Scientists in China have identified a previously unknown tick-borne virus during an extensive investigation into patients who developed fever and other unexplained symptoms after being bitten by ticks. The pathogen, known as Asian longhorned tick nairovirus (ALTNV), was detected in more than 10% of the 3,163 symptomatic patients included in the study.
ALTNV infection was associated with fatigue, gastrointestinal problems, reduced platelet counts, and elevated enzyme levels, which may indicate liver or tissue injury. The discovery is especially significant because it offers a possible explanation for patients whose illnesses resembled severe fever with thrombocytopenia syndrome but whose tests were negative for the virus normally associated with that condition.
Researchers also found ALTNV in ticks collected from several Chinese provinces and demonstrated its transmission to mice under laboratory conditions. Although patients infected with ALTNV alone recovered, a group carrying both ALTNV and Dabie bandavirus experienced more respiratory complications, kidney impairment, and several deaths.
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Unexplained Fever Cases Led to the Discovery
Chinese researchers had been monitoring patients in regions where tick-borne diseases regularly occur. Part of the investigation focused on severe fever with thrombocytopenia syndrome, commonly known as SFTS, which emerged in China in 2009 and has since been documented in several Asian countries.
SFTS is typically caused by the Dabie bandavirus (DBV). The infection can produce high fever, vomiting, diarrhea, reduced platelet and white blood cell counts, neurological complications, bleeding, and multiple-organ failure, with reported fatality rates ranging from approximately 10% to 30%.
However, about 30% of patients with symptoms resembling DBV infection tested negative for the known pathogen. Scientists therefore examined their blood samples for genetic traces of other viruses, eventually isolating ALTNV as a separate member of the orthonairovirus group.
More Than 300 Patients Showed Evidence of ALTNV
The researchers studied 3,163 patients treated at sentinel hospitals after experiencing tick exposure and febrile illness. ALTNV RNA or virus-specific immunoglobulin M antibodies were found in 10.4% of participants, which is about 329 people.
Among patients who tested negative for Dabie bandavirus, 15.1% showed evidence of ALTNV infection. The findings were published in the New England Journal of Medicine report on the newly identified orthonairovirus on September 2, 2026.
The reported percentage should not be interpreted as the infection rate among the general population or everyone bitten by a tick. Participants were symptomatic patients receiving treatment in areas where tick-borne pathogens were already known to circulate.
Symptoms Could Easily Be Mistaken for Flu
ALTNV infection frequently produced symptoms resembling influenza or another common viral illness. Patients experienced fever, tiredness, muscle discomfort, and digestive problems, making the infection difficult to identify without specialised laboratory testing.
Among patients infected only with ALTNV, 84% reported fatigue, and 80% experienced gastrointestinal symptoms. Thrombocytopenia, the medical term for a reduced platelet count, was found in 38% of these patients.
Platelets help the blood clot, so extremely low levels can increase the possibility of bruising or bleeding. However, researchers did not find a link between ALTNV infection alone and severe bleeding among the patients examined.
Elevated aminotransferase concentrations were detected in 36% of the ALTNV-only group. These enzymes may rise when the liver or other tissues are inflamed or injured, although all patients infected only with ALTNV eventually recovered completely.
Coinfections Were Associated With Worse Outcomes
The clinical findings became more serious when ALTNV occurred alongside Dabie bandavirus. Researchers identified 38 patients who had simultaneous infections with the two tick-borne viruses.
Respiratory symptoms affected 61% of coinfected patients, compared with 38% of those who had DBV alone. Kidney impairment was recorded in 84% of the coinfection group, compared with 66% among patients infected only with DBV.
Seven of the 38 coinfected patients died, producing a mortality rate of 18.4% in that group. The deaths cannot be attributed solely to ALTNV because every fatal case also involved DBV, a virus already capable of causing life-threatening disease.
Additional studies will be required to determine whether ALTNV directly intensifies DBV infection. Researchers must also examine whether age, underlying medical conditions, or delays in treatment influenced the outcomes.
Virus Detected in Ticks Across 15 Provinces
Scientists screened 47,428 ticks collected from 15 Chinese provinces to investigate how widely the virus was circulating. ALTNV genetic material was detected in 1.3% of all ticks examined, indicating that the pathogen was not limited to patient samples.
The highest detection rate, 1.8%, occurred in Haemaphysalis longicornis, commonly called the Asian longhorned tick. Laboratory experiments demonstrated that this tick could transmit ALTNV to mice, strengthening the evidence that it serves as a vector.
Researchers classified ALTNV within the family Nairoviridae after genetic and laboratory analysis. Its proteins shared less than 80% amino-acid identity with those of previously recognized species in the same genus, supporting its classification as a distinct virus.
Asian Longhorned Tick Is Present in the US
The Asian longhorned tick is native to eastern China, Japan, Korea, and parts of the Russian Far East. It has also spread to Australia, New Zealand, the Pacific islands, and portions of the United States.
According to the US Department of Agriculture’s official Asian longhorned tick information, American officials reported the species in New Jersey in 2017. It has since been collected in multiple areas across the eastern half of the country, from New York south to Georgia and west to Missouri.
The tick’s presence in America does not mean ALTNV is also circulating there. The new investigation documented the virus in China and did not report infections among US patients or ticks.
Discovery May Improve Clinical Diagnosis
Many tick-borne infections initially cause similar problems, including fever, weakness, headache, muscle pain, and gastrointestinal illness. These overlapping symptoms can make it difficult for doctors to identify the responsible pathogen based on a physical examination alone.
ALTNV now provides another possible explanation when patients become ill after tick exposure but test negative for established infections. Improved diagnostic testing may help clinicians distinguish ALTNV from DBV, influenza, and bacterial diseases, each of which requires different treatment approaches.
No specific vaccine or approved antiviral therapy currently exists for ALTNV. Medical care is therefore supportive and may involve hydration, fever control, and monitoring of platelet counts, liver function, breathing, and kidney health.
Surveillance and Prevention Remain Essential
Important questions remain about ALTNV’s incubation period, animal reservoirs, geographical distribution, and ability to cause mild or symptom-free infections. The original study focused on people seeking hospital care, which likely meant it missed less severe cases.
The CDC’s guidance on preventing tick bites recommends wearing protective clothing, using registered repellents, and checking the body after visiting wooded, grassy, or brush-covered locations. Attached ticks should be removed promptly with fine-tipped tweezers, while anyone who develops a fever, a rash, or an unexplained illness after a bite should seek medical care.
The discovery does not indicate an immediate global health emergency, but it highlights the value of investigating unexplained illnesses beyond familiar pathogens. Continued surveillance will be necessary to determine where ALTNV circulates, how frequently it infects people, and whether particular patients face a greater risk of severe complications.
