Human emerging respiratory pathogens bulletin: Issue 84, December 2023

The Human Emerging Respiratory Pathogens (HERP) Bulletin is a monthly publication developed by the Public Health Agency of Canada (PHAC)'s Centre for Emerging and Respiratory Infections and Pandemic Preparedness (CERIPP). The HERP Bulletin serves as a mechanism for information sharing on summary surveillance indicators of global public health events affecting humans in the field of emerging respiratory pathogens. This includes pathogens such as novel influenzas (both avian and swine-origin), Middle East Respiratory Syndrome Coronavirus (MERS-CoV), and other ad-hoc emerging respiratory pathogens.

Monthly Highlights

During the month of December 2023, the following human cases have been reported:

• One new human case of avian influenza A(H5N6)
• Two new human cases of avian influenza A(H9N2)
• One new human case of swine origin influenza A(H1N1)v
• Three new human cases of MERS-CoV

Figure 1 - Text description

• One (1) A(H5N6) case was reported in China.
• Two (2) A(H9N2) cases were reported in China.
• One (1) A(H1N1)v case was reported in Switzerland.

Avian influenza updates

Avian influenza A(H5N1)

The most recent human cases of avian influenza A(H5N1) were reported in November 2023 from Cambodia.

In 2023, 13 human cases of avian influenza A(H5N1) have been detected worldwide. This case count for 2023 represents an increase compared to the 6 reported human cases from January 2022 to December 2022. Since 2022, 19 human cases of A(H5N1) have been reported worldwide (2022: n=6, 2023: n=13) in Cambodia (6), Chile (1), China (2), Ecuador (1), Spain (2), United Kingdom (5), United States (1), Vietnam (1). Of these cases, 13 belonged to clade 2.3.4.4b and 6 belonged to clade 2.3.2.1c (Cambodia). Since the emergence of A(H5N1) in humans in 1997, 900 human cases of A(H5N1) have been reported globally, with a CFR of 52%.

In Canada, A(H5N1) detections associated with the current 2021-2023 A(H5N1) clade 2.3.4.4b epizootic have been reported in domestic, backyard, and wild bird populations, as well as other animal species. No domestically acquired human A(H5N1) infections have been reported in Canada. In 2014, Canada (Alberta) reported a single fatal case of A(H5N1) in a resident returning from travel in China.

Figure 2 - Text description

Year	Number of Cases	Deaths	Survived
1997	18	6	12
1998	0	0	0
1999	0	0	0
2000	0	0	0
2001	0	0	0
2002	0	0	0
2003	4	4	0
2004	46	32	14
2005	98	43	55
2006	115	79	36
2007	88	59	29
2008	44	33	11
2009	73	32	41
2010	48	24	24
2011	62	34	28
2012	32	20	12
2013	39	25	14
2014	52	22	30
2015	145	42	103
2016	10	3	7
2017	4	2	2
2018	0	0	0
2019	1	1	0
2020	1	0	1
2021	2	1	1
2022	5	1	4
2023	13	4	9

Avian influenza A(H5N6)

One new human case of A(H5N6) was reported in December 2023 from China.

The case is a 33-year-old female farmer from Bazhong city, Sichuan province, China. She had an illness onset date of October 20, 2023, was hospitalized with severe pneumonia on October 22, 2023 and died on November 14, 2023. She had hypothyroidism as a comorbidity and had visited a live poultry market prior to illness onset.

At the time of last report no family members have developed symptoms. Samples from close contacts tested negative for influenza and environmental samples tested negative.

In 2023, 6 human cases of avian influenza A(H5N6) have been detected, all in China. This case count for 2023 represents a decrease compared to the 25 reported human cases from January 2022 to December 2022. Since January 2021, 63 cases of avian influenza A(H5N6) have been reported globally (32 cases were reported in 2021, 25 cases in 2022 and 5 cases in 2023) (Figure 4); the majority of cases (62) were reported from China and one case was reported from Lao PDR (Figure 3). Since the emergence of this virus in 2014, a total of 89 laboratory-confirmed human cases of avian influenza A(H5N6), including at least 34 deaths, have been reported globally (CFR: 38%). No cases have been reported in Canada.

