The timeline is far easier to keep track of if you were infected from, and found on you, a tick. Otherwise, people usually wait for symptoms to appear and that can take weeks. Most people don't actually get a lot of the symptoms that are "advertised" until later, such as rashes, bullseye rash, pain and fatigue. A lot of the symptoms are a lot like flu, such as:
- Lack of energy
- Headache and stiff neck
- Fever and chills
- Muscle and joint pain
- Swollen lymph nodes
In many cases, none of these symptoms are noticed, so the virus festers and grows unknown to the patient infected. Once it continues and the diagnosis is prolonged, and without any immediate attention by a physician the person enters the latter stages of infection. This stage is the most serious, called Late persistent Lyme disease.
Once in this stage, usually 1-4 months after infection, the person can suffer a myriad of dangerous symptoms. This can also affect someone if they were misdiagnosed or ineffectively treated. Damage to joints, nerves, the brain, things like arthritis can occur months and years later.
I believe it's for these reason that people are so fearful of Lyme if it does go wrongly or misdiagnosed.