Those Highly Pathogenic Avian Influenza Viruses known as A(H5N1) that have led to the destruction of millions upon millions of birds around the world have, according to the Centers for Disease Control and Prevention (CDC), also caused 19 human illnesses in eight countries.

Nine of these sporadic human cases were severe, and five resulted in death.  Three human illnesses were mild, and seven resulted in only asymptomatic cases. Only one of those cases involved a resident of the United States, which occurred in April 2022. 

“The individual reported fatigue without other symptoms, and a low level of A(H5N1) viral RNA was detected in a single upper respiratory tract specimen, CDC reports. “It is possible that detection of A(H5N1) viral RNA resulted from deposition of non-infectious viral material in the upper respiratory tract of the individual and did not represent true infection, similar to the environmental contamination that was attributed to the two asymptomatic cases in poultry workers reported in Spain.”

According to the CDC report on human bird flu cases, from January 2022 through Dec 27, 2023, “nearly all cases reported since January 2022 had recent exposure to sick or dead poultry, and no cases of human-to-human HPAI A(H5N1) virus transmission were identified. Nine cases (four children, five adults) had severe disease, and five died.”

The geographic breakdown for the human cases outside of the United States includes:

• Cambodia – Six cases, two in February 2023, two in October 2023, and two in November 2023. Four deaths. Two mild illnesses.
• Chili – One critical illness in March 2023.
• China – Two illnesses in September 2022 and January 2023.  One died, and one was hospitalized without reporting the outcome.
• Ecuador – One critical illness survived in December 2022.
• Spain – Two cases, in September and October, both Asymptomatic.
• United Kingdom- Five cases, all Asymptomatic in January 2022, May 2023, and July 2023
• Vietnam – One case In October 2022, critical illness survived.

The CDC puts the human illness data in context by reporting: “While HPAI A(H5N1) viruses are currently circulating widely in wild birds and poultry in many geographic regions, relatively few human cases of A(H5N1) have been reported in recent years.”

Going back before the current incidents, CDC reports that since 1997, a total of 902 sporadic human A(H5N1) cases have been reported from 22 countries, caused by different HPAI A(H5N1) virus clades [23,24], with a cumulative case fatality proportion of greater than 50 percent. Human A(H5N1) cases peaked in 2006 (115 cases, nine countries) and 2015 (145 cases, four countries) primarily because of a large epidemic in Egypt with 136 cases 

“Nearly all reported human A(H5N1) cases had poultry exposures, such as to sick or dead poultry or visiting live poultry markets, the CDC reports. “Rare, limited, and non-sustained instances of human-to-human HPAI A(H5N1) virus transmission likely occurred in a small number of family members following prolonged, close unprotected exposure with a symptomatic case-patient during 2004-2007 in multiple countries.

The CDC finds bird flu viruses have become widespread, causing record outbreaks in wild, backyard, village, and commercial farm birds. Over 11,400 bird outbreaks of HPAI A(H5N1) viruses were reported by 84 nations.  In the U.S. alone, avian flu has taken the lives of at least 77.8 million birds with no end in sight

Finally, the CDC notes that sporadic reports are occurring of mammals being infected by the HPAI viruses. The latest such report involves a Polar Bear. The viruses occasionally infect mammals that eat (presumably infected) birds or poultry and mammals exposed to environments with high virus concentrations.