H5N1-infected teenager now in ‘critical condition’ say Canadian doctors

An image provided by the US Centers for Disease Control and the National Institute of Allergy and Infectious Diseases shows a colourised transmission electron micrograph of H5N1 virus particles grown in a lab.

• A Canadian teenager is in critical condition with suspected H5N1 bird flu, health authorities said.
• The teen developed symptoms on November 2 and tested positive on November 8.
• Over 40 contacts have been tested, with some offered Tamiflu, but no infections found.

A Canadian teenager hospitalised with suspected H5N1 bird flu is now in critical condition, health authorities said on Tuesday.

The patient, Canada’s first presumed human case of H5N1, was previously healthy and had no underlying conditions, a health official confirmed in a press conference.

The teenager first developed symptoms on November 2 and tested positive for bird flu on November 8, when they were admitted to intensive care.

While the exact strain is yet to be determined, authorities have presumed the virus is H5N1 – the strain that is currently circulating in US dairy cattle.

It has infected more than 40 people this year, primarily in dairy and poultry workers across the US.

The Canadian patient first developed conjunctivitis, fever and coughing, all of which are consistent with the relatively mild symptoms reported by dairy and poultry workers infected with the virus in the US.

However, unlike those cases, the teen quickly developed acute respiratory distress syndrome, a serious lung condition that causes low blood oxygen and can be fatal.

“It just reminds us that in young people this is a virus that can progress and cause quite severe illness and the deterioration was quite rapid,” health officer Bonnie Henry told reporters.

They have been treated with “multiple medications” after consulting with a team of doctors in the US, Henry said.

The source of infection has yet to be identified and investigations are ongoing.

The teenager had no farm exposure, but had been exposed to dogs, cats, and reptiles, Henry said. One dog was sick, although tested negative for H5N1.

In British Columbia, H5N1 has been detected in wild birds, on poultry farms and among small wild mammals, including skunks and foxes. However, unlike in the US, there have been no cases reported in dairy cattle and no evidence of avian influenza in samples of milk in Canada.

More than 40 of the teenager’s contacts have been identified and tested, although there is no evidence any have been infected with the virus. Some have been preventively offered Tamiflu, a prescription medicine used to treat influenza.

H5N1 has historically had a very high death rate of around 55%, although recent cases in the US have been mild.

Between 2003 and October 2024, the World Health Organization recorded 921 cases of confirmed H5N1 influenza, 464 of which have died.