Feline leukemia virus (FeLV) is a retrovirus that infects cats. FeLV can be transmitted from infected cats when the transfer of saliva or nasal secretions is involved.
Feline leukemia virus (FeLV) is one of the most common infectious causes of disease of cats globally. Infection with FeLV can cause a variety of clinical signs, impacting a cat's longevity and quality of life.
GUIDELINE for Feline Leukaemia Virus Infection.

Feline leukemia virus (FeLV) is one of the most common and important infectious diseases in cats, affecting between 2-3% of all cats in the United States and Canada. Infection rates are significantly higher (up to 30%) in cats that are ill or otherwise at high risk (see below).
PDF | Practical relevance Feline leukaemia virus (FeLV) is a retrovirus of domestic cats worldwide.Progressively infected cats have a poorer. prognosis than cats with regressive FeLV infec-. tion (Table 1). They are at high risk of succumb

Furthermore, visual representations like the one above help us fully grasp the concept of Feline Leukemia Virus Prognostic Factors In Cats With Thoracic Injuries.
WebMD explains feline leukemia virus (FeLV), including symptoms, risk factors, treatments, and prevention.Feline leukemia virus (FeLV) is second only to trauma as the leading cause of death in cats, killing 85% of persistently infected felines within three years of diagnosis.
Causes of Feline Leukemia Virus (FeLV). FeLV in cats is spread through saliva. It is spread most commonly from those exposed to one another for longer periods of time through mutual grooming, mating, or shared food/water/litter boxes.
Risk factors for feline leukemia virus and feline immunodeficiency virus infections Prevention strategies start with recognition of risk factors associated with FeLV and FIV infections. Avoidance or minimization of risk factors that are amenable to control (eg, lifestyle, vaccination)...