Influenza

H5N1 avian influenza: a chronology of key events

12 February 2004

12 December 2003
– The sudden death of chickens at a farm in Eumsung district, near the capital city of Seoul, prompts suspicions of an epidemic of highly pathogenic avian influenza in the Republic of Korea. Tests are initiated. Of the 24,000 chickens on the farm, 19,000 died between 5 and 11 December. The remaining 5,000 were culled.

17 December
– Authorities in the Republic of Korea formally report an epidemic of highly pathogenic avian influenza, caused by the H5N1 strain of the virus, at the chicken farm. This is the first time that highly pathogenic avian influenza has ever been reported in the country. No symptoms are reported in farmers in close contact with the infected chickens.

26 December
– Authorities in the Republic of Korea report the spread of H5N1 infection to chicken and duck farms in 5 provinces. Altogether, more than 1.3 million chickens and ducks have died or been destroyed.

5 January
– Health authorities in Viet Nam inform the WHO office in Hanoi of an outbreak of severe respiratory illness in 11 previously healthy children hospitalized in Hanoi, with the most recent hospital admission on 4 January. Seven cases were fatal and two patients remain critically ill. A 12th case, a sibling of one of the Hanoi cases, died of a respiratory illness in a provincial hospital.
– Included in this report are six children, aged 9 months to 12 years, who died in a Hanoi hospital of respiratory illness of unidentified cause between 31 October and 30 December 2003. For the first 5 cases, no samples are available for analysis. Samples are available for the 6th case, a 12-year-old girl who was admitted to hospital on 27 December and died three days later. All of these cases were identified retrospectively based on hospital records.
– It is not known whether all cases were caused by the same pathogen. The pathogen is unknown, but thought to be an influenza virus or an adenovirus. Arrangements are made for testing.
– WHO assistance in responding to the outbreak is requested. WHO headquarters and the regional office in Manila are alerted.

6 January
– A member of the press informs the WHO office in Hanoi of rumoured chicken deaths in southern Viet Nam. The regional office in Manila is alerted.

7 January
– WHO informs public health officials worldwide through its electronically distributed Outbreak Verification List.

8 January
– Authorities in Viet Nam report outbreaks of highly pathogenic avian influenza, caused by the H5 subtype (later confirmed as the H5N1 strain), at farms in the southern provinces of Long An (2 farms) and Tien Giang (1 farm). Around 70,000 birds died or were destroyed. This is the first time that highly pathogenic avian influenza has ever been reported in the country.

11 January
– Since the 5 January report, Vietnamese officials have identified two further cases of severe respiratory illness (another child and the first adult), bringing the total since end-October in Hanoi’s hospitals to 13.
– Tests on samples from two fatal cases in Viet Nam (the 12-year-old girl and a 10-year-old boy), performed by Hong Kong’s National Influenza Centre, confirm infection with the H5N1 avian influenza virus strain.
– WHO alerts its partners in the Global Outbreak Alert and Response Network (GOARN).

12 January
– Hong Kong’s National Influenza Centre confirms infection with H5N1 in a third fatal case in Viet Nam, the 30-year-old mother of the 12-year-old girl.
– Vietnamese health authorities and WHO announce laboratory confirmation of the three cases of human infection with avian H5N1.
– Confirmation of these three cases marks the third time in recent years that the H5N1 strain has jumped from its avian host to infect humans. The previous human infections occurred in Hong Kong in 1997 (18 cases, 6 of which were fatal) and again in Hong Kong in February 2003 (2 cases, one of which was fatal). The 1997 outbreak coincided with highly pathogenic H5N1 avian influenza in Hong Kong’s poultry farms and live markets. The two cases in 2003 had returned to Hong Kong following travel in southern China.
– Authorities in Japan report an outbreak of highly pathogenic avian influenza, caused by the H5N1 strain, at a farm in Yamaguchi prefecture. This is the first report of highly pathogenic avian influenza in the country since 1925.

13 January
– Authorities in the Republic of Korea announce the spread of H5N1 infection to an additional farm, dashing hopes that the epidemic had been brought under control. To date, about 1.6 million birds have died or been destroyed.
– Sequencing of virus from one of the fatal cases in Viet Nam reveals that all genes are of avian origin.

14 January
– WHO sends an urgent request for assistance to GOARN to identify experts to support the Vietnamese health authorities and the WHO office in Hanoi. Immediate objectives are to reduce the risk of transmission from birds to humans and to support health authorities in the epidemiological investigation and containment of human cases. Expertise is also requested to increase laboratory capacity, to advise on hospital infection control, and to strengthen surveillance for human cases.

