America’s Centres for Disease Control and Prevention (CDC), on Wednesday, May 22, confirmed a new human infection with the H5 avian influenza virus (avian flu), a pathogen with pandemic potential that has recently spread rapidly among dairy cows in the United States, according to The Economist. This is the second identified human case linked to the cow outbreak. Both cases involve farm workers who likely contracted the virus through contact with infected animals, exhibiting only mild symptoms. Although there is no evidence of human-to-human transmission, America’s public health authorities remain on high alert. Half of the national pandemic stockpile of the H5N1 vaccine is being prepared for deployment.
Influenza viruses infect many species and occasionally cross over to infect a new host, often with severe consequences. H5N1, an avian influenza virus (avian flu), has crossed into various bird and some mammalian species and is considered a potential pandemic threat due to the lack of human immunity. Since its initial detection in geese in China nearly three decades ago, around 900 human infections have been recorded worldwide, typically from contact with infected poultry or other birds. Approximately half of these cases were fatal. However, mild or asymptomatic infections likely went undetected, suggesting the true fatality rate may be lower.
In 2022, H5N1 (avian flu) began spreading more extensively among wild bird species, which transported the virus globally, infecting various wild mammals, farmed poultry, and mink. The virus is highly lethal in poultry, prompting farms in Europe, America, and Asia to cull hundreds of millions of birds to contain its spread.
This spring, H5N1 appeared in dairy cows on a farm in Texas and has since been detected in dairy herds in at least nine states. In early May, the Food and Drug Administration (FDA) found that about 20 per cent of milk samples from store shelves across the United States contained H5N1 (which is killed by pasteurisation), indicating a broader spread among dairy cows than initial animal testing confirmed.
Farmers have been reluctant to report outbreaks or test cows due to the potential financial loss. Surveillance for infections in farm workers has also been insufficient, exacerbated by many workers being undocumented immigrants who do not speak English and rely on daily wages. Consequently, reaching them with information and convincing them to get tested has been challenging. As of 22nd May, only 40 individuals with suspected H5N1 (avian flu) had been tested.
Scientists are piecing together imperfect data to understand how H5N1 is evolving. An American scientific consortium is now searching for H5N1 in wastewater, although this method can only indicate high virus circulation areas without identifying specific sources like cows, humans, discarded milk, or infected wild birds shedding the virus into sewers.
Jennifer Nuzzo, an epidemiologist at Brown University, emphasises that “if this were spreading human-to-human, we’d know.” The immediate health concern is that farm workers are being infected through exposure to sick animals, with little being done to halt the spread among cows.
Despite limited testing, it is somewhat reassuring that only two human cases related to the cow outbreak have been confirmed, given the extensive contact between farm workers and infected cows. Michael Worobey, an evolutionary biologist at the University of Arizona, notes that milk from infected cows contains high levels of H5N1, so exposure at milking stations could lead to human infections. Serious symptoms would likely have brought more cases to medical attention by now.
The two infected farm workers exhibited only conjunctivitis (commonly known as “pink eye”). Human eye cells have specific receptors similar to those in bird cells, allowing H5N1 to infect without the need for specialised mutations. Human lung cells also have these receptors, explaining severe lung infections in past bird-to-human transmission cases. However, human upper respiratory tract cells lack these receptors, meaning the virus would need genetic mutations to spread easily between people.
So far, genomic analysis of H5N1 samples from American farms has not detected any of these critical mutations. A nasal swab from one infected farm worker was negative, with only the eye sample testing positive.
The situation in America is troubling. The widespread presence of H5N1 in mammals with frequent human contact increases the risk of a human-adapted version emerging. As the virus mutates among cows, a human-infecting mutation could arise. Additionally, a recombinant version of H5N1 could emerge if a person is co-infected with both cow H5N1 and a seasonal flu virus, allowing genetic swapping to produce a highly contagious human strain.
While future developments are unpredictable, the current outbreak in America does not bode well for preventing a future pandemic. Effective surveillance systems to detect, track, and limit the spread of new pathogens in farmed animals are crucial. Without such measures, the next pandemic could originate as easily in Texas as in Wuhan, according to The Economist.
The Nigerian government has introduced a Contactless Passport Application System (CONPAS) for Nigerians residing in… Read More
Vacancy: Manager, Operations Location: Douala, Cameroon Employment Type: Full-Time, Permanent Department: Operations Company Overview IHS… Read More
IHS Towers is one of the world's largest independent owners, operators, and developers of shared… Read More
About the company FairMoney is a pioneering mobile banking institution specializing in extending credit to… Read More
In a controversial move likely to deepen tensions between Washington and Pretoria, US President Donald… Read More
The Company Our client is a leading Road Asset Management company dedicated to optimising infrastructure… Read More