“Silent Reservoir”: Scientists Find Hantavirus May Persist in Human Semen for Up to Six Years
In a landmark peer-reviewed study, researchers have discovered that the Andes strain of hantavirus can remain detectable in semen more than 70 months after initial infection—raising urgent questions about potential sexual transmission long after patients have recovered.
GENEVA — In a finding that is reshaping the scientific understanding of viral persistence, researchers have discovered that hantavirus—a pathogen best known for causing a severe and often fatal respiratory illness—may remain in human semen for up to six years after the initial infection .
The discovery, published in the peer-reviewed journal Viruses and conducted at the prestigious Spiez Laboratory in Switzerland, documented the presence of Andes virus genetic material in the semen of a 55-year-old man a full 71 months (approximately six years) after he first fell ill . The case involved a Swiss traveler who developed hantavirus cardiopulmonary syndrome (HCPS) after journeying through South America in 2016 .
“This is the first report of a virus from the Bunyavirales order persisting for almost six years in the semen samples of a patient,” the researchers wrote in their paper . The finding places hantavirus alongside other notorious pathogens—including Ebola and Zika—that are known to “hide” from the immune system within the male reproductive tract .
The Science: What the Study Actually Found
The research team, led by Roland Züst of the Spiez Laboratory—a Swiss government institute tasked with countering nuclear, biological, and chemical threats—tracked a single patient over an extended period .
Key Findings at a Glance
| Parameter | Result |
|---|---|
| Virus Strain | Andes orthohantavirus (ANDV) |
| Patient Age | 55 years |
| Infection Origin | South America (acquired during travel) |
| Time Since Infection | 71 months (2,188 days) |
| Virus Detectable in Blood/Urine/Respiratory Tract | No (cleared after ~172 days) |
| Virus Detectable in Semen | Yes |
| Infectious Virus Isolated | No (limited replication activity detected) |
| Potential for Sexual Transmission | Confirmed as “potential” by authors |
The researchers found that while the man’s blood, urine, and respiratory samples had cleared the virus relatively quickly after his recovery, his semen continued to test positive for viral RNA nearly six years later . Whole-genome sequencing revealed only minimal genetic changes—two single nucleotide variants and a 33-base pair deletion—suggesting “very limited replication activity” rather than active viral production .
Importantly, the researchers were unable to isolate infectious virus from the semen samples, meaning the study does not definitively prove that the man could transmit the disease through sexual contact . However, the authors emphasized that this limitation may be due to the inherent difficulty of culturing hantaviruses, and therefore “cannot be ruled out” .
Why the Testes? Understanding the “Immune-Privileged” Sanctuary
The finding, while startling, follows a well-established biological pattern. The male testes are what scientists describe as an “immune-privileged site” —a part of the body where the immune system’s access is deliberately limited to protect the process of sperm production .
“The testes are known to act as a ‘safe harbour’ for at least 27 infectious diseases, allowing some pathogens to persist even after patients appear fully recovered,” researchers noted . Because sperm cells are essential for reproduction, the body moderates its immune response in the reproductive tract, inadvertently creating a sanctuary where viruses can evade immune clearance .
This same mechanism has been documented in:
- Ebola virus – linked to a 2021 outbreak in Guinea that originated from a survivor of the 2014-2016 West Africa epidemic who spread the virus through sexual contact
- Zika virus – known to persist in semen for months after infection, leading to prolonged transmission risk
- Marburg virus – also detected in reproductive tissues
The Andes Strain: A Unique Concern Among Hantaviruses
Not all hantaviruses are created equal, and this distinction is critical to understanding the public health implications of the study. The Andes virus (ANDV) is the strain found in parts of Chile and Argentina and is unique among hantaviruses for a specific reason: it is the only hantavirus known to be transmitted from person to person .
Most other hantavirus strains—including the Sin Nombre virus found in North America and the Puumala virus in Europe—are transmitted exclusively through contact with infected rodent droppings, urine, or saliva. There is no documented evidence of human-to-human transmission for those strains .
A 2025 study on Andes virus immunity noted that “the main risk of person-to-person transmission is to be a sexual partner of an index case, and deep kissing the main mechanism of infection” . This existing understanding of person-to-person spread—primarily through close household contact—makes the possibility of sexual transmission particularly significant.
“The Andes virus is the only hantavirus for which person-to-person transmission has been documented,” the study authors confirmed . “However, the precise routes of transmission have not been identified.”
What This Means for Public Health: Ebola Protocols as a Precedent
The findings have immediate implications for how health authorities manage male patients recovering from hantavirus infection. Global health analytics firm Airfinity has recommended that male patients receive “extensive safe-sex guidance beyond the [42-day] quarantine” period currently associated with hantavirus monitoring .
Public health experts are looking to existing protocols for Ebola survivors as a potential model. The World Health Organization currently recommends that:
- Semen from male Ebola survivors be tested every three months
- Survivors are not considered free of risk until two consecutive negative test results are obtained
- Survivors abstain from sexual activity or use condoms consistently until cleared
- Proper hygiene measures be followed after any contact with semen
“We have a precedent for this kind of guidance,” one health analyst noted. “The question is whether hantavirus, with its lower documented transmission rate, warrants the same level of precaution” .
The Cruise Ship Connection: Why This Matters Now
The research has taken on renewed urgency following a recent hantavirus outbreak linked to the MV Hondius cruise ship, which has been under international monitoring . The vessel, sailing from Argentina to Cape Verde, experienced cases of hantavirus that resulted in multiple fatalities, drawing global attention to the pathogen .