Figure 3 - Text description

Year	Month	Cases
2021	Jan	1
	Feb	2
	Mar	2
	Apr	0
	May	0
	June	1
	July	4
	Aug	6
	Sep	6
	Oct	4
	Nov	0
	Dec	6
2022	Jan	8
	Feb	6
	Mar	3
	Apr	3
	May	1
	June	1
	July	0
	August	0
	Sep	1
	Oct	1
	Nov	0
	Dec	1
2023	Jan	0
	Feb	0
	Mar	1
	Apr	0
	May	1
	June	0
	July	1
	August	2
	Sep	0
	Oct	0
	Nov	0
	Dec	1

Figure 4 - Text description

• Four cases were reported out of Yongzhou, Hunan Province, People's Republic of China.
• Four cases were reported out of Guilin, Guangxi Zhuang Autonomous Region, People's Republic of China.
• Three cases were reported out of Huizhou, Guangdong Province, People's Republic of China.
• Three cases were reported out of Liuzhou, Guangxi Zhuang Autonomous Region, People's Republic of China.
• Two cases were reported out of Baise, Guangxi Zhuang Autonomous Region, People's Republic of China.
• Two cases were reported out of Bazhong, Sichuan Province, People's Republic of China.
• Two cases were reported out of Chengdu, Sichuan Province, People's Republic of China.
• Two cases were reported out of Chenzhou, Hunan Province, People's Republic of China.
• Two cases were reported out of Dongguan, Guangdong Province, People's Republic of China.
• Two cases were reported out of Guangxi Zhuang Autonomous Region, People's Republic of China.
• Two cases were reported out of Hechi, Guangxi Zhuang Autonomous Region, People's Republic of China.
• Two cases were reported out of Hengyang, Hunan Province, People's Republic of China.
• Two cases were reported out of Jiangxi Province, People's Republic of China.
• Two cases were reported out of Sichuan Province, People's Republic of China.
• Two cases were reported out of Tongnan District, Chongqing Municipality, People's Republic of China.
• Two cases were reported out of Zhenjiang, Jiangsu Province, People's Republic of China.
• One case was reported out of Anhui Province, People's Republic of China.
• One case was reported out of Changde, Hunan Province, People's Republic of China.
• One case was reported out of Deyang City, Sichuan Province, People's Republic of China.
• One case was reported out of Fuzhou, Fujian Province, People's Republic of China.
• One case was reported out of Ganzhou City, Jiangxi Province, People's Republic of China.
• One case was reported out of Guizhou Province, People's Republic of China.
• One case was reported out of Hangzhou, Zhejiang Province, People's Republic of China.
• One case was reported out of Kaijiang County, Sichuan Province, People's Republic of China.
• One case was reported out of Laibin, Guangxi Zhuang Autonomous Region, People's Republic of China.
• One case was reported out of Langzhong City, Sichuan Province, People's Republic of China.
• One case was reported out of Luang Prabang Province, Lao People's Democratic Republic (the).
• One case was reported out of Nanning, Guangxi Zhuang Autonomous Region, People's Republic of China.
• One case was reported out of Puyang City, Henan Province, People's Republic of China.
• One case was reported out of Xuanhan County, Sichuan Province, People's Republic of China.
• One case was reported out of Yangzhou, Jiangsu Province, People's Republic of China.
• One case was reported out of Yibin, Sichuan Province, People's Republic of China.
• One case was reported out of Yongchuan District, Chongqing Municipality, People's Republic of China.
• One case was reported out of Zhejiang Province, People's Republic of China.
• One case was reported out of Zigong City, Sichuan Province, People's Republic of China.
• One case was reported out of Nanning, Guangxi Province, People's Republic of China.
• One case was reported out of Guangxi Zhuang Autonomous Region, People's Republic of China.
• One case was reported out of Changsa, Hunan Province, People's Republic of China.
• One case was reported out of Qingyuan, Guangdong Province, People's Republic of China.
• Two cases were reported out of Sichuan Province, People's Republic of China.

Avian influenza A(H9N2)

Two new human cases of avian influenza A(H9N2) were reported in December 2023 from China.

The first (index) case was a 1-year-old male from Sichuan province with an illness onset date of November 14, 2023. He experienced mild illness and was not hospitalized. This case was detected through influenza-like-illness surveillance.

The second case was a 74-year-old female from Sichuan province who had an illness onset date of November 5, 2023. She developed mild illness and was not hospitalized. This case was detected during tracing of close contacts and testing for the index case. The cases were neighbours.

Both cases had contact to sick backyard chickens prior to illness onset. 12 samples were collected from close contacts, 11 tested negative and one tested positive (the second case described above) for A(H9N2). and environmental samples from around the cases' homes tested positive for A(H9).

Currently available information indicates that there is no epidemiological link between the cases, and both were infected following exposure to infected backyard poultry.

In 2023, a total of 15 human cases of avian influenza A(H9N2) have been reported globally, all in China. This case count for 2023 represents a decrease compared to the 21 reported human cases from January 2022 to December 2022. Since the emergence of this virus in the human population in 1998, 122 cases have been reported worldwide, with a CFR of 2%. No cases have been reported in Canada.

Swine influenza updates

Swine origin influenza A(H1N1)v

One new case of swine origin influenza A(H1N1)v was reported in December 2023 from Switzerland.

