A new study led by researchers at the University of North Carolina School of Medicine is warning that Lassa fever remains a vastly underrecognized public health threat with consequences that extend beyond West Africa. Published in The Lancet Infectious Diseases, the findings all for urgent improvements in diagnosis, surveillance and treatment to curb preventable deaths and reduce the risk of international spread.
Lassa fever, a severe hemorrhagic illness similar to Ebola and listed by the World Health Organization among the world's top pandemic threats, causes thousands of deaths each year. The disease is endemic in Nigeria, Liberia and Sierra Leone, where it is primarily transmitted through contact with infected rodents, though human-to-human transmission can occur via blood and bodily fluids.
Although concentrated in West Africa, the virus has demonstrated global reach. More than 32 imported cases have been recorded worldwide, including in the United States, with roughly one-third proving fatal, underscoring what researchers describe as its international significance.
The study was led by Dr. William A. Fischer II and Dr. David Wohl of the Institute for Global Health and Infectious Diseases. Fischer, who also serves as director of emerging pathogens at the institute, said the disease continues to exact a heavy toll. “Lassa fever remains a major public health threat in West Africa, with high rates of infection and death, often exceeding 20% in some settings,” he said.
He stressed that many of those deaths are preventable. “Many of these deaths can be prevented with early and increased access to diagnostics, supportive care and potentially initiation of effective therapeutics. Furthermore, with over 30 reported cases of Lassa fever imported into non-endemic countries, one third of which were fatal, the importance of early detection and care extends beyond West Africa,” Fischer added.
One of the central challenges, researchers say, is limited diagnostic capacity. Even in endemic countries, testing remains scarce, leaving many infections undetected. In Liberia, the UNC-Liberia team established real-time PCR testing for the virus at Phebe Hospital in collaboration with local health authorities, strengthening research and diagnostic operations in the region.
Yet Dr. Wohl noted that underdiagnosis is not solely a matter of limited laboratory access. “Before you can order the test, you must have clinical suspicion that Lassa fever is possibly causing your patient's illness. Even though we have known about Lassa fever for decades, we don't fully understand the spectrum of the presentation of this infection,” he said, pointing to overlapping symptoms with other common febrile illnesses.
The Prevalence, Pathogenesis, and Persistence (PREPARE) study was conducted between July 2018 and August 2024 at two hospitals in central Liberia. Researchers enrolled 435 patients aged five and above who were admitted with fever or suspected Lassa fever. All participants underwent plasma RT-PCR testing, and confirmed cases were followed for up to a year to assess viral dynamics, immune responses and clinical outcomes.
Findings revealed that 11% of febrile patients had Lassa fever despite not being clinically suspected. Mortality was associated with higher viral loads and weaker antibody responses, while children aged five to 17 accounted for 43% of confirmed cases. “These findings reveal how easily cases slip through routine clinical screening,” Wohl said. “Our data make it clear that without widening our diagnostic aperture to look beyond routine diagnostic assumptions, a substantial number of Lassa virus infections will be missed.”
Researchers warned that missed diagnoses not only worsen patient outcomes but also heighten the risk of transmission in health care settings. “By detecting Lassa fever early, we can help those infected and also keep this dangerous pathogen from becoming a threat for those near and far,” Fischer said. An accompanying editorial in The Lancet Infectious Diseases called for expanded point-of-care diagnostics, vaccines and therapeutics, emphasizing that early detection and effective treatment will be critical to reducing mortality and preventing future outbreaks.
