What are the risks associated with blood transfusion?

I was transfused with four pints of blood for five days after an accident. Please what are the risks associated with blood transfusion?
Kelechi U.

Although blood transfusions can be life-saving, they are not without risks. When you are getting a transfusion of any kind, it is very important that you let your nurse know right away if you notice any changes in how you feel, such as itching, shivering, headache, chest or back pain, throat tightness, nausea, dizziness, trouble breathing, or other problems. You should report any changes you notice.
Transfusion reactions
Blood transfusions sometimes cause transfusion reactions. There are several types of reactions and some are worse than others. Some reactions happen as soon as the transfusion is started, while others take several days or even longer to develop.
1.    Allergic reaction; this is the most common reaction. It happens during the transfusion when the body reacts to plasma proteins or other substances in the donated blood.
2.    Febrile reaction; the person gets a sudden fever during or within 24 hours of the transfusion. 
Transfusion-related acute lung injury
Transfusion-related acute lung injury (TRALI) is a rare, but very serious transfusion reaction. It can happen with any type of transfusion, but those that contain more plasma, such as fresh frozen plasma or platelets, seem more likely to cause it. It often starts within one to two hours of starting the transfusion, but can happen anytime up to six hours after a transfusion. The main symptom of TRALI is trouble breathing, which can become life-threatening. If TRALI is suspected during the transfusion, the transfusion should be stopped right away.
Acute immune hemolytic reaction
An acute hemolytic (he-mo-LIT-ik) reaction is the most serious type of transfusion reaction, but it is very rare. It happens when donor and patient blood types do not match. The patient’s antibodies attack the transfused red blood cells, causing them to break open (hemolyze) and release harmful substances into the bloodstream. Patients may have chills, fever, chest and lower back pain, and nausea. A hemolytic reaction can be deadly if the transfusion is not stopped as soon as the reaction starts.
Delayed hemolytic reaction
This type of reaction happens when the body slowly attacks antigens (other than ABO antigens) on the transfused blood cells. The blood cells are broken down days or weeks after the transfusion. There are usually no symptoms, but the transfused red blood cells are destroyed and the patient’s red blood cell count falls.
Graft-versus-host disease
Graft-versus-host disease (GVHD) occurs when a person with a very weak immune system gets white blood cells in a transfused blood product. The white cells in the transfusion attack the tissues of the patient who got the blood. Within a month of the transfusion, the patient may have fever, liver problems, rash, and diarrhea.
Infections
Blood transfusions can transmit infections caused by bacteria, viruses, and parasites. Some examples are;
1. Bacterial contamination; rarely, blood gets contaminated with tiny amounts of skin bacteria during donation. Platelets are the most likely blood component to have this problem. Because platelets must be stored at room temperature, these bacteria can grow quickly. (Other components are refrigerated or frozen.) Patients who get these platelets may develop a serious illness minutes or hours after the transfusion starts.
2. Hepatitis B and C; viruses that attack the liver cause these forms of hepatitis. Hepatitis is the most common disease transmitted by blood transfusions. A 2009 study on hepatitis B in donated blood suggested that the risk is about 1 in every 800,000 units or less. About 1 blood transfusion in 1.6 million may transmit hepatitis C.
3. Human immunodeficiency virus; Human Immunodeficiency Virus (HIV) causes Acquired Immune Deficiency Syndrome (AIDS). With improved testing for HIV, the number of transfusion-related AIDS cases continues to drop.