USA confirms first human case of bird flu with no known traces in animals: ScienceAlert

Another person has fallen ill with bird flu in the United States, but this time health authorities are not clear how the person became infected with the highly pathogenic avian influenza virus (HPAIV).

The patient has fortunately recovered, but according to the Centers for Disease Control and Prevention (CDC), he is the 14th person to contract bird flu in the United States this year and the first patient with “no known direct contact with animals.”

All previous human cases involved workers who caught the virus from sick animals on poultry or dairy farms. This new case is a mystery that the CDC is desperately trying to solve.

On August 22, an adult patient tested positive for the avian virus at a hospital in Missouri; the hospital had previously only tested positive for the H5N1 strain of the virus in poultry and wild birds.

Initially, the patient tested positive for influenza A, but there was no known human subtype. Further testing revealed that the patient had somehow contracted avian influenza, which is currently spreading among wild and domesticated birds and mammals in the United States, as well as in Europe, South America, Africa, parts of Asia, and Antarctica.

This person has no documented history of contact with animals, but it is possible that he or she may have been exposed to an infected animal without his or her knowledge.

CDC officials are currently sequencing the viral genome of this latest human case to better understand where the pathogen came from and how it may have adapted to infect mammals like us.

The patient in Missouri did not transmit the virus to close contacts, and since there has been no known case of human-to-human transmission, the CDC continues to classify the threat to the public from bird flu as “low.”

“The risk of ongoing transmission or infection in the general population remains low,” confirms the Missouri Department of Health and Senior Services.

However, the fact that this patient ended up in the hospital is a worrying sign. It is currently unknown whether the severe symptoms are due to the virus itself or to underlying medical conditions.

CDC Deputy Director Nirav Shah said The Guardian in an exclusive interview in July that her team is closely monitoring the increasing severity of bird flu in humans, as it could be an indication that the virus is mutating in a way that could pose a public health threat.

“If we were to see signs and symptoms in individuals that had no connection whatsoever to a farm or chicken exposure, that would be extremely concerning,” Shah said at the time.

The latest case in Missouri is the first case of bird flu identified through the state's flu surveillance system, which sends suspected strains of flu for further testing.