Changes

The most recent cases reported in China on the 29th March 2013 involve the A/H7N9 subtype (hereafter referred to as H7N9), which has been shown to be more virulent in people than poultry. China confirmed three initial human cases, all of whom died. Currently (as of 29th April 2013) there are 126 confirmed cases of H7N9 in humans in China7.

The most recent cases reported in China on the 29th March 2013 involve the A/H7N9 subtype (hereafter referred to as H7N9), which has been shown to be more virulent in people than poultry. China confirmed three initial human cases, all of whom died. Currently (as of 29th April 2013) there are 126 confirmed cases of H7N9 in humans in China7.

The human and animal sequences have been shown to be closely related but diverse enough to conclude that the virus has been circulating for a while (probably amongst animals). The H7N9 strain identified in people has been found to have amino acid substitutions not found in poultry that are associated with further adaptation to humans8. This adaptation to mammals is of concern and suggests that further adaptation may occur22. Currently no animal outbreaks have been identified in the area surrounding the confirmed cases and only a small proportion of birds have tested positive for the virus. However 77% of those people infected with H7N9 have been exposed to poultry/swine (including live bird markets). Three family clusters of 2-3 cases each have been identified where limited human to human transmission may have occurred22. Of 71 cases reported with complete data, 54 had an underlying health condition and the median age was 61 years, compared to median age of 26 years for H5N17.

The human and animal sequences have been shown to be closely related but diverse enough to conclude that the virus has been circulating for a while (probably amongst animals). The H7N9 strain identified in people has been found to have amino acid substitutions not found in poultry that are associated with further adaptation to humans8. This adaptation to mammals is of concern and suggests that further adaptation may occur22. Currently no animal outbreaks have been identified in the area surrounding the confirmed cases and only a small proportion of birds have tested positive for the virus. However 77% of those people infected with H7N9 have been exposed to poultry/swine (including live bird markets). Three family clusters of 2-3 cases each have been identified where limited human to human transmission may have occurred22. Of 71 cases reported with complete data, 54 had an underlying health condition and the median age was 61 years, compared to median age of 26 years for H5N17.

At the moment it is thought that H7N9 was transmitted from healthy poultry or swine to people either directly or through contaminated environments9. As few H7N9 positive birds have been detected, this may indicate that the virus is widespread in poultry and is asymptomatic which could lead to silent spread of the virus.

At the moment it is thought that H7N9 was transmitted from healthy poultry or swine to people either directly or through contaminated environments9. As few H7N9 positive birds have been detected, this may indicate that the virus is widespread in poultry and is asymptomatic which could lead to silent spread of the virus.