Infection

Cancer and cancer treatment can weaken a person's immune system. The immune system is the body's natural defence against infection and disease. An infection occurs when harmful organisms (such as bacteria or viruses) enter the body and cause illness because the immune system is not able to destroy them. White blood cells (WBCs) are an important part of the immune system. The body's other natural defence systems, such as the skin – the first and most important physical barrier – also help protect a person against infections.

Infections can be very serious in people who have cancer or are receiving cancer treatment. It is important to prevent infections and treat them early if they occur.

Causes

Cancer and certain types of cancer treatment can increase the risk of infection.

• Some cancers, such as leukemia, multiple myeloma and lymphoma, start in the immune system cells and can affect the bone marrow. They can prevent it from making enough healthy WBCs.
• Cancers that spread (metastasize) to the bone and bone marrow, such as breast and prostate cancer, can lower the level of red blood cells, white blood cells and platelets in the blood.
• Surgery and invasive procedures (such as putting in an intravenous line) cause a break in the skin or mucous membrane, which can allow organisms to enter the body.
• Removing the spleen (splenectomy) for certain types of cancer may lower a person's resistance to infection because the spleen is an important part of the immune system.
• Corticosteroids may be used as part of cancer treatment or to help reduce pain and swelling associated with cancer. Corticosteroids can suppress the immune system. They may also hide the signs and symptoms of an infection.
• People with poor nutrition because of their cancer or its treatment can have a weakened immune system.
• Urinary catheters or feeding tubes can provide a way for harmful organisms to get into the body.
• Indwelling central lines that are used for giving chemotherapy, blood products, intravenous fluids and medications, can also provide a way for harmful organisms to get into the body.

WBCs play a key part in defending the body against bacteria and viruses, which can cause infection. Neutrophils are a type of WBC that surround and destroy bacteria, and they are very important in fighting infection. When WBCs are lowered, especially neutrophils (called neutropenia), because of cancer treatment, a person has a higher risk of getting an infection. The risk of infection is related to the length and severity of neutropenia. The lower the neutrophil count and the longer the level remains low, the higher the risk of infection.

Some cancer treatments are more likely than others to lower the WBC count.

• Chemotherapy can cause bone marrow suppression, which can lower the WBC count. Some chemotherapy drugs have a greater effect on the bone marrow and immune system than others.
• Radiation therapy can affect the bone marrow and lower WBC counts. This is especially true if an area that contains a large amount of bone marrow (such as the pelvic bones) or a large part of the skeleton is irradiated (such as total body irradiation). This is also more likely to happen if the person is receiving chemotherapy at the same time as radiation therapy.
• A stem cell transplant uses high-dose chemotherapy, radiation therapy or both to kill cancer cells and destroy the bone marrow cells to make room for new stem cells. A person who receives a stem cell transplant will have a low WBC count for a while before new blood cells start to grow. People who receive an allogeneic stem cell transplant can develop a condition called graft-versus-host disease (GVHD). They may be given drugs that suppress the immune system to prevent and treat GVHD. These drugs also increase the risk of developing infections.

Back to top

Sites of infection

Infections can occur almost anywhere in the body. However, the most common places for an infection are the:

• skin and mucous membranes
• respiratory system (such as the sinuses or lungs)
• blood
• urinary system (such as the bladder or kidneys)
• gastrointestinal tract (such as the mouth, stomach or intestines)
• nervous system (brain or spinal cord)

Back to top

Signs and symptoms

Any of these signs and symptoms may signal an infection:

• fever (temperature over 38^oC)
  • This is the most common sign of infection.
  • A person can also have an infection and not have a fever.
• chills or shivering
• unusual sweating
• mouth sores
• redness, heat, swelling or discomfort from a wound, incision or area around an intravenous line or vascular access device site
• sore throat
• cough, which may produce phlegm
• shortness of breath
• frequent, painful urination
• diarrhea
• abdominal pain
• unusual vaginal discharge or itching
• headache or stiff neck

Back to top

Types of infection

An infection can be caused by many types of micro-organisms, such as bacteria, viruses, fungi or protozoa. Infections in people with cancer are often caused by micro-organisms that normally live on their skin, in their mouth or in their intestines. These organisms do not usually cause a problem in people with a normal immune system. But in someone with cancer whose immune system is not working as well, these organisms are given the opportunity to multiply. These are called opportunistic infections, and they can be serious.

Some common causes of infection are discussed below.

