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| Transmission electron micrograph of bird flu virus particles (orange) in kidney cells (green). (NIAID/Flickr/CC BY 2.0) |
The new case brings the total number of infections in the United States during the current 2024 outbreak to 61, as California declared an emergency in order to ramp up its response.
Prior patients experienced mild symptoms and recovered at home. But the severity of the Louisiana case has heightened alarm, echoing similar cases worldwide. Last month, a teenager in Canada was also hospitalized with a severe case of bird flu.
According to the US Centers for Disease Control and Prevention (CDC), the Louisiana patient was exposed to sick and dead birds in backyard flocks.
"The patient is experiencing severe respiratory illness related to H5N1 infection and is currently hospitalized in critical condition," the Louisiana health department said in a statement to AFP, adding the person has underlying medical conditions and is over the age of 65.
"Over the 20-plus years of global experience with this virus, H5 infection has previously been associated with severe illness in other countries, including illnesses that resulted in death in up to 50 percent of cases," Demetre Daskalakis, a senior CDC official told reporters on a call.
"The demonstrated potential for this virus to cause severe illness in people continues to highlight the importance of the joint… US federal response," he added.
Meanwhile the most populous US state California announced a state of emergency.
"This proclamation is a targeted action to ensure government agencies have the resources and flexibility they need to respond quickly to this outbreak," Governor Gavin Newsom said in a statement, vowing to expand the state's monitoring system and support the agriculture sector.
Mounting concerns
The Louisiana case was confirmed last Friday, according to the CDC. Genetic sequencing revealed that the H5N1 virus in the patient belonged to the D1.1 genotype.
This genotype has recently been detected in wild birds and poultry in the United States, and in human cases reported in Washington state and in the Canadian case, in British Columbia province.
The D1.1 genotype differs from the B3.13 genotype, which has been identified in dairy cows, some poultry outbreaks, and human cases with mild symptoms such as conjunctivitis.
A handful of US cases have had no known animal source of infection, including a case in Delaware, the CDC reported on Wednesday.
Rebecca Christofferson, a scientist at Louisiana State University, told AFP that the lack of robust surveillance makes it uncertain whether more animal-to-human spillovers are going undetected or if asymptomatic human-to-human transmission is occurring.
"I'm not panicking yet," she said, while emphasizing the need for increased vigilance.
But Meg Schaeffer, an epidemiologist at the US-based SAS Institute, told AFP recently there were now several factors suggesting that "avian flu is knocking on our door and could start a new pandemic any day."
Experimental vaccine
The US has stockpiled bird flu vaccines in preparation for potential human transmission, and on Wednesday, a new study revealed promising results for an experimental mRNA vaccine that successfully protected ferrets from the virus.
The current US outbreak of the flu – technically the Highly Pathogenic Avian Influenza, or H5N1 bird flu – was first reported in March in dairy cows.
US cases have included a young child in California, reported last month.
Compounding concerns is the possible role of raw milk as a vector for transmission.
The US Department of Agriculture issued a new federal order requiring that raw milk samples be shared on request from any dairy farm and milk transporter, and mandating that any samples testing positive for bird flu be reported to federal authorities.
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