Hundreds of Fever Cases in China Linked to Newly Discovered Tick-Borne Virus

Researchers in China, working alongside scientists from the United States, have identified a previously unknown tick-borne virus that may explain a significant number of fever cases that had previously gone undiagnosed.

The virus, named Asian longhorned tick nairovirus (ALTNV), was identified in patients in China who had symptoms consistent with tick-borne infections but tested negative for Dabie bandavirus, the pathogen associated with severe fever with thrombocytopenia syndrome, or SFTS.

The discovery could provide an important explanation for some unexplained illnesses in regions where tick-borne diseases are common. It also highlights the importance of identifying emerging viruses and improving diagnostic testing for people who develop unexplained fever after tick exposure.

The findings were published in The New England Journal of Medicine on Sept. 2, 2026.

A New Virus Emerges From an Unexplained Fever Mystery

The discovery began with patients experiencing fever and other symptoms commonly associated with SFTS.

SFTS is a serious tick-borne disease caused by Dabie bandavirus, or DBV. It can cause high fever, fatigue, gastrointestinal problems and a sharp decline in platelet levels. In severe cases, the illness can become life-threatening.

However, researchers noticed that a considerable proportion of patients with symptoms resembling SFTS were testing negative for DBV.

In some regions, more than 30 percent of patients with these symptoms reportedly had no evidence of the virus normally associated with SFTS. This raised the possibility that another infectious agent was responsible for at least some of the unexplained cases.

Scientists therefore collected samples from patients who had fever and a history of exposure to ticks. Using techniques including RNA sequencing and virus isolation, they identified a previously unknown virus.

Genetic analysis showed that the virus belongs to the Orthonairovirus genus within the Nairoviridae family. Its genetic characteristics were sufficiently different from previously known viruses in the group to support its classification as a distinct virus.

Evidence From More Than 3,000 Patients

To investigate the virus further, researchers examined samples from 3,163 patients who had fever and a history of tick exposure.

Overall, about 10.4 percent of the patients tested positive for ALTNV based on the detection of viral RNA or antibodies indicating previous infection.

The proportion was even higher among people who had already tested negative for DBV. Among those patients, approximately 15.1 percent were positive for ALTNV.

These findings suggest that the newly identified virus could account for some illnesses that previously had no confirmed cause.

However, researchers also found that infection with ALTNV does not necessarily result in severe disease.

Patients infected with ALTNV alone generally experienced a flu-like illness. Fatigue was among the most frequently reported symptoms, affecting approximately 84 percent of patients. Around 80 percent experienced gastrointestinal symptoms.

Laboratory abnormalities were also observed. About 38 percent of patients had low platelet counts, while 36 percent had elevated liver enzymes.

Importantly, the patients in the study who had ALTNV infection alone recovered without reported lasting complications.

Coinfection May Be More Dangerous

One of the more concerning findings involved patients who were infected with both ALTNV and DBV.

Researchers identified 38 patients with coinfections involving both viruses. Seven of those patients died, representing approximately 18.4 percent of the coinfected group.

Patients carrying both viruses also appeared more likely to experience complications than those infected with DBV alone. These included respiratory problems and impaired kidney function.

The results do not necessarily prove that ALTNV itself caused the deaths. Studies involving relatively small numbers of coinfected patients can make it difficult to determine how much each virus contributes to severe illness.

Nevertheless, the findings indicate that coinfection deserves additional investigation, particularly in areas where the two viruses circulate simultaneously.

The Asian Longhorned Tick May Play a Key Role

Researchers also investigated the possible source and transmission route of ALTNV by examining tens of thousands of ticks.

In total, 47,428 ticks from 15 provinces in China were tested. ALTNV genetic material was detected in approximately 1.29 percent of the ticks examined.

The highest detection rate was found in Haemaphysalis longicornis, commonly known as the Asian longhorned tick. Researchers detected the virus in about 1.75 percent of these ticks.

Laboratory experiments provided additional evidence that the species may be capable of transmitting the virus. In experiments involving mice, infected ticks transmitted ALTNV, and the animals developed tissue changes and produced antibodies against the virus.

These findings strengthen the evidence that ticks could play an important role in maintaining and spreading ALTNV.

Further research will be needed to understand exactly how the virus moves between ticks, animals and humans, as well as how widespread it may be outside the areas examined in the study.

Why the Discovery Matters

The identification of ALTNV is significant because tick-borne diseases can be difficult to diagnose when several pathogens produce similar symptoms.

A patient with fever, fatigue, gastrointestinal symptoms and abnormal blood tests may have several possible infections. If standard testing only looks for one known pathogen, another virus could go undetected.

The researchers said the fact that ALTNV and DBV can circulate in the same areas and may share the same tick vector makes accurate diagnosis particularly important.

The discovery could eventually lead to improved diagnostic tests that help doctors distinguish between different tick-borne infections.

It may also encourage additional surveillance of tick populations and patients with unexplained fever, particularly in areas where the Asian longhorned tick is widespread.

What About the United States?

The discovery has also attracted attention because the Asian longhorned tick is an invasive species that has established populations in parts of the United States.

According to the U.S. Department of Agriculture's Animal and Plant Health Inspection Service, the tick has been reported across portions of the eastern United States, with its known range extending from states such as New York and southward toward Georgia, as well as westward into Missouri.

The species is considered a concern because large numbers of these ticks can infest livestock, while ticks in general can carry and transmit pathogens affecting both animals and people.

However, there is an important distinction between the presence of the tick and the presence of ALTNV.

There is currently no evidence presented in the cited information that ALTNV is circulating in U.S. tick populations or causing human infections in the United States.

Therefore, the discovery in China should not be interpreted as evidence of an emerging ALTNV outbreak in America.

Researchers With Chinese and U.S. Affiliations

The study involved scientists from several institutions.

The research was led by scientists associated with Beijing's State Key Laboratory of Pathogen and Biosecurity, which operates under the Academy of Military Medical Sciences in China. Additional researchers were directly affiliated with the Academy of Military Medical Sciences.

The project also included U.S.-based collaborators, including researchers affiliated with the University of Washington and Emory University.

The international collaboration reflects the importance of studying emerging infectious diseases across borders, particularly when pathogens may involve vectors such as ticks that can spread into new geographic areas.

More Research Is Needed

Although the discovery provides compelling evidence that ALTNV is associated with human illness, many questions remain unanswered.

Scientists still need to determine how widely the virus is distributed, how frequently infected ticks transmit it to humans, whether animals serve as reservoirs and how the infection behaves in different populations.

It is also important to determine whether ALTNV infections are occurring elsewhere but are currently being mistaken for other illnesses.

For now, the most practical lesson is that unexplained fever following tick exposure can have multiple possible causes. Continued surveillance, laboratory testing and research will be important for understanding the significance of this newly identified virus.

Sources

• The New England Journal of Medicine, research report on Asian longhorned tick nairovirus, published Sept. 2, 2026.
• University of Minnesota Center for Infectious Disease Research and Policy, report on the discovery and associated clinical findings.
• U.S. Department of Agriculture Animal and Plant Health Inspection Service, information concerning the Asian longhorned tick in the United States.

Disclaimer

This article is provided for informational and educational purposes only. It should not be considered medical advice, a diagnosis or a prediction of disease risk. The discovery of ALTNV in China does not establish that the virus is circulating in the United States or elsewhere. Readers with concerns about tick exposure, unexplained fever or other symptoms should consult a qualified healthcare professional.