Human emerging respiratory pathogens bulletin: Issue 86, February 2024

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 February 2024, the following human cases have been reported (Figure 1):

• Three new human cases of avian influenza A(H5N1)
• One new human case of avian influenza A(H9N2)
• Two new human cases of swine origin influenza A(H1N1)v
• One new human case of MERS-CoV

Figure 1 - Text description

• Three (3) A(H5N1) cases were reported in Cambodia.
• One (1) A(H9N2) case was reported in China.
• Two (2) A(H1N1)v cases were reported in Brazil and Spain.

Avian influenza updates

Avian influenza A(H5N1)

Three new human cases of avian influenza A(H5N1) were reported in February 2024 from Cambodia.

The first case was a 9-year-old boy from Kapo 1 Village, Or Russey Commune, Kratie City, Kratie Province, Cambodia. The case had developed symptoms of fever, shortness of breath, cough and fainting on January 31, 2024, was hospitalized on February 5, 2024, and died on February 8, 2024.

The second case was a 16-year-old male, identified on February 11, 2024 as a close contact of the 9-year-old boy, the first case. The case was asymptomatic however, he was admitted to hospital for monitoring and treatment and was in isolation at home at the time of last report.

The first (9-year-old boy) and second (16-year-old boy) cases are siblings; dead poultry was brought from the household of the first case to the household of the second case, and both siblings were exposed. The chicken was cooked and consumed by both siblings. Based on available information, human-to-human transmission cannot be excluded; however, no further suspected cases or evidence of sustained human-to-human transmission was found.

The third case was a 17-year-old female residing in Kampot province, Cambodia. The case developed fever, cough, tiredness, and difficulty breathing on an unknown date. At the time of report, the case was in intensive care. There was reported exposure to 7 dead chickens approximately 5 days prior to illness onset.

In 2024, 5 human cases of avian influenza A(H5N1) have been detected worldwide, all from Cambodia. Since 2022, 24 human cases of A(H5N1) have been reported worldwide (2022: n=6, 2023: n=13, 2024: n=5) in Cambodia (11), Chile (1), China (2), Ecuador (1), Spain (2), United Kingdom (5), United States (1), Vietnam (1) (Figure 2). Of these cases, 13 (including 1 death) belonged to clade 2.3.4.4b, 9 cases (including 5 deaths) all from Cambodia belonged to clade 2.3.2.1c and 2 are pending.

The A(H5N1) clade 2.3.2.1c detected in Cambodia is different from the clade A(H5N1) 2.3.4.4b that is predominantly circulating worldwide including in Canada. Since the emergence of A(H5N1) in humans in 1997, 905 human cases of A(H5N1) have been reported globally, with a CFR of 52% (Figure 3). In Canada, A(H5N1) detections associated with the current 2021-2024 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

• Eleven (11) cases were reported out of Cambodia.
• Five (5) cases were reported out of the United Kingdom.
• Two (2) cases were reported out of China.
• Two (2) cases were reported out of Spain.
• One (1) case was reported out of Chile.
• One (1) case was reported out of Ecuador.
• One (1) case was reported out of the United States of America.
• One (1) case was reported out of Vietnam.

Figure 3 - Text description

Temporal distribution of human cases of A(H5N1) influenza reported, globally, by year, January 1, 1997 to February 29, 2024 (n=905).

	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
2024	5	1	4

Avian influenza A(H5N6)

The most recent human case of avian influenza A(H5N6) was reported in January 2024 from China.

In 2024, 1 human case of avian influenza A(H5N6) was detected worldwide. In 2023, 6 human cases of avian influenza A(H5N6) were detected, all in China. Since January 2021, 64 cases of avian influenza A(H5N6) have been reported globally (2021: n=32, 2022: n=25, 2023: n=5, 2024: n=1) (Figure 4); the majority of cases (63) were reported from China and one case was reported from Lao PDR (Figure 4). Since the emergence of this virus in 2014, a total of 90 laboratory-confirmed human cases of avian influenza A(H5N6), including at least 35 deaths, have been reported globally (CFR: 39%). No cases have been reported in Canada.

Figure 4 - Text description

Temporal distribution of human cases of A(H5N6) influenza reported, globally, by month, January 1, 2021 to February 29, 2024 (n=64).

	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
2024	Jan	1
	Feb	0

Avian influenza A(H9N2)

One new human case of avian influenza A(H9N2) was reported in February 2024 from China.

The case was a 22 month-old girl who developed symptoms of fever and cough with sputum on February 15, 2024 and visited a medical facility the next day with no required hospitalization. Infection with A(H9N2) was confirmed on February 23, 2024 and the virus was found to be sensitive to the antiviral Tamiflu. The case has since recovered. The case visited Zhongshan, Guangdong Province during the incubation period. She had no reported direct contact with poultry recently, had not consumed undercooked poultry, nor had any contact with patients. One household contact developed a sore throat on February 17, 2024, although this symptom subsided after taking medication and tested negative for Influenza A. The case's other household contacts are asymptomatic.

This case marks the first reported human case of avian influenza A(H9N2) in 2024. In 2023, a total of 15 human cases of avian influenza A(H9N2) were reported globally, all in China. Since the emergence of avian influenza A(H9N2) in the human population in 1998, 123 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

Two new human cases of swine origin influenza A(H1N1)v were reported in February 2024 from Brazil and Spain.

