Latest human H5N1 bird flu case in US is 1st to cause respiratory symptoms

A third human case of bird flu has been linked to the ongoing outbreak in cows on U.S. dairy farms — and this one came with respiratory symptoms, such as cough, the Centers for Disease Control and Prevention (CDC) reported May 30.

Officials first became aware of bird flu spreading among U.S. dairy cows in March, and since then, the viral disease has been detected among cattle on farms in nine states. The type of bird flu spreading is known as H5N1, which has sporadically infected individual humans in the past but has never spread widely from person to person. However, these rare human infections can sometimes be fatal, and there's concern about the virus picking up the necessary mutations to spread easily through the populace.

Prior to the outbreak in cows, only one person in the U.S. had ever been infected with H5N1, as far as we know. Now, since the outbreak began, three people have likely been infected via exposure to sick cows. The first person infected by a cow was in Texas, and the second was in Michigan; both are dairy-farm workers and developed only eye infections from the virus before recovering.

The third, newly reported case linked to cow exposure was also in Michigan but on a different farm. The person was given treatment and is now isolating at home as their symptoms resolve. This infection is notable because it is the first human H5N1 case in the U.S. associated with respiratory symptoms. 

Related: H5N1: What to know about the bird flu cases in cows, goats and people 

"This is the first human case of H5 in the United States to report more typical symptoms of acute respiratory illness associated with iNFLuenza virus infection, including A(H5N1) viruses," the CDC reported. "The patient reported upper respiratory tract symptoms, including cough without fever, and eye discomfort with watery discharge." 

In humans, bird flu viruses, including H5N1, can cause both mild symptoms — including pink eye, cough, sore throat, runny nose and body aches — as well as severe ones, such as pneumonia, difficulty breathing and seizures. If severe, the infections can be fatal, but antiviral drugs available for seasonal flu can help treat the disease.