Bacterial infections

Bacteria are the most common type of infection-causing organism in people with cancer. Bacteria can cause serious infections in a person with a low WBC count. There are many bacteria that live on and in our bodies (called normal flora), which do not usually cause infection, but they may cause problems in a person whose blood cell counts are low and immune system is weak. There are many different bacteria that cause infection, some of which include:

• Clostridium difficile (C. difficile) – can cause an intestinal infection and diarrhea in people taking antibiotics
• Enterococci – normally found in the stomach and intestines of healthy people; can be serious in people with vancomycin-resistant enterococci (VRE) because the bacteria have become resistant to the antibiotic typically used to treat the infection
• Escherichia coli (E. coli) – can affect the intestines and cause fever and diarrhea
• Pseudomonas – rarely cause infections in people with healthy immune systems; can be serious in people with a weakened immune system
• Staphylococcus aureus (S. aureus) – mainly affects the skin; can be serious in people with methicillin-resistant Staphylococcus aureus (MRSA) because the bacteria have become resistant to the antibiotic typically used to treat the infection
• Streptococcus – common bacteria that can cause tonsillitis; can cause pneumonia or inflammation of the sac around the heart (pericarditis) in people with weakened immune systems

Viral infections

Viruses cause infections such as the common cold. Certain viruses can cause serious infections in people with very low WBC counts. Most viral infections in people with cancer are caused by:

• varicella zoster virus
  • The varicella zoster virus (VZV) causes chicken pox and shingles. After a person recovers from the infection, the virus remains dormant (inactive) in certain nerve cells of the body. If the immune system becomes stressed, as can occur with cancer treatments, the person could have an outbreak of shingles.
  • Shingles usually occurs as patches of red or blistered spots that look like chicken pox along a line of skin, most often on the back or chest. Shingles often occurs on one side of the body only – it does not cross the midline. Shingles can be very painful, with a deep burning feeling along the nerves injured by the infection. The pain will often start before the spots occur. There can also be fever, chills and flu-like symptoms as the spots develop.
  • The virus can spread to other organs such as the lungs or brain, which can be very serious.
• herpes simplex virus
  • The herpes simplex virus (HSV) causes cold sores and genital herpes. This virus can remain dormant in the body, and when the immune system is suppressed, it can flare up and cause a severe case of cold sores.
  • HSV can also cause pneumonia and inflammation of the brain called encephalitis.
• cytomegalovirus
  • The cytomegalovirus (CMV) can cause several types of infection, which usually aren't serious in people with normal immune systems. This virus can also remain dormant in the body for many years and cause recurring infections.
  • CMV infections in people with weakened immune systems can cause serious health problems like pneumonia, intestinal infection (enteritis) or hepatitis.

Fungal infections

Fungi can pose a problem for people with weakened immune systems. The most common fungal infection in people with cancer is thrush, which is an infection of the mouth caused by the fungus Candida. Candida can also grow in a woman's vagina and cause vaginal thrush.

Protozoan infections

Protozoa can cause serious infections in people whose immune systems have been weakened by an organ transplant, cancer or other immune-suppressing illnesses. Toxoplasmosis is a serious protozoan infection that can damage the brain or heart.

Back to top

Diagnosis

The doctor will take a medical history, which is a record of present symptoms the person has. A physical examination allows the doctor to look for any signs of infection.

Certain tests are done to find out the source of infection. Cultures are done to identify the organism causing the infection. Samples from the site of infection are put on a special gel or in a broth to see what organisms grow. Sensitivity testing involves using samples of different antibiotics on the organisms to help identify which antibiotic would work best. Together, these tests are called culture and sensitivity (C&S). Gram stain tests may also be done. Gram staining involves taking samples from the suspected site of infection, treating them with certain stains (dyes) that make the bacteria easier to see, and looking at them under a microscope. This can provide information about the type of organism. It may take between 24 and 48 hours until test results are available.

Diagnostic tests may include:

• blood tests
  • complete blood count (CBC) – may indicate an infection
  • blood cultures to check if an organism is causing an infection in the blood
• urinalysis or urine cultures to check for a urinary tract infection
• cultures of mouth sores, skin or wound sores, intravenous sites or vascular access devices to check if these are sources of infection
• chest x-ray or a sample of sputum to check for pneumonia
• stool samples, if the person is having diarrhea, to check for infection in the gastrointestinal tract
• other imaging tests to check for pockets of infection or abscesses

Back to top

Prevention

A drug to fight bacterial infections (an antibiotic) or other infection-fighting drugs (such as antiviral or antifungal drugs) may be ordered if the WBC count becomes too low and the healthcare team feels the risk of developing an infection is high. Giving drugs to prevent an infection is called prophylaxis.

In some cases, colony-stimulating factors (CSFs) may be ordered to help stimulate the bone marrow to produce more blood cells.

Precautions

Infections can occur even if everything possible is done to protect the person. But a person can take steps to lower their risk of getting an infection.