The first case was a 49-year old male with underlying conditions from Toledo, Paraná, Brazil. The case developed symptoms of fever, headache, cough, adynamia, odynophagia, dyspnea and asthenia on December 12, 2023, was hospitalized on December 16, 2023 and was discharged after fully recovering on December 18, 2023. The case did not receive antiviral treatment nor the seasonal influenza vaccine in 2023 and has no history of exposure to pigs. No close contacts of the case were identified. On January 15, 2024, the results confirmed infection with A(H1N1)v. According to the sequencing results, reported by the WHO "the virus shares 99% similarity with the A/Paraná/ virus 20675/2022 (A/H1N1 pdm09) previously detected in the city of Toledo-Paraná in October 2022. The segments PB2, PB1, PA, NA, and MP corresponded to the virus A/Paraná/10835/2021 (A/H1N1 pdm09) also reported in the city of Toledo and the NP and NS segments corresponded to the virus A/Paraná/44706/2022 (A/H3N2v) reported in the city of Santa Helena, also in the state of Paraná. A second HA result, however, showed 95% similarity to viruses collected from Brazil's swine in March of 2015 (A/swine/Brazil/EMBRAPA-35152/2015)" (WHO).

The second case was a 33-year old male pig farm worker with no underlying conditions from Catalonia, Lleida, Spain. The case developed symptoms of cough with muco-purulent expectoration, fever, malaise, and myalgia on November 25, 2023 and was diagnosed with bronchitis. The case was treated with bronchodilators and oral corticosteroids but did not receive antiviral treatment. On December 14, 2023, the results confirmed infection with A(H1N1)v catalogued as A/Catalonia/NSAV198289092/2023 (GISAID accession: EPI_ISL_18782577). A sample was sent for confirmation to the National Institute of Microbiology and the virus isolate will be shared with the WHO Collaborating Centre, results are not yet available. The case has since recovered. To date, no new cases have been detected among close contacts or co-workers on the farm through the epidemiological investigation.

In 2024, 2 human cases of swine origin influenza A(H1N1)v have been detected worldwide. There have been 5 human A(H1N1)v cases reported worldwide in 2023 in Brazil (1), China (2), Spain (1) and Switzerland (1). A total of 48 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).

To date, no human cases of swine origin influenza A(H1N2)v have been reported in 2024. In 2023, 4 human swine origin influenza A(H1N2)v cases were reported worldwide in Taiwan (1), the UK (1), and the United States (2). 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.

To date, no human cases of swine origin influenza A(H3N2)v have been reported worldwide in 2024. Excluding the reported case of A(H3NX)v in the United States (1), no cases of swine origin influenza A(H3N2)v were detected in 2023. 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

One new human case and details on three previously reported cases of MERS-CoV were reported in February 2024 from Saudi Arabia.

The first case was a 59-year-old female Saudi national, non-healthcare worker (housewife), in Eastern Region. She developed a fever, cough, sore throat, and shortness of breath on September 30, 2023. She was admitted to hospital on October 5, 2023, and was diagnosed with pneumonia. The case was discharged on November 12, 2023. She had multiple comorbidities: diabetes mellitus, asthma, and leukemia. There was no clear history of exposure to known risk factors. Follow-up for 16 household contacts and 29 healthcare workers was completed, and no secondary cases were identified.

The second case was a 93-year-old female Saudi national, non-healthcare worker, living in Qassim Region. She developed a fever, sore throat, confusion, and decreased consciousness on September 15, 2023. The case was admitted to hospital in Qaseem on September 23, 2023, and referred to a hospital in Riyadh on September 25, 2023, for treatment of her chronic conditions and was diagnosed with pneumonia. She was admitted to the intensive care unit (ICU) in critical condition on September 25, 2023. The case died on October 19, 2023. She had a history of diabetes mellitus and liver disease. There was no clear history of exposure to known risk factors. Follow-up for 5 household contacts and 43 healthcare workers was completed, with no secondary cases identified.

The third case was a 79-year-old male, Saudi national, non-healthcare worker living in Riyadh Region. He developed a fever, cough, and shortness of breath on September 27, 2023. He was hospitalized and admitted to the ICU on September 29, 2023, and was diagnosed with pneumonia. The case was discharged from hospital on November 12, 2023. Comorbidities included diabetes mellitus and chronic obstructive pulmonary disease. The case had no direct contact with camels, but he did have contact with his brother, who is a camel owner. The case's brother was asymptomatic and tested negative for MERS-CoV (however, this test was performed more than 10 days after the positive case confirmation). In total, 5 household contacts and 14 healthcare workers completed follow-up, with no secondary cases identified. The camels owned by the case's brother were asymptomatic and no laboratory results were shared.

The fourth case was a 66-year-old male Saudi national, non-healthcare worker living in Riyadh Region. He developed a fever, cough, and shortness of breath on October 26, 2023. The case was admitted to the ICU in Riyadh on November 8, 2023, and was diagnosed with pneumonia. He died on December 24, 2023. The case had asthma as a comorbidity. He had a history of direct contact with camels as he was a camel owner. In total, a follow-up of 16 household contacts and 34 healthcare workers was completed, with no secondary cases identified. The camels were asymptomatic, and no laboratory results were shared.

To date, one new human case of MERS-CoV and one new fatality were reported in 2024. In 2023, 10 cases of MERS-CoV were reported in Oman (1), Saudi Arabia (8), and the United Arab Emirates (1). According to the WHO, 2,609 laboratory-confirmed cases of MERS-CoV, including 939 deaths, have been reported globally since reporting began in 2012 (CFR: 36%) (Figure 5). No cases have ever been reported in Canada.

Figure 5 - Text description

Temporal distribution of human cases of MERS-CoV reported to the WHO, globally, by month and year, January 1, 2019 to February 29, 2024 (n=330).

		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
2024	Jan	0	0
	Feb	1	0