A new strain of bird flu has jumped to humans in an event that has “potentially major consequences for public health”, the World Health Organization has warned.
Officials say a 59-year-old man in Mexico died after a seven-day illness in which he suffered from fever, shortness of breath, diarrhea and nausea.
Tests showed he was infected with a strain of bird flu called H5N2, marking the first time this type had ever been detected in humans.
The patient had no history of exposure to poultry or other animals. It is currently unclear how he became infected.
But officials said the risk to the public is “low” because the patient had underlying health conditions. It was not clear whether the disease had been spread to others.
However, they warned in an alert released today that ‘a human infection caused by a novel [bird flu virus] is an event with a potentially major impact on public health.”
The patient, from Mexico City, became unwell on April 17 but waited a week before seeking hospital care.
However, he died on the same day as his admission due to the ‘complications of his condition’.
PCR tests conducted on April 24 revealed that he had been infected with a flu virus, and later tests confirmed that the patient had H5N2.
Officials tested 17 people who came into close contact with the patient at the hospital, including one person who reported a runny nose. All tested negative.
Twelve people living near the patient’s home in Mexico City – including seven with symptoms of the illness – were also tested for bird flu, although all tested negative.
Officials are now conducting blood tests to screen for antibodies to the virus, which would show whether someone had had a previous infection.
The source of the infection has yet to be determined, although several flocks of poultry – which can carry H5N2 – have recently tested positive for the virus.
First detected in poultry in the 1990s, H5N2 has also been found in other animals, including pigs, bringing it one step closer to infecting humans.
However, it is not the strain that is causing a ‘pandemic’ in the animal world, as it is H5N1 that has been found everywhere from foxes to raccoons, skunks, cows, seals and deer.
This strain emerged after a version of bird flu that infected wild birds and a version that infected domestic birds met in a cell and swapped genes.
The ease with which it jumped between animals has alarmed officials, who fear it increases the risk it evolves to better infect humans.
Last week, experts raised concerns after the third American to test positive for H5N1 was found to have respiratory symptoms such as coughing.
This raised concerns about the virus spreading to the lungs in patients, risking it spreading more easily to others. It was also different from the other two cases, where symptoms were only seen in the eye.
Viruses bind to receptors – small proteins on the outside of cells – to enter cells and cause an infection.
The human eye has the same receptors as a bird’s lungs, experts say, increasing the risk of infection — but human lungs have different receptors, meaning the virus would have to evolve to learn how to attach to them and become a can cause infection.
A total of 82 dairy farms have now tested positive for bird flu, with Idaho reporting the highest number.