15 January
– A fourth case of human infection with H5N1 is confirmed in Viet Nam. All four cases, which had been hospitalized in Hanoi, were fatal.

19 January
– A fifth fatal case of H5N1 infection is confirmed in Viet Nam, also in Hanoi.
– A single peregrine falcon is found dead near a residential development in Hong Kong. Testing begins immediately. Two days later, H5N1 is confirmed in samples taken from the bird.
– WHO staff and a GOARN international team arrive in Viet Nam. Members of the team are drawn from the Centers for Disease Control and Prevention (CDC), USA; the European Commission (DGAL – Ministère de l’agriculture, de l’alimentation, de la pêche et des affaires rurales, France); European Programme for Intervention Epidemiology Training (EPIET) Network; Health Protection Agency, UK; Institut de Vielle Sanitaire, France; Institut Pasteur Network, France; Institute for Infectious Disease Control (SMI), Sweden; National Institute of Infectious Diseases, Japan; RIVM, the Netherlands, and the Robert Koch Institute, Germany.

20 January
– Laboratories in the WHO Global Influenza Surveillance Network accelerate work needed to develop an H5N1 vaccine for humans.

22 January
– Network laboratories determine that H5N1 viruses in the current human and avian outbreaks are significantly different from H5N1 viruses in outbreaks in Hong Kong in 1997 and 2003, indicating that the virus has mutated.

23 January
– Authorities in Thailand report an outbreak of highly pathogenic avian influenza, caused by the H5N1 strain, at a farm in Suphanburi Province. This is the first time that highly pathogenic avian influenza has ever been reported in the country. Nearly 70,000 birds have died or been destroyed. Japan, the EU, and other major export markets immediately ban all Thai poultry products.
– The Ministry of Public Health in Thailand informs WHO of two laboratory confirmed cases of H5N1 infection in humans. The cases, from Suphanburi and Kanchanburi provinces, are young boys. Both are alive.
– Influenza network laboratories report that human H5N1 viruses from Viet Nam are resistant to one class of antiviral drugs, the M2 inhibitors, amantadine and rimantadine.

24 January
– Viet Nam reports two more cases of H5N1 infection in children hospitalized in Ho Chi Minh City – the first cases from the south. One child died, and the second remains hospitalized in critical condition. The country has now reported 7 cases, 6 of which were fatal.
– Viet Nam reports that the H5N1 outbreak in poultry has spread to 23 of the country’s 64 provinces. Nearly 3 million chickens have either died or been destroyed.
– Cambodia reports H5N1 in chickens in a farm near Phnom Penh.

25 January
– WHO staff and a GOARN international team, with support from Health Canada, arrive in Thailand.

26 January
– Authorities in Thailand report laboratory confirmation of the country’s third case, also in a young child. One of the two previously confirmed cases dies.

27 January
– Thailand’s third case, reported on 26 January, dies. Of the 3 cases, one remains alive.
– Viet Nam reports its 8th case. The child has fully recovered and been discharged from hospital.
– The Ministry of Health in China confirms the presence of highly pathogenic H5N1 avian influenza in poultry at a duck farm in the Guangxi Zhuang Autonomous Region in the south.
– Laos reports poultry deaths at a farm near the capital city of Vientiane. The report states that 2,700 hens in a flock of 3,000 have died. Initial tests identify H5. Arrangements are made to test for H5N1.
– Cambodia reports positive influenza A results from geese at a farm near Phnom Penh.

28 January
– Pakistan reports an outbreak of highly pathogenic avian influenza. Testing detects the H7 subtype. The report states that 1.7 million hens have either died or been destroyed.

30 January
– Chinese authorities confirm H5N1 infection in poultry at farms in an additional two provinces, Hunan and Hubei. Suspected outbreaks are reported in Anhui and Guangdong provinces and in Shanghai municipality.

1 February
– Viet Nam confirms two further cases, both fatal, in sisters, aged 23 and 30 years. Of the country’s 10 cases, 8 have died, one has recovered, and one remains hospitalized.

