By chance, doctors in France discover a previously unknown virus. They find it in the liver of a patient struggling with hepatitis. Now the origin of the new pathogen and the source of the infection are puzzled.
Doctors from the Necker-Enfants Malades Hospital in Paris have discovered a previously unknown virus with colleagues from veterinary medicine. The pathogen found in a patient’s liver was apparently involved in the woman’s hepatitis. The discovery of the new virus came as a complete surprise to doctors, write the experts in a report by the Institut Pasteur Paris.
As a result, the newly discovered virus can be assigned to the so-called circoviruses. It is a family of small, highly resistant viruses that were first identified in various animal species in 1974. The pathogens had led to respiratory, kidney, skin and reproductive problems in the animals infected with it. Tracking down an animal virus in humans is very rare in Europe. The previously unknown virus was provisionally named with the abbreviation HCirV-1. The case of a first human infection with HCirV-1 was published in the journal “Emerging Infectious Diseases”.
The 61-year-old patient had a heart-lung transplant 17 years previously. Due to the transplantation and the treatment with immunosuppressants and high-dose steroids, which had been prescribed for a rejection crisis, the patient was closely monitored medically. Chronic hepatitis with few symptoms was discovered. The doctors now wanted to know how this hepatitis had come about. They took a liver sample to look for the cause. This was examined in March 2022 in a specialized laboratory – also genetically.
The RNA sequences obtained from the sample were analyzed and compared with those of already known microbes. “The goal is to identify interesting sequences among all the sequences obtained, which is like looking for a needle in a haystack!” explains the virologist and study leader Marc Eloit, according to the Pasteur Institute. After matching thousands of RNA sequences, the research team realized it was a previously unknown species of circovirus. The genes of this virus only matched up to 70 percent with known representatives of the circoviruses. Since the experts found no other viral or bacterial RNA, they conclude that the new virus is also the cause of the patient’s hepatitis.
This assumption was supported by the subsequent examination of blood samples from the patient, which were available because of her special medical history. The scientists examined blood samples taken between 2017 and 2019 and found no genetic material of the newly discovered circovirus in them. In more recent samples, on the other hand, the experts found what they were looking for. The researchers found the highest concentration in a sample from September 2021. The experts were also able to demonstrate the spread of the virus in liver cells. According to the information, two to three percent of the patient’s liver was infected with it. This in turn indicates that the new virus was actually involved in the woman’s hepatitis disease.
However, it remains unclear how the woman became infected. The patient had not traveled long distances. This information is important because wolverines, which belong to the mustelid family and have already been identified as hosts for certain circoviruses, live in northern Eurasia and North America. And the woman’s cats, whose stool had been tested for circoviruses, were also found to be carriers. It is conceivable, however, that the patient became infected with the virus when eating infested meat. Because so-called porcine circoviruses have spread in pig fattening in recent decades. However, the actual source of infection in the affected patient is still unknown, as is whether there is a connection between the infection and treatment with immunosuppressants.
The scientists are now working to identify the origin of the virus. After their discovery, they developed a specific PCR test that is available for the diagnosis of hepatitis of unknown cause. A blood test is in progress.
(This article was first published on Friday, February 03, 2023.)
