Feline leukemia virus is a retrovirus that infects cats. FeLV can be transmitted from infected cats when the transfer of saliva or nasal secretions is involved.
How do cats act when they have feline leukemia can vary widely. While some cats may remain asymptomatic for extended periods, others develop noticeable behavioral and physical changes.
Feline leukemia virus is spread through the saliva of the infected cat by sharing food or water dishes or when cats groom, play with, or bite each other. Since the signs and symptoms of FeLV can be like other medical conditions, the best way to diagnose it is to see your veterinarian immediately.
The risk increases if they spend any time outside or with other cats who have not tested negative (even cats that hang out in screened in rooms or catios may have saliva contacts with other cats).

Furthermore, visual representations like the one above help us fully grasp the concept of Male Cat Leukemia Risky Behaviors.
Discover how cats act with leukemia, including symptoms, risks, and care tips for FeLV-infected felines. Learn how to manage and prevent this virus.
Discover how feline leukemia in cats spreads, its symptoms, and how to protect your cat through testing, vaccination, and early care.
In summary, leukemia is a serious condition that can affect cats, leading to a range of symptoms such as lethargy, weight loss, and swollen lymph nodes. As a pet owner, it is important to be aware of the signs of leukemia in cats and seek veterinary care if you suspect that your cat may be affected.

Such cats include cats living with infected cats or with cats of unknown infection status, cats allowed outdoors unsupervised where they may be bitten by an infected cat, and kittens born to infected mothers.
ABCD cats & vets: GUIDELINE for Feline Leukaemia Virus Infection.