British authorities are currently monitoring confirmed cases and asymptomatic contacts linked to the vessel. The UK Health Security Agency has stated that it “continues to review emerging scientific evidence and would provide confirmed cases and contacts with updated public health advice where necessary” .
Six people who were on the cruise ship linked to the outbreak have left Arrowe Park Hospital on the Wirral to continue their isolation at home, health officials have confirmed .
Limitations of the Research: What We Still Don’t Know
Despite the striking nature of the finding, the research has significant limitations that must be acknowledged.
Small Sample Size
The study is based on a single patient. As the authors themselves note, “further studies addressing the persistence of ANDV will be needed to confirm this hypothesis” . It remains unclear whether long-term persistence occurs in a larger population of long-term survivors of Andes virus infection.
No Infectious Virus Isolated
The researchers were unable to isolate infectious virus from the semen samples. The detection of viral RNA—genetic material—is not the same as detecting a live, replication-competent virus capable of causing infection. However, the authors note that “hantaviruses are difficult to isolate,” and the absence of successful isolation does not rule out the possibility of infectious virus being present .
No Documented Sexual Transmission
Despite the theoretical potential, no confirmed case of sexual transmission of hantavirus has ever been documented . The study concludes that Andes virus has the “potential for sexual transmission”—not that such transmission has occurred.
The Immune Response: A Silver Lining
Amid the concerning findings, there is also good news. The same study documented that the patient developed a “strong, long-lasting neutralizing antibody response” that persisted for years after infection .
Neutralizing antibodies reached a titer of over 30,000 on day 20 post-infection and stabilized at high levels throughout the observation period . Researchers noted that high neutralizing antibody titers upon hospital admission “have been previously correlated with less severe HCPS,” suggesting that a robust immune response contributes to survival .
Most importantly, “repeated symptomatic infection with hantaviruses have not been observed, suggesting life-long protection” .
Broader Context: 22 Viruses Found in Semen
The hantavirus finding is part of a larger scientific picture. A systematic review of 373 studies, published in The Lancet Microbe in December 2024, revealed the detection of 22 viruses in human semen following acute infection .
Of these 22 viruses, only 9 had evidence of confirmed sexual transmission. The review noted that “the persistence of viruses in semen has far-reaching implications for ongoing disease transmission, embryonic development and fertility, and the development of drugs and vaccines” .
Notably, the review found that for hantavirus causing hemorrhagic fever with renal syndrome (a different clinical presentation from the Andes strain), the virus was detected in parts of the male reproductive tract but not specifically in semen . This underscores the unique nature of the Andes strain finding.
Frequently Asked Questions (FAQs)
Q1: Does this mean hantavirus is sexually transmitted?
A: Not yet confirmed. The study found that the Andes strain of hantavirus has the potential for sexual transmission, as viral RNA was detected in semen six years after infection. However, no confirmed case of sexual transmission has ever been documented, and researchers were unable to isolate infectious virus from the samples. More research is needed to determine whether the virus can actually be transmitted this way .
Q2: Which strain of hantavirus is this about?
A: The study specifically examined the Andes orthohantavirus (ANDV) , the strain found in parts of Chile and Argentina. This is the only hantavirus known to be transmitted from person to person through close contact. Other hantavirus strains (such as those found in North America and Europe) are transmitted exclusively through contact with infected rodents and are not known to spread between humans .
Q3: How common is hantavirus infection?
A: Hantavirus infections are relatively rare but can be severe. The Andes strain causes hantavirus cardiopulmonary syndrome (HCPS), which has a case fatality rate ranging from 25 to 40 percent depending on the outbreak . The virus is primarily transmitted to humans through contact with infected rodent droppings, urine, or saliva.
Q4: What should male hantavirus survivors do to prevent transmission?
A: While no formal guidance has been updated yet, health analysts recommend that male patients receive “extensive safe-sex guidance beyond the 42-day quarantine period.” Public health authorities may eventually adopt protocols similar to those used for Ebola survivors, which include regular semen testing and consistent condom use until two consecutive negative results are obtained .
Q5: Was this a new study? When was it published?
A: The study was originally published in the journal Viruses on November 17, 2023. However, news of the finding has resurfaced in May 2026 following a hantavirus outbreak on a cruise ship, which has drawn renewed public attention to the research .
Q6: Why can viruses hide in the testes?
A: The testes are what scientists call an “immune-privileged site.” The body moderates its immune response in the reproductive tract to protect sperm production, inadvertently creating a sanctuary where viruses can evade immune clearance. This same mechanism has been observed with Ebola and Zika viruses .
Q7: How many viruses have been found in human semen?
A: A systematic review of 373 studies published in The Lancet Microbe in December 2024 identified 22 viruses that have been detected in human semen following acute infection. Only 9 of these had evidence of confirmed sexual transmission .
Q8: If I had hantavirus years ago, should I be concerned?
A: If you are a male who recovered from hantavirus infection—specifically the Andes strain—this finding suggests that viral RNA may persist in your reproductive tract. However, it is important to note that researchers were unable to isolate infectious virus, and no sexual transmission has been documented. For peace of mind and to protect partners, consulting with an infectious disease specialist about testing options would be a reasonable precaution .
This is a developing scientific story. Reflecto News will continue to provide updates as further research confirms or refutes these findings and as public health authorities issue updated guidance for hantavirus survivors.