The case is a male farm worker living in Lucerne, Switzerland with illness onset of November 14, 2023 and was detected on November 27, 2023 as part of a surveillance project on influenza at the human-animal interface. The case experienced mild symptoms and has since recovered. The case had direct occupational exposure to swine prior to illness onset. Pigs on the swine farm tested positive for swine influenza A. Sequencing results indicate that this virus is an A(H1N1)v strain of clade 1C.2.2. Further viral characterization is ongoing. This strain has been detected in a human in Germany in 2022 as well as in the swine population in Switzerland and other European countries (France, Germany, United Kingdom) within the last two years. Four household contacts were identified with two reporting symptoms of illness. All four household contacts were tested by RT-PCR on December 4, 2023 and were negative for influenza A and influenza B.

There have been 5 human A(H1N1)v cases reported worldwide in 2023 in Brazil (1), China (2), Spain (1) and Switzerland (1). This case count for 2023 represents a slight increase compared the 4 reported human cases from January 2022 to December 2022. A total of 46 human cases of A(H1N1)v have been reported globally since 2005, with a 2% CFR. Two A(H1N1)v detections have been reported in Canadian residents since reporting began in 2005, with the first case reported in Ontario in September 2012 and the second case reported in Manitoba in April 2021 (see HERP Bulletin no 52).

Swine origin influenza A(H1N2)v

The most recent human case of swine origin influenza A(H1N2)v was reported in November 2023 from the United Kingdom (UK).

There have been 4 human swine origin influenza A(H1N2)v cases reported worldwide in 2023 in Taiwan (1), the UK (1), and the United States (2). This case count for 2023 represents a decrease compared to the 8 reported human cases from January 2022 to December 2022. A total of 50 human cases of swine origin influenza A(H1N2)v have been reported globally since 2005, with a 0% CFR. Three swine origin influenza A(H1N2)v detections have been reported in Canadian residents since reporting began in 2005. The first case was reported in Alberta in October 2020 (see HERP Bulletin no 46), the second case was reported in Manitoba in April 2021 (see HERP Bulletin no 52) and the latest case in Canada was reported in November 2021 in Manitoba (see HERP Bulletin no 59).

Swine origin influenza A(H3N2/H3NX)v

The most recent human case of swine origin influenza A(H3N2)v was reported in November 2022 from the United States. The most recent human case of swine origin influenza A(H3NX)v was reported in August 2023 from the United States.

Excluding the reported case of A(H3NX)v in the United States (1), no cases of swine origin influenza A(H3N2)v have been detected in 2023. This case count for 2023 represents a decrease compared to the 5 reported human cases from January 2022 to December 2022. Globally, 446 swine origin influenza A(H3N2)v cases have been reported since 2005, with <1% CFR. Two swine origin influenza A(H3N2)v detections have been reported in Canadian residents since reporting began in 2005, with the latest case reported in June 2021 (see HERP Bulletin no 54).

Middle East respiratory syndrome coronavirus (MERS-CoV) update

The most recent human cases of MERS-CoV were reported in November 2023 from Saudi Arabia.

The Food and Agriculture Organization (FAO) of the United Nations reported three new Middle-East respiratory syndrome coronavirus (MERS-CoV) cases and one fatality that were reported from Saudi Arabia between October 19 – November 16. 2023. No additional case details were reported.

In 2023, 10 cases of MERS-CoV were reported in Oman (1), Saudi Arabia (8), and the United Arab Emirates (1). This case count for 2023 represents an increase compared to the 7 reported human cases from January 2022 to December 2022 but is lower than the yearly average case count reported within the past three years. According to the WHO, 2,608 laboratory-confirmed cases of MERS-CoV, including 938 deaths, have been reported globally since reporting began in 2012 (CFR: 36%). No cases have ever been reported in Canada.

Figure 5 - Text description

Year	Month	Deaths	Survived
2019	Jan	5	14
	Feb	14	62
	Mar	3	26
	Apr	11	11
	May	4	10
	June	1	6
	July	4	5
	Aug	1	5
	Sep	1	3
	Oct	6	8
	Nov	2	10
	Dec	3	2
2020	Jan	5	15
	Feb	5	14
	Mar	5	10
	Apr	0	2
	May	5	2
	June	0	0
	July	0	0
	Aug	0	0
	Sep	0	0
	Oct	0	0
	Nov	1	3
	Dec	0	3
2021	Jan	0	0
	Feb	3	3
	Mar	1	1
	Apr	0	0
	May	1	0
	June	0	1
	July	0	2
	Aug	1	0
	Sep	0	0
	Oct	0	1
	Nov	0	0
	Dec	3	0
2022	Jan	0	0
	Feb	0	0
	Mar	0	1
	Apr	1	0
	May	2	2
	June	0	0
	July	0	0
	August	0	0
	Sep	0	0
	Oct	0	0
	Nov	41	4
	Dec	0	1
2023	Jan	0	2
	Feb	0	0
	Mar	1	1
	Apr	0	0
	May	0	0
	June	0	0
	July	0	1
	August	2	1
	Sep	0	0
	Oct	0	0
	Nov	1	2
	Dec	0	0