Is there such a thing as “cow flu” and do we need to be worried? 

First off, let's be clear. As far as I know, there is no such thing as cow flu. What we have are cows being infected with a strain of bird flu. 

According to Science.org,
‘The H5N1 bird flu strain circulating in U.S. dairy cattle is likely infecting far more farm workers than scientists realized, a new study published today by the U.S. Centers for Disease Control and Prevention (CDC) suggests. Tests of 115 dairy workers exposed to the virus in two states found evidence of a recent H5N1 infection in eight of them—an infection rate of 7%’ 

Currently in the United States, we have 46 cases reported of H5N1 infections in humans 45 of these are linked to infections in poultry and cattle. If there is any good news in this report, it's that this virus cannot be passed from human to human. (So far.) Keeping in mind that these are the reported cases, the probability is high that there are many more infections that have not been reported.  

One of the concerns here is that every time a virus infects a human being, there's potential for a mutation that could help increase the possibility of Infecting humans. The CDC will be increasing its testing of dairy workers across multiple states. But the agency states that there's no evidence that the virus is getting better at spreading between humans and considers “the risk to the general public as low”. 

So, one more time, there is no such thing as cow flu.  

But there certainly is something called H5N1 Bird flu, and it does not seem to be going away anytime soon. 

Many human infections with ‘cow flu’ are going undetected | Science | AAAS
Serologic Evidence of Recent Infection with Highly Pathogenic Avian Influenza A(H5) Virus Among Dairy Workers — Michigan and Colorado, June–August 2024 | MMWR
Dutch Bird Flu Infected 1000 | Science | AAAS