Credit CHP
# 6987
Hong Kong’s CHP publishes an excellent Communicable Diseases Watch report every two weeks, and along with a summary of selected notifiable diseases and outbreaks, usually provides an in-depth look at one or two diseases.
Today’s CDW report (Vol 10 Issue 5) includes a update on the progression of H5N1 around the globe.
Below, some excerpts from this detailed report, but follow the link to read it in its entirety.
Update on H5N1 avian influenza
Reported by Miss Amy Li, Scientific Officer, Respiratory Disease Office, Surveillance and Epidemiology Branch, CHP.
Avian influenza infection in human is caused by influenza viruses, such as influenza A(H5N1), that mainly affect birds and poultry. Severe infection can result in severe respiratory failure, multi-organ failure and even death. Human infection with H5N1 is a rare event. Most cases recorded to date were sporadic infections, with limited human-to-human transmission in some cases. Below we summarize the latest global and local situation of human H5N1 avian influenza infection.
Global SituationAs of March 1, 2013, 622 human cases of H5N1 infection (including 371 deaths) have been reported to the World Health Organization (WHO) from 15 countries since 2003. Indonesia has the highest cumulative number of human H5N1 cases, followed by Egypt and Vietnam. From 2005 to 2007, about 100 confirmed human cases of H5N1 avian influenza were reported to WHO annually. In the years 2008-2012, the number of cases recorded fluctuated from 32 to 73. Among cases since the beginning of 2012, about 90% had documented exposure to sick or dead poultry or poultry environments such as live poultry markets.
Twelve human cases were recorded so far this year (as of March 1, 2013), include 9 cases from Cambodia, 2 cases from Mainland China (Guizhou) and 1 case from Egypt. Eleven of them were fatal. According to WHO, epidemiological investigations revealed that all cases from Cambodia this year had either exposure to poultry or recent deaths among poultry in their villages. While the case from Egypt also had exposure to backyard sick and dead poultry i, the 2 fatal cases from Mainland China (Guizhou) had no clear history of contacting poultry before symptom onset.
According to WHO (as of March 1, 2013), age distribution of all cases ranged from 3 months to 81 years (median 18 years, n = 599).The age group with the largest number of cases was 20-29 years of age (22.4%, 134/599), relative to other age groups (0-4; 5-9; 10-19; 30-39; 40-49; 50-59; 60-69; 70+ years). 53.9% of the cases were female (322/597). A total of 371 cases died,giving a case fatality rate of 59.6%.The highest case fatality rate (CFR) (73.2%) was among persons 10-19 years of age. Among the countries with more than 10 reported cases, Cambodia had the highest CFR of 90.0% (27 out of 30) i. Figure 1 shows the annual trend of human cases.
Outbreaks in poultry and wild birds continue to occur sporadically across the globe. H5N1 outbreaks in poultry were recorded in Bangladesh, Bhutan, Cambodia, China (Guangdong), India, Nepal and Vietnam in the past 6 months (September 1, 2012, to March 1, 2013) (World Organization for Animal Health). Indonesia and Egypt have also declared avian influenza endemic in poultry since September 2006 and July 2008, respectively.
According to the latest risk assessment issued by WHO on February 15, 2013, any time influenza viruses are circulating in poultry, sporadic infections or small clusters of human cases are possible especially in people exposed to infected poultry kept in households. However, currently, this H5N1 virus does not appear to transmit easily among people and therefore the risk of community level spread of the virus remains low.
