We know more than 200 species of viruses that cause diseases in humans and most of them have animal origin. Since the end of the 20th century, at least ten major epidemics or pandemics have been caused by pathogens of this type, such as some coronaviruses, alphaviruses, filoviruses, influenzaviruses, orthopoxviruses and members of the flavivirus family. Henipavirus, bunyavirus, arenavirus and other zoonotic viruses have also caused small, sporadic outbreaks.
The presence of domestic and wild animal reservoirs, as well as insect and arthropod vectors, greatly complicates the transmission dynamics of zoonotic viruses and makes control measures very difficult to implement.
This explains why, globally, there are around one billion cases of disease and millions of deaths each year due to zoonoses. What’s more, around 60% of emerging infectious diseases reported worldwide have animal origin. And of the more than 30 new human pathogens detected in the last three decades, 75% are zoonotic.
Fever and ticks in China
In this context, the continuous emergence and reappearance of tick-borne diseases represents an increasing threat to human health. And precisely for that reason, experts at a sentinel (surveillance) hospital in northeast China undertook active monitoring of febrile patients with recent tick bites.
Specifically, Chinese scientists carried out metatranscriptomic sequencing of serum samples obtained from 252 febrile patients between May and July 2023. The investigations resulted in the discovery of a species of human pathogenic virus: the Xue-Cheng virus (XCV), called provisionally named after the native name of Mudanjiang, the city where it has been discovered.
The new virus, detected in ticks of the species Haemaphysalis concinna and Haemaphysalis japonica, belongs to the genus Orthonairovirus of the family Nairoviridae, and the clinical manifestations it caused in 26 patients varied from acute non-specific febrile illnesses to serious pathologies, which resulted in hospital admission.
The data obtained by the researchers therefore suggest that XCV is a new emerging species of tick-borne Orthonairovirus that can infect humans asymptomatically or producing a febrile to severe illness.
The threat of Haemaphysalis concinna
The Haemaphysalis concinna tick is an important species in the community of ectoparasites of animals and humans. It is distributed in 34 countries throughout the Eurasian continent, predominantly in China, Russia and central Europe. In China alone, Haemaphysalis concinna has been reported to transmit at least 22 different pathogens, including the bacteria Anaplasma phagocytophilum, Ehrlichia chaffeensis, Borrelia garinii, Coxiella burnetii and Rickettsia raoultii, the protozoan Babesia microti and several virus species, posing a threat. significant for human and animal health.
This tick can parasitize more than 100 host species. While adult specimens infest wild and farm animals (cattle, goats and sheep), larvae and nymphs feed on small rodents, birds or reptiles. Humans can be attacked by both nymphs and adults. Recently, new human pathogenic Orthonairoviruses, such as wetland virus (WELV), have been isolated from Haemaphysalis concinna.
A fearsome genre
Currently, there are 51 different viruses assigned to the genus Orthonairovirus. They usually infect certain ticks of the argasid or ixodid families, which transmit them to small vertebrates (birds and mammals). In turn, these serve as sources of infection for ticks. Some Orthonairoviruses are transmitted transovarianly in ticks.
The human Orthonairovirus with the greatest impact on public health is the Crimean-Congo hemorrhagic fever virus (CCHFV), which is transmitted by ticks and is endemic in much of Asia, Africa, and southern and eastern Europe, where it causes viral hemorrhagic fever often severe and frequently fatal.
Other viruses that cause occasional illness in humans are Aigai virus (AIGV), which causes febrile illness and viral hemorrhagic fever; Erve (ERVEV), which causes thunderclap headache, and the Issyk-kul (ISKV), Kasokero (KASV), Soldado (SOLV), Dugbe (DUGV), Sōnglǐng (SGLV), Tamdy, Yezo and tick viruses Tǎchéng 1, causing febrile illness.
From a veterinary point of view, the most relevant Orthonairovirus is Nairobi sheep disease (NSDV). In humans it causes febrile illness and in Africa and India it causes lethal hemorrhagic gastroenteritis in small ruminants.
So far, the fatality rate of the Xue-Cheng virus (XCV) in humans is unknown, but the one that triggers Crimean-Congo hemorrhagic fever can reach up to 40%, so the discovery of the new pathogen must be taken with great caution. The increasing burden of tick-borne Orthonairovirus infections is becoming a global public health concern.
(Article originally published in ‘The Conversation’)
#pathogenic #virus #humans #discovered #China
