Cattle Virus Harmless to People for 61 Years Just Killed First Human

The virus that killed a man in Lyon, France had spent 61 years doing nothing to humans.Shamonda is a livestock virus, a cousin of the Schmallenberg virus that swept European herds in 2011, carried in the bite of a Culicoides midge. Pulled from Nigerian cattle in 1965, it was filed away as a curiosity that gave cows a fever and sapped their milk, now turning up from time to time in herds across Africa and in Japan. Not once did it register in a person.Then, on October 8, a severely immunocompromised man in his 60s died of encephalitis at the Hospices Civils de Lyon, and sequencing of his spinal fluid found Shamonda.British officials on November 2 confirmed the virus in dairy cattle in Powys, Wales, and Shropshire, England — the first detections in Great Britain, after earlier finds in Jersey and Ireland. The man is dead, the herds keep testing positive, and every agency involved concedes nobody knows what the first human case means.One scientist who studies midge-borne livestock viruses says the explanation lies less in the virus than in the man it killed.“It is very likely that Shamonda virus poses no risk at all to healthy people,” the retired professor of epidemiology and vector biology at the University of Liverpool, Matthew Baylis, tells The New York Sun. “It is well established that people who are severely immunocompromised can be infected by viruses that the immune systems of other people can fight off.”Which leaves the question Europe is now trying to answer: was Lyon a freak event, or the first case anyone looked for?Eight Weeks to Fatal EncephalitisThe World Health Organization’s outbreak notice, published November 2, lays out a timeline unsettling in its ordinariness. The patient, a rural man who had not traveled abroad in a year, was hospitalized August 18 for an underlying illness. On September 23 came visual disturbances, confusion and seizures.Doctors ran a broad panel for the usual causes of brain inflammation. Everything came back negative. The answer came October 7 from metagenomic sequencing, which reads every scrap of genetic material in a sample instead of testing for suspects one by one. He died the next morning.The strain was one already circulating in cattle over the Swiss border. Viral loads in his organs were enormous. Writing in Eurosurveillance, the investigators put the fatal encephalitis down to the infection without hedging.What finally caught it, an American infectious disease physician says, was not vigilance but equipment.“Sixty years without a human case is largely because it has been 60 years without the tool,” a senior scholar at the Johns Hopkins Center for Health Security, Amesh Adalja, tells the Sun.France has reached the same end this way three times, he notes — Cristoli in 2020, Umbre in 2021, Shamonda now. None had ever been tied to human illness, and each surfaced in French patients dying of brain swelling.“All orthobunyaviruses, all fatal encephalitis, all in patients with no antibodies, all invisible to targeted testing,” Dr. Adalja says.Two Variants, No VaccineWhat makes the Lyon death more than a medical footnote is the animal outbreak’s speed. Veterinarians in eastern France began investigating herds with fever, diarrhea and collapsing milk in June. By October 22, France’s bulletin listed 14 affected European countries and territories. Counting cattle, sheep and horses, it had reached 53 Frenchdepartments by October 13.Two variants are circulating, EU1 through central Europe and EU2 across the north. Germany has found it in horses, sheep, goats and an alpaca.Dr. Adalja cautions the European virus is not the one that idled in Africa and Japan.“SHAV-EU1 and EU2 are reassortants that emerged this summer into naive herds, which means vastly more infected midges biting vastly more mammals than at any point in that history,” he says.A reassortant is a hybrid: two related viruses infect one animal and swap segments of genetic code, producing something herds have never met and carry no immunity against.Why now is a question Mr. Baylis traces partly to a warming continent.“There is strong evidence that climate change has facilitated the spread and transmission of other Culicoides — biting midge — transmitted viruses in Europe, most notably bluetongue virus, and so climate change may have played a role in Shamonda virus’ emergence as well,” he tells the Sun.‘An Alert,’ Not an EmergencyShamonda is not notifiable under European animal health law, so testing differs country to country, and the true scale cannot be measured. There is no vaccine and no treatment.Mr. Baylis sees no case for changing that.“Given the very low risk of Shamonda virus to people in Europe, in my view there is no need to make Shamonda a notifiable disease at this time,” he observes.Dr. Adalja, however, would move on the human side.“Lab-confirmed human infection should be reportable now and is the only way to learn whether Lyon was one case or the first of several,” he stresses.The European Union is not ready to go that far, and says its rules already cover an event of this kind.“With only one human case identified so far, there is currently no basis for introducing routine indicator-based surveillance,” a senior expert in emerging and vector-borne diseases at the European Center for Disease Prevention and Control, Céline Gossner, tells the Sun, noting that European rules already require any unusual event with public health impact to be reported.France’s ministries called the death an exceptional case with no risk to the public. Ms. Gossner reads no more into it than one patient can carry.“The first human infected with SHAV was already receiving treatment for a serious illness, making them more susceptible to infection and complications than the general population,” she explains, noting that “the detection of this single case alone does not provide evidence of the risk to the general population.”For Dr. Adalja, what one death can and cannot prove is a matter of arithmetic.“It is a numerator with no denominator,” he underscores. “What it establishes is narrow and real: human cells support this virus, and it reaches the brain. What it establishes about healthy people is nothing.”The man had leukemia, a stem cell transplant and no antibodies, and carried the virus for at least three months, whereas cattle clear it in days.“That duration is a fact about the host, not the virus,” Dr. Adalja says. Such patients “are sentinels — they make visible what others clear silently — but they are also the worst possible gauge of severity.”Germany, meanwhile, is testing people for antibodies, and Britain’s Food Standards Agency has found no food safety risk.The British detections came as midge season wound down, which buys the continent a winter. Midges die off in the cold, so the virus must reach spring inside the few that survive, or in animals carrying it until biting resumes.Mr. Baylis, for his part, wants the route of infection settled.“The most important question is whether the human case became infected after being bitten by a biting midge, or are there other routes of transmission?” he continues.Ms. Gossner puts it more simply: whether others have had this virus unnoticed.“The key question is whether this was an exceptional infection in a highly susceptible patient or whether other human infections occur but remain undetected,” she says.Dr. Adalja says the answer sits in blood nobody has tested — dairy workers, veterinarians, their households, donors in the affected departments.“That is the denominator, and nothing can be concluded without it,” he adds. “If the rate in exposed people is near zero, Lyon was a singular event in a uniquely defenseless host. If it is not, we have been missing mild human infection all along.”

Cattle Virus Harmless to People for 61 Years Just Killed First Human

Cattle Virus Harmless to People for 61 Years Just Killed First Human

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