2 February
– Thailand reports its fourth confirmed case of H5N1 infection in a 58-year-old woman from Suphanburi Province, who died on 27 January. Of the country’s four cases, three have been fatal.
– Chinese authorities report that H5N1 infection is now confirmed or suspected in 10 of the country’s 31 provinces, autonomous regions, and municipalities.
– A WHO investigation of a family cluster in Thai Binh Province, Viet Nam, fails to reveal a specific event, such as contact with sick poultry, or an environmental source, to explain these cases and concludes that limited human-to-human is one possible explanation.
– Indonesia reports an outbreak of highly pathogenic avian influenza in poultry, subsequently confirmed as H5N1. This is the first time that highly pathogenic avian influenza has ever been reported in the country.

3 February
– Thailand’s one surviving case, reported on 23 January, dies. To date, Thailand has reported four cases, all fatal.
– Viet Nam reports an additional three cases, one fatal, all in young adults.
– Authorities in Viet Nam report that 52 of the country’s 64 provinces have been affected by H5N1 in poultry.
– Thai authorities estimate that around 26.9 million chickens have been culled nationwide, with slaughtering continuing in 7 provinces. Altogether, 36 of the country’s 76 provinces have been affected.
– Tests confirm that the poultry outbreaks in Indonesia are caused by H5N1. In 1995, highly pathogenic avian influenza was declared to be present throughout the country.

4 February
– Chinese authorities report the spread of H5N1 infection in poultry to farms in two additional provinces.
– In Vientiane, Laos, 17 out of 18 farms (including one duck farm) test positive for the H5 subtype.

5 February
– Viet Nam reports two further cases, both fatal, in young adults.
– Thailand confirms the country’s fifth case. The patient, a child, died on 2 February.
– In Thailand, 40 of the country’s 76 provinces have reported H5N1 disease in poultry.
– The Republic of Korea confirms H5N1 infection at an additional two farms in Asan, south of Seoul, suggesting that the epidemic in birds is not fully under control.

6 February
– A GOARN international team arrives in Cambodia. Members of the GOARN team are drawn from the Institut de Vielle Sanitaire, and the Institut Pasteur Network in France.
– China confirms further spread in poultry. Altogether, H5N1 infection is confirmed or suspected at farms in 13 of the country’s 31 administrative districts.
– In Viet Nam, 56 of the country’s 64 provinces are now affected by H5N1 disease in poultry.
– As part of the investigation of possible human-to-human transmission in a family cluster in Viet Nam, virus from one fatal confirmed case is fully sequenced. All genes are of avian origin. This finding does not, however, entirely rule out limited human-to-human transmission. If this occurred, the chain of transmission reached a dead end with the death or recovery of all family members in the cluster.

8 February
– US authorities report an outbreak of avian influenza at a farm in Delaware. H7 is detected in the initial tests. Further tests are initiated to determine if the H7 subtype is highly pathogenic. Some 12,000 birds are destroyed.
– OIE reports that half a million birds have been culled at 9 farms in China where H5N1 infection has been confirmed.

9 February
– Viet Nam reports 3 additional cases, two of which were fatal.
– The total number of cases in the two affected countries, Viet Nam and Thailand, is now 23 cases, of which 18 were fatal.
– In Viet Nam, 57 of the country’s 64 provinces have been affected by H5N1 in poultry. Around 27 million birds have died or been destroyed.

10 February
– Chinese authorities report a suspected H5N1 outbreak at a chicken farm in Tianjin Municipality. Spread to additional farms within other provinces is also reported. Altogether, H5N1 infection is suspected or confirmed on 39 farms in 14 of the country’s 31 provinces, autonomous regions, and municipalities. Of the outbreaks at 39 farms, 19 are confirmed as caused by H5N1.
– Avian influenza is detected at a second farm in Delaware. Some 72,000 birds are destroyed. Japan, China, Poland, Malaysia, Singapore, and the Republic of Korea ban poultry imports from the US.

11 February
– In the investigation of possible human-to-human transmission in Viet Nam, results from the analysis of virus isolated from the second sister in the family cluster show that the virus is of avian origin and contains no human influenza genes. – WHO issues guidelines for global surveillance aimed at monitoring spread of H5N1 infection in human and animal populations.
– The number of farms in China with confirmed H5N1 outbreaks increases from 19 to 23.

12 February
– Thailand confirms its sixth case, a 13-year-old boy.
– Viet Nam confirms its 19th case, which was fatal in a 19-year-old man who had been hospitalized in Ho Chi Minh City.
– The total number of confirmed cases in these two countries combined is 25, of which 19 have been fatal.
– The first clinical and epidemiological data on 10 cases in the Viet Nam outbreak is made public by WHO.

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