A person in Missouri has been diagnosed with bird flu, despite no apparent contact with infected animals, according to a CDC announcement made on Friday evening.

The absence of animal contact raises alarm over the potential for the virus to transmit between humans. While the CDC currently rates this risk as “low,” health officials are vigilant.

This individual marks the 14th case of H5N1 bird flu in the U.S. this year and is the first to be hospitalized without identifiable contact with an infected animal. Previous cases involved people who had mild symptoms after working on farms with H5N1 outbreaks.

Details on how this Missouri resident contracted the virus remain unclear, and their level of illness is unknown. The unidentified patient was hospitalized on August 22 and received antiviral treatment after testing positive for the flu. Subsequent tests indicated it was H5N1, leading to their confirmation on Thursday. The patient has now been discharged and is recovering.

Health experts are worried about bird flu because it has been fatal in about half of the recorded cases worldwide. Many milder instances may have gone unreported.

Investigating the Source

The CDC plans to study the genetic makeup of the strain from this patient to determine if it’s linked to those in other affected individuals or animals.

Understanding the virus’s origin is essential for assessing its potential risk to the public, according to Dr. Jesse Goodman, a Georgetown University medicine professor and former chief scientist at the FDA.

If the infected individual has the same strain as previous cases, a transmission chain must exist—either from sick animals or from another infected person, Goodman stated.

Lisa Cox, spokesperson for Missouri’s health department, shared that the patient’s contacts remained symptom-free during the observation phase, indicating no further spread of the virus.

There’s a possibility that this individual has a new strain of the virus that hasn’t been previously identified. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, suggests the Missouri patient likely contracted a different strain after coming into contact with an infected migratory bird.

With many birds migrating during late summer, Osterholm noted that this season sees increased movement of the virus. He mentioned that a backyard bird feeder could be a typical exposure route, though he didn’t confirm if the patient had one, emphasizing that this kind of contact is not unusual.

Mitigating the Risk

The ongoing outbreak in the U.S. is believed to have originated from a wild bird that infected cattle on a Texas dairy farm, leading to further spread across over a dozen states, although no similar cases have been reported in Missouri so far. Strains of H5N1 have been known to circulate in wild birds since at least 1997.

Humans have not displayed high vulnerability to the H5N1 virus, as noted by Dr. Paul Offit, a pediatric infectious disease expert and director of the Vaccine Education Center at Children’s Hospital of Philadelphia. So far, only individuals exposed to significant amounts of the virus on farms have shown symptoms, which could penetrate deep into the respiratory system. He suggested that the Missouri patient, described by state officials as having an “underlying medical condition,” may have had increased susceptibility.

Even individuals vaccinated against seasonal flu lack immunity to H5 flu viruses, which could lead to serious illness upon infection, Offit added.

The CDC monitors flu activity closely, particularly in areas with known animal outbreaks. Currently, there are no indications of unusual flu activity in the general population, according to their report.

Goodman has commended the CDC’s efforts in monitoring, but believes that the agency and others should do more to proactively prevent any significant outbreaks. “This is yet another warning signal,” Goodman remarked. Earlier this week, he co-authored an opinion editorial in the Journal of the American Medical Association, advocating for increased funding in public health, including a vaccine strategy to combat H5N1 both domestically and internationally.

“We must prepare for potential infectious disease outbreaks before they happen; it’s too late when they do,” he cautioned. “Hopefully, this won’t escalate into a public health issue, and I believe that’s the most likely outcome, but we need to be vigilant. We can’t act as if we will never experience another pandemic.”

The CDC has indicated that it assesses the general public’s risk from H5N1 as “low” and is not currently altering its guidelines regarding the virus.

According to Offit, there hasn’t been enough information released about the patient in Missouri to gauge how serious the situation is.

“We are waiting for crucial information, as always,” Offit expressed. “You have just enough details to feel anxious but not enough to determine if the anxiety is warranted.”