiene practices advised to prevent infections.

  • Basic infection control measures include hand hygiene and use of PPE in healthcare settings.

  • Monitoring advised for contacts of confirmed cases; antiviral treatment recommended if symptoms develop.

Current WHO Actions

  • Ongoing monitoring and risk assessments since first case.

  • Coordination with national authorities for enhanced surveillance.

  • Support for H7N9 vaccine development and improved clinical management.

  • Collaborations with animal health organizations to assess public health risks.

WHO Recommendations

  • Rapid reporting of new H7N9 cases under IHR 2005.

  • Clinicians to consider H7N9 in patients with severe respiratory diseases.

  • Application of Standard Precautions for all patients in healthcare settings.

  • No special travel restrictions; screening at points of entry not advised.