Bacteria Bartonella henselae and other species are the major reason for Cat scratch disease (CSD). 

How it spreads : Flea bites, fighting or getting in contact with the infected cats, or blood transfusions can develop infections in cats. Humans can also be exposed to this infection through the licking or scratching of the affected animal. 

Who is at risk : Cats younger than one year of age, those living in the shelters, current or previous flea infestation, stray cats, or those that hunt are at a high risk of being exposed to these diseases. This disease can affect anyone, but infants, children less than 15 years of age, particularly people with weak immune systems, are more prone to the CSD. 

Symptoms in pets : It has been estimated that about one-third to half of cats get infected at some point in their life. There are no serious symptoms of this disease because most cats may seem healthy or suffer through mild symptoms, including fever, that lasts for just two to three days. However, in rare cases, the symptoms may include tiredness, red eyes, vomiting, swollen lymph nodes, or lack of appetite.
 
Signs in people : A small, raised, solid bump at the scratch site or lymph node swelling may appear in the people exposed to CSD. These symptoms may appear 1-3 weeks after the scratching or licking of the infected cat. The infection can also cause an eye infection, muscle pain, fever, other symptoms, etc.