Avian Influenza
Loren Bonner
While human infections of the highly pathogenic H5N1 “bird flu” virus remain low, patients may still have questions. What should pharmacists and other frontline health care providers know about the virus at this time?
What are the main characteristics of patients with bird flu?
According to a December 31, 2024, NEJM article describing the characteristics of human A(H5N1) cases identified from March through October 2024 in the United States, authors found that illness was mild and mostly presented as a short period of conjunctivitis in the cases identified during the study period.
More specifically, of the 45 case patients with animal exposures, all had mild H5N1 illness, no one was hospitalized, and no one died. A total of 42 patients (93%) had conjunctivitis, 22 (49%) had fever, and 16 (36%) had respiratory symptoms. Only 15 (33%) had conjunctivitis alone. The median duration of illness among 16 patients with available data was 4 days, according to the research findings.
On January 6, 2025, CDC reported the first human death from H5N1 in the United States. The patient was hospitalized with severe H5N1 illness and passed away. “While tragic, a death from H5N1 bird flu in the United States is not unexpected because of the known potential for infection with these viruses to cause severe illness and death,” said CDC.
As this story went to press, no other deaths have been reported.
What’s the main concern about bird flu mutating?
In the United States, human cases have emerged from exposure to sick dairy cows or H5N1 virus–infected poultry. Currently, human-to-human transmission of the bird flu virus has not been identified in the United States.
While current strains are not known to be transmissible between people, the worry is that a mutation of the virus could change that.
NIH research published December 6, 2024, in Science found that a single modification in the protein found on the surface of the H5N1 virus could allow for easier transmission among humans.
CDC said that since influenza viruses constantly change, CDC routinely sequences influenza to identify genetic changes that could allow for the virus to spread more easily between people or cause serious illness in individuals.
“Sequence analysis and other laboratory tests also allow CDC to assess the susceptibility of the virus to antivirals, accuracy of diagnostic assays, and neutralization of the virus by vaccine-induced antibodies. While adaptations have been detected in the virus from human and animal cases of A(H5N1) during this response, to date, no concerning changes have been identified,” said CDC.
What treatments are available?
Based on observational studies, the antiviral oseltamivir is currently the recommended treatment for H5N1 virus infections in humans.
In the December 2024 NEJM research article, oseltamivir use was high (87%) with most patients receiving treatment within 48 hours after symptom onset. The researchers noted that, to date, with the exception of four viruses with mutations conferring minor decreases in susceptibility to neuraminidase inhibitors and baloxavir, H5N1 viruses from U.S. human infections are susceptible to currently available antiviral agents.
According to a JAMA article published on January 10, 2025, patients with bird flu should be treated with 75 mg oseltamivir twice daily for 5 days. Treatment should be started early, ideally within 48 hours of illness onset, to help prevent severe illness, researchers noted.
Why is it important for health care providers, like pharmacists, to learn more about bird flu?
Providers must be able to 1) recognize the symptoms of bird flu, 2) know to ask their patients about animal or other potential exposures, 3) understand how to test patients for possible infection, 4) know how to treat bird flu in patients, and 5) recognize what to do if they have a patient who may have the virus.
CDC noted that pharmacists in particular can direct patients to their primary care provider and their local and state health department for questions about specific testing and antiviral treatment for H5N1.
What other questions may patients have?
Some patients may want to know how bird flu can be prevented. According to the January 10, 2025, article in JAMA, individuals should avoid direct contact with sick or dead wild or domestic birds or dairy cows, and they should not drink raw milk. Personal protective equipment, such as gloves and masks, is recommended for individuals in contact with sick, dead, and confirmed or potentially infected animals.
Also, seasonal influenza vaccines do not protect against bird flu, although vaccines targeting the virus are in development. ■