Review of gammaretroviruses in humans: what it says about FeLV infection statuses in cats
Pathogens (Basel, Switzerland) · 2026
In plain language
This is a literature review, not a new study. Its main question is about humans, not cats. It describes four ways FeLV infection can present in cats, depending on how effective the immune response is. It also notes that in some of them the virus's DNA can be hard to detect. A single negative test does not on its own show that the virus is gone.
Scientific detail
This is a 2026 review in Pathogens on gammaretrovirus infections in humans, available as open-access full text. It covers multiple species and reports no sample size. Its central question is potential human exposure to animal gammaretroviruses; it provides no new experimental evidence on feline disease and does not establish human FeLV infection.
The review recognizes four FeLV infection statuses in cats: progressive, regressive, focal, and abortive, depending on the effectiveness of the immune response. This is a synthesis of cited literature. The passage assessed does not give the design, sample size, or controls of the underlying studies, so it is graded as level C evidence rather than controlled experimental evidence.
Regarding detection, the review states that viral DNA can be challenging to detect in focal and abortive infections because it may be only locally present or no longer detectable. This describes a limitation of viral DNA detection; it does not establish that an individual negative test proves eradication.
The authors also note broader limitations: prior contamination problems and endogenous retroviruses discouraged further human testing; diagnostic assays may be hindered by low DNA or antibody levels, suboptimal replication, rapid immune control, or absent antibodies following early-life infection; and the absence of germline viral sequences does not prove absence of historical infection. Large population surveys for novel retroviruses have not been performed.
What we know
The review describes four FeLV infection statuses in cats (progressive, regressive, focal, abortive), depending on the effectiveness of the immune response, and states that viral DNA can be hard to detect in focal and abortive infections. This comes from cited literature and is graded level C; the passage assessed does not detail the underlying studies.
What we don't know
This review does not establish human FeLV infection or provide new data on disease outcomes in cats. The design and sample size of the studies behind the infection categories are not known from the passage. Large population surveys for novel retroviruses have not been done, and a negative test does not by itself show the virus has been cleared.
Evidence
EvidenceLevel C — Preliminary evidenceConfidence 100/100
The review recognizes four FeLV infection statuses in cats: progressive, regressive, focal, and abortive, depending on the effectiveness of the immune response.
Excerpt verified in the source — verbatim, in the source's own language“In cats, four types of FeLV infection status are recognized, depending on the effectiveness of the immune response, namely, progressively infected, regressively infected, focally infected, and abortively infected [ 257 ].”
This is a direct feline statement summarized from cited literature. The supplied passage does not provide the underlying study design, sample size, or controls, so it does not support classification as controlled experimental evidence.
EvidenceLevel C — Preliminary evidenceConfidence 100/100
The review states that detecting viral DNA can be challenging in focal and abortive FeLV infections because viral DNA may be locally present or no longer detectable.
Excerpt verified in the source — verbatim, in the source's own language“For the latter two types, which are more common than progressive infection, detecting viral DNA can be challenging, as viral DNA is only locally present or is no longer detectable, indicative of virus eradication [ 257 ].”
The preceding sentence identifies the latter two types as focal and abortive infection. This passage describes a limitation of viral DNA detection; it does not establish that an individual negative test proves eradication.
Provenance
Source: Gammaretrovirus Infections in Humans in the Past, Present, and Future: Have We Defeated the Pathogen?
AVA