Why a bird flu case in Missouri is worrying experts
It’s more evidence that H5N1 is evolving to infect humans.
By Leana S. Wen
October 8, 2024 at 6:00 a.m. EDT
The drumbeat that bird flu is coming closer to humans is growing ever louder. Health officials must step up their game in tracking and preparing for this virus before it spreads further.
Last month, the Centers for Disease Control and Prevention confirmed a case of the illness, also known as H5N1, in a Missouri resident. This was the 14th human case in the United States in 2024 and the 15th since the current outbreak began.
Unlike previous cases and the two others that have since been reported in California, all of which involved people working closely with infected poultry or dairy cows, the Missouri patient had no known animal exposure. The possibility of ongoing human-to-human transmission has heightened alarm among public health experts, especially as the Northern Hemisphere heads into respiratory virus season.
The CDC said the Missouri patient was hospitalized because of other “significant underlying medical conditions” and had multiple symptoms including chest pain, vomiting, diarrhea and weakness. While in the hospital, an influenza test came back positive, so the patient was given antiviral treatment. The individual recovered and was discharged.
At some point, additional testing revealed that the illness wasn’t run-of-the-mill seasonal flu, but rather avian flu. Although initial reports noted no transmission among close contacts, at least seven people around the patient developed symptoms. One was a household contact. The others were health-care workers who interacted with the patient before flu was diagnosed and masking and other precautions were instituted. One person tested negative for flu, but the test could have been done too late to pick up the virus. The others were not tested when they were symptomatic.
Blood antibody testing is underway to see if these individuals had undiagnosed H5N1. Even if these tests are negative, the Missouri case is troubling for three reasons.
First, it is further evidence that H5N1 is evolving to infect humans. Steven J. Lawrence, an infectious-diseases professor at Washington University School of Medicine, told me that in the 27 years since this virus was identified, more than 900 human cases have involved significant exposure to infected animals. “There has been really no sustained human-to-human transmission at all,” he said. Unlike the seasonal flu, which is spread by viruses that bind easily to receptors in the upper airway, past versions of H5N1 have not attached well to airway receptors in humans and other mammals.
“What we’ve seen over the last few years is an increase in the number of mammalian species infected with H5N1,” Lawrence said. One of them is cattle. The current outbreak among dairy cows has spread to 238 herds in 14 states. This is why most human cases were among people with close contact with infected cows, including a cluster involving nine dairy workers in northeast Ohio.
None of these workers went on to infect others, which is why the Missouri case is so curious. The state is not known to have infected dairy herds, and the patient had no contact with farm animals. The individual also did not present with typical flu-like symptoms, which resulted in the delay before instituting precautions.
These facts pose a concerning question: Could there be undetected human-to-human transmission happening? This prospect is especially worrisome as the weather cools and people start coming down with respiratory illnesses. Without readily available rapid tests, it will be difficult to distinguish avian flu from the hundreds of other respiratory viruses circulating.
A troubling scenario is if a person contracts H5N1 and the seasonal flu at the same time. William Schaffner, a professor of infectious diseases and preventive medicine at Vanderbilt University, said this could result in the viruses sharing genes. The H5N1 virus could gain the ability to more readily infect humans. “That could well be the beginning of a much larger outbreak of H5N1, including the possibility of a pandemic,” he said.
Schaffner also highlighted a third worrisome aspect of the Missouri case: Despite the gravity of the situation, the state had not requested the CDC to send a dedicated team to conduct an epidemiological investigation. The CDC’s experts can “provide an element of rigor, completeness and intensity that sometimes state health departments are unable to provide,” he said.
Moreover, Missouri officials have not provided necessary details about this case to the state’s hospitals. Lawrence, who works for a flagship medical center in St. Louis, told me that the health department has not disclosed to infectious-diseases experts there which hospital treated the case or even where in the state the case occurred. The state health department did not respond to my requests for comment.
“We need transparency on data to be able to help prepare,” Lawrence said. Such data will help experts determine whether human-to-human transmission is indeed underway. If so, health officials must ramp up the availability of testing and develop a coordinated plan to deploy vaccines and treatments.
https://www.washingtonpost.com/opinions/2024/10/08/bird-flu-h5n1-human-case-missouri/?