I don't think overwork will lead to fever. It's good to overwork a little bit but not too much if you want to see progress. You get stronger faster when you add more and more weight - you don't gain muscle by using the same 30 Kg barbell everyday.
Have good sleep, have a contrast shower(alternating hot and cold water for a few minutes or keep on doing exercise that is not so intense.
Good sleep help to heal your muscle and let them grow, contrast shower and exercise improves blood circulation thus heals your soreness too!
Correct me if I'm wrong...

Too Much Exercise May Decrease Immunity
However, there is also evidence that too much intense exercise can reduce immunity. This research is showing that more than 90 minutes of high-intensity endurance exercise can make athletes susceptible to illness for up to 72 hours after the exercise session. This is important information for those who compete in longer events such as marathons or triathlons.

Intense exercise seems to cause a temporary decrease in immune system function. Research has found that during intense physical exertion, the body produces certain hormones that temporarily lower immunity.

Cortisol and adrenaline, known as the stress hormones, raise blood pressure and cholesterol levels and suppress the immune system. This effect has been linked to the increased susceptibility to infection in endurance athletes after extreme exercise (such as marathon running or Ironman-distance triathlon training).

If you are training for ultra-endurance events, a key component of your training should be including enough rest and recovery days to allow your body (immune system) to recover. If you are feeling run-down or have other symptoms of overtraining syndrome --such as increased resting heart rate, slower recovery heart rate, irritability or general heaviness and fatigue -- you may need to tone down your workouts as well.

If you are already ill, you should be careful about exercising too intensely. Your immune system is already taxed by fighting your infection, and additional stress could undermine your recovery. In general, if you have mild cold symptoms and no fever, light or moderate exercise may help you feel a bit better and actually boost your immune system. Intense exercise will only make things worse and likely extend your illness.