The enigma of the first person infected with bird flu without a known cause is expanding in the United States. The country is investigating seven cases of people who were in contact with the so-called Missouri patient and developed symptoms. Although the authorities rule out that the highly pathogenic avian flu is transmitted between people, the data does not allow it to be ruled out, and scientists’ misgivings are growing due to the poor communication of new cases.
The new information adds even more uncertainty about the impact on humans of the current global H5N1 bird flu crisis, the worst in history. At the threshold of autumn, when a multitude of respiratory viruses begin to emerge, there is the possibility of losing track of what may be the first chain of H5N1 infection in humans. In addition, the arrival of the new seasonal flu season increases the risk that the avian virus will recombine with human variants and generate versions that could cause a pandemic.
The Missouri patient is the first person in the United States to become infected with highly pathogenic H5N1 without being able to explain how. The country is experiencing a major bird flu crisis among dairy cows, with more than 200 farms affected in 14 states. Specific infections have also been recorded among other domestic and wild animals related to these farms, as well as 13 infections in farm workers, all of them mild.
The Missouri patient suffered from previous pathologies. On August 22 he had to be admitted with chest pain, vomiting and diarrhea. A genetic analysis confirmed weeks later that he was infected with a variant of H5N1 very similar to that of cows. But in Missouri there are no known outbreaks on dairy farms, and the patient said he had no contact with livestock farms, pets or wild animals. A relative of the infected person and two health workers also suffered symptoms. Only one of them was tested, and it could not be confirmed if they had H5N1. All of them have now recovered.
Four other health workers who treated the infected patient also had symptoms, but none of them were tested, according to has reported the Center for Disease Control (CDC), the federal authority on epidemics. This central government agency provides support to the states, which are the ones who lead the investigation. Despite the new suspected cases, the Missouri Department of Health assures that there is no evidence that the virus is being transmitted between people, which would represent a qualitative leap in the risk of an epidemic with a potentially pandemic virus. Up to 94 healthcare workers had contact with the infected patient without wearing a mask, the CDC has reported. The agency continues to consider that the risk to human health It’s low.
The pattern of cases in the United States is different from that observed so far. The current bird flu crisis began in 1996 and has since forced the slaughter of 400 million poultry. The highly pathogenic variant 2.3.4.4b has affected mammals, both wild and domestic, causing great mortality, and has spread to almost all continents, including Antarctica. So far, 887 infections in humans and 462 deaths have been detected, a 52% fatality. The vast majority of cases were people who had had close contact with an infected animal, or their family members. Since the new highly pathogenic H5N1 variant emerged in 2022, cases in people registered in the United States have been mild, limited to poultry farms and cellars, and without chains of contagion. The Missouri case is far from the norm and increases suspicions that the virus has gained a feared ability to transmit between people.
The only way to clear up doubts is to do blood tests in search of antibodies against hemagglutinin H5, one of the proteins on the surface of the virus that allows it to bind to human cells and trigger an infection. The CDC is in charge of these analyses. Although the Missouri case was admitted on August 22 and has since been discharged, the CDC has not yet released any serological test results for any of this patient’s close contacts. Missouri now preparing to send blood samples from the latest four suspected cases to CDC labs in Atlanta, reports Reuters.
The slowness and dosage of information is inflaming many experts, who consider it very urgent to clarify the possible chains of contagion. “These cases show the need to take this crisis more seriously,” he explained to the agency. Amesh Adaljainfectious disease specialist at the Johns Hopkins Health and Safety Center. “It is essential to obtain the results of the antibody tests now to evaluate the risk of transmission between humans. This trickle of information from Missouri is unacceptable; “The state should ask for federal help now,” he warned.
The virologist Angela Rasmussenfrom the University of Saskatchewan (Canada), has pointed out in X: “It is important to remember that we still have many cases of covid and other respiratory viruses, this may not be H5N1. The only way to know is to do serological tests, so you have to hurry to do them.” The researcher has just published a nationwide study that has not found H5N1 in milk marketed in Canada, where not a single affected farm has yet been detected. This is another of the enigmas of the current crisis, no one knows why only the United States suffers from it, if the H5N1 avian flu circulates throughout almost the entire planet.
Inmaculada Casas, head of the Respiratory Viruses and Influenza Unit of the National Center for Microbiology, recognizes that “if the results [de los tests serológicos] “If they are positive, it would mean that there is transmission in humans.” Testing blood for antibodies is not as simple as the well-known rapid tests for other infections, he explains. In the case of influenza, a more complex analysis known as hemagglutination with erythrocytes must be performed, which consists of putting the patient’s blood in contact with live H5N1 virus. This test confirms whether the patient has developed antibodies against hemagglutinin H5, characteristic of avian flu. This analysis is not instantaneous, you have to wait 10 or 15 days for the patient to develop antibodies, which may explain why there are still no results.
Elisa Perezveterinary virologist at the CSIC Animal Health Research Center, believes that “it is incomprehensible that there are no results, especially from the first suspected cases registered more than two weeks ago.” The researcher warns that “the lack of transparency can cause the population to lose trust.” “If this were happening in another country, the United States would be complaining,” he adds.
A few days ago, a study of sewage in the state of Texas, one of those affected by H5N1, showed how avian flu went from being undetectable to becoming the most abundant flu virus in the states. 10 cities analyzed starting in March. Although it is not possible to differentiate between human or animal viruses, the absence of outbreaks among people suggests that the origin of all these viruses is dairy farms. A study published last week confirmed that the main route of transmission between animals may be precisely through milk, which concentrates an enormous amount of viruses that are spread through automatic milking systems.
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