Avian Influenza

Since December 2003, highly pathogenic H5N1 avian influenza viruses have swept through poultry populations across Asia and parts of Europe. The outbreaks are historically unprecedented in scale and geographical spread. Their economic impact on the agricultural sector of the affected countries has been large. From December 2003 to mid-July 2005, outbreaks of avian influenza A(H5N1) in poultry occurred in nine countries (Cambodia, China, Indonesia, Japan, the Republic of Korea, the Lao People's Democratic Republic, Malaysia, Thailand and Viet Nam). Since late July 2005, outbreaks in domestic poultry as well as wild birds have been reported in the Russian Federation, Kazakhstan, Romania, Mongolia, Turkey and Croatia. In addition, during this period outbreaks in poultry have increased again in Indonesia, Thailand, Viet Nam and China.Three contiguous WHO regions – Western Pacific, South-East Asia and Europe – now have H5N1 activity in wild fowl and poultry stocks. Evidence shows that the H5N1 virus is most likely endemic in many parts of Asia. It has established an ecological niche in poultry, making it extremely difficult to control outbreaks. Outbreaks have recurred despite aggressive control measures, including the culling of more than 140 million poultry as of September 2005.

Human cases, with an overall fatality rate around 50%, have been reported in Cambodia, Indonesia, Thailand and Viet Nam. Almost all human infections can be linked to contact with infected poultry, but isolated instances of inefficient human-to-human transmission may have occurred in Viet Nam in 2004, and possibly in Thailand and Indonesia. Influenza viruses are genetically unstable and their behaviour cannot be predicted. The risk of further human cases persists, as do opportunities for a human pandemic strain of the virus to emerge. For these reasons, the current outbreaks of influenza A(H5N1) in poultry and humans in Asia, has moved the world closer to a pandemic than any time since 1968, when the last such event occurred.

The WHO Western Pacific Regional Office emphasizes the following strategic approach to control the regional outbreak of avian influenza A(H5N1) and reduce the risk of an influenza pandemic.

AI Weekly Update Number 318 (3 February 2012)

1. Latest information on Human Avian Influenza cases

Since 2003 to 24 Jan 2012, the number of cases reported from 15 countries worldwide is 583 and 344 were fatal (CFR 59.0%). Among the countries with more than 10 reported cases, Cambodia had the highest CFR of 89.4% (17 out of 19).

Age distribution of the reported cases ranged from 3 months to 81 years old (median 19 years, n=560). The age group with the largest number of cases was 20-29 years of age (23.0%, 129/560), relative to other age groups (0-4; 5-9; 10-19; 30-39; 40-49; 50-59; 60-69; 70+ years). The highest CFR (73.3%) was among persons 10-19 years of age and lowest was among persons 0-4 years (25.7%) and persons 70+ years old (25.0%). 53.8% of the cases were female (300/558)

Table 1: Cumulative Number of Confirmed Human Cases (C) and Deaths (D) of Avian Influenza A (H5N1) Reported to WHO

2. Latest Human H5N1 cases in countries affected in 2012 (Updated 3 February 2012)

Cambodia. The latest reported case in 2012 was 2 year old male from Banteay Meanchey Province. He developed symptoms on 3 Jan, admitted to hospital on 9 Jan, and died on 18 Jan. The boy was exposed to sick poultry in his village. The National and Local Rapid response teams are conducting outbreak investigation and response

China. The latest reported case is 39 year old male, from Guiyan city, Guizhou province. He developed symptoms on 6 Jan, admitted to hospital, died on 22 Jan. The case was laboratory diagnosed by Guizhou CDC and confirmed by China CDC on 22 Jan. Investigation into the source of infection is ongoing. Close contacts of the cases are being monitored and to date all remain well.

Egypt. Two cases are reported on 19 Jan 2012. The first case is 2 year old female from Cairo Governorate. She was an outpatient with ILI symptoms at Helwan Fever Hospital on 30 Oct 2011. This case was confirmed by the Central Public Health Laboratory through periodic testing of samples collected from sentinel ILI surveillance sites. She had a history of exposure to backyard poultry. The second case is a 31 year-old male from Fayium governorate. He developed symptoms on 1 Jan 2012, and is still hospitalized under the critical care unit. He had exposure to backyard poultry.

Indonesia. The latest reported case in 2012 is a 5 year-old female. She was identified by a surveillance team during an investigation in the area on 7 Jan and referred to a hospital. 13 Jan, she had breathing difficulties. Her condition deteriorated and she died on 16 Jan. Epidemiological investigation indicated that she was a family contact of the case who died on 7 Jan (23 y-o male) and frequently had direct contact with the same pigeons as that case and the same household environmental.

Viet Nam . The case was an 18 year-old male from Kien Giang Province. He developed symptoms on 10 January 2012 and was admitted to hospital on 14 January 2012 but died on 16 January 2012. Confirmatory test results for influenza A (H5N1) were obtained on 17 January 2012 by Pasteur Institute, the WHO National Influenza Centre in Ho Chi Minh City, Viet Nam. The man was reportedly exposed to ducks. Pasteur Institute in Ho Chi Minh City and the local health sector are conducting outbreak investigation and response.

3. Latest information on avian influenza outbreaks in poultry (as of 3 February 2012)

Source: OIE WAHID Weekly Disease Information Reports- FAO ECTAD HPAI SITUATION UPDATE (EMPRES/GLEWS); official report ONLY- Update on Avian Influenza in Animals (Type H5)- Official Report from the Ministry of Agriculture/Livestock

Situation Updates

Fact sheets

News and press releases

24 March 2010
Avian influenza still a threat, says WHO
[full text]

24 November 2009
Avian influenza remains a global threat, says WHO
[full text]

25 September 2008
WHO urges countries to speed up their ability to fight new diseases
[full text]

[more news]

Relevant publications and documents

WHO Global Influenza Preparedness Plan
The WHO global influenza preparedness plan has been prepared to assist WHO Member States and those responsible for public health, medical and emergency preparedness to respond to threats and occurrences of pandemic influenza

WHO Influenza Pandemic Preparedness Checklist
November 2004 version

Influenza pandemic preparedness and response

Stop the Spread - Measures to Stop the Spread of Highly Pathogenic Bird Flu at its Source
This document outlines strategies to minimise the disease in the production, distribution, processing and marketing of poultry, thereby reducing the risk to human health from Avian Influenza.The strategies where developed during the FAO/OIE/WHO Consultation on Avian Influenza and Human Health: Risk Reduction Measures in Producing, Marketing, and Living with Animals in Asia, held in Kuala Lumpur, Malaysia, from 4 to 6 July 2005 (full meeting report is below).