Topic Overview

Some insect and spider bites or stings can cause flu-like symptoms to develop within hours of a bite or sting, or they may also be delayed up to 3 weeks. Flu-like symptoms include:

• Fever.
• Shaking chills.
• Muscle or joint aches.
• Headache.
• Swollen glands.
• A vague feeling of illness (malaise).

Flu-like symptoms may not be caused by a bite or sting, but they may mean a more serious problem. Examples of a more serious problems include:

• A toxic reaction, which occurs when insect or spider venom acts like a poison in the body.
• Serum sickness. Venom from insect stings or spider bites and medicines such as penicillin are common causes of serum sickness.
• Lyme disease, a bacterial disease that can be passed by the bite of a deer tick. Symptoms begin within 3 weeks of a bite and often include an expanding red rash in addition to flu-like symptoms.
• Encephalitis caused by the West Nile virus. West Nile virus is spread to people by infected mosquitoes. Most infections are mild. Symptoms usually appear within 3 to 15 days of the bite.
• Malaria, which is caused by a parasite that infects human liver cells and red blood cells. Malaria is an infectious disease carried by certain mosquitoes. Symptoms in the early stages of malaria can be similar to those of many other illnesses caused by bacterial, viral, or parasitic infections. You may have malaria if you have symptoms of malaria and you have been in an area where malaria is present (such as Central or South America, Africa, or Asia), especially in the past 2 months.