• Practise good personal hygiene. This is one of the most effective ways of avoiding infection.
  • Wash hands frequently with soap and water.
  • Always wash hands when preparing food.
  • Family members should always wash their hands when returning home from school, shopping or work.
  • Have a shower, sponge bath or bath to decrease the amount of bacteria on the skin.
  • Use lotions and moisturizers on the skin to prevent drying, chapping and cracking.
• Whenever possible, get enough rest, eat a well-balanced diet, drink plenty of fluids and get regular exercise.
• Avoid large crowds and anyone with signs of an infection, such as fever, cough, sneezing, cold sores, diarrhea and vomiting, when blood cell counts are low. Let the healthcare team know if you have come in contact with anyone suspected of having or diagnosed with chicken pox, measles or mumps when your immune system is weak.
• Protect your skin from cuts and scrapes. Protect your hands and feet from cuts and injury. Wash cuts right away with soap and water and keep them clean.
• Keep a close watch on your mouth, anal area, biopsy and surgery sites, and areas of injury, such as cuts in the skin.
• Practise food safety to reduce the chance of contaminating food.
• Do not share items such as spoons, forks, glasses or cups.
• Use sunscreen, wear a hat or scarf, and find shady areas to avoid sunburn.
• Do not play or swim in ponds, lakes or rivers.
• Avoid contact with stool and urine from pets and other animals.
• Practise good mouth and dental hygiene. Check all surfaces of your mouth for sores each day.
  • A mouthwash may be ordered during chemotherapy to kill bacteria.
  • Replace toothbrushes every 3 months to reduce the chance of infection in the mouth.
  • Get a new toothbrush after treating a mouth infection.
  • Plan dental checkups or dental procedures when blood cell counts are normal and you are at less risk of infection.
• If you have a venous access device, such as a central venous catheter or peripherally inserted central catheter (PICC), follow instructions on caring for these devices.
• Avoid rectal thermometers, suppositories and enemas. These can add to the risk of infection by introducing bacteria through tiny tears in the anus or rectum. Avoid constipation since straining can also cause small tears in the anus.
• Talk to your healthcare team about immunizations (vaccinations). Depending on your treatment, there may be some vaccinations you should avoid and others you should have. In general, “killed” vaccines such as the flu, pneumococcal and tetanus vaccines can safely be given. However, “live” vaccines, such as the measles or mumps vaccine, may not be safe.

Back to top

Treatment

Fever and neutropenia in people with cancer is a medical emergency that needs immediate attention and treatment. The chance of an underlying infection in a person with neutropenia and fever increases with the severity of the neutropenia. Infections can be life-threatening if they lead to a condition called septic shock.

It is important to contact the healthcare team if you have any signs or symptoms of an infection. Infections in a person with a weakened immune system need to be treated as quickly as possible. Antibiotics are started, and tests such as cultures are done to try to identify the organism causing the infection. The person is usually started on a broad-spectrum antibiotic before the test results are known since infections can spread quickly. Broad-spectrum antibiotics are directed against many organisms that could be causing the infection. Once the cause of infection is identified, the antibiotic may be changed to one that is specifically used to treat a particular organism.

The doctor will select an antibiotic based on the person's history, symptoms, allergies, recent antibiotic use and test results. For most infections, antibiotic treatment will continue for 7 to 14 days depending on the:

• cause of infection
  • Treatment depends on the organism causing the infection. Different drugs are used to treat different types of organisms. These can be antibiotic, antiviral, antifungal or other drugs.
• person's overall condition
• person's response to treatment

If the infection does not respond after 3 to 5 days, the healthcare team may decide to add more drugs or change the drugs.

Doctors try not to overuse antibiotics because some bacteria can become resistant to them and will not be killed by the same antibiotic that worked before (antibiotic resistance).

Back to top

Managing a fever

Fever over 38°C is the most common sign of an infection. A fever is the body's way of protecting itself. When foreign substances such as germs enter the body, the body releases substances called cytokines to increase the temperature and make the immune system work better.

The surface air feels cooler as the body temperature increases, causing the body to shiver. Shivering occurs when the muscles contract to produce more heat. As the body temperature increases, it produces a fever. A fever can be lowered by taking acetaminophen (Tylenol), by helping the body get rid of heat and by correcting or preventing dehydration.

• Acetaminophen will not treat what is causing the fever but will help to lower the temperature and make the person more comfortable. Do not take acetaminophen unless the doctor says it's okay. Drugs can mask a fever, and it is important for the healthcare team to be aware of the fever and to treat the infection that is causing it.
• Do not take Aspirin or ibuprofen (Advil, Motrin) since these drugs promote bleeding, especially in the gastrointestinal tract. A person having chemotherapy is at a higher risk of bleeding.
• Take other medications prescribed for fever or infection as ordered by the doctor.
• Keep warm and cover up with a blanket if you have chills or shaking. Once you stop shivering, remove layers one at a time.
• Remove heavy clothing and dress in light clothing that allows air to pass through to the skin and doesn't trap body heat. Cover up with a light sheet and put a cool washcloth on your forehead if you feel hot.
• Drink cool fluids every hour to prevent dehydration.
• Change damp clothing and bed linens to prevent getting chilled.

Shaking chills

Shaking chills (rigors) occur when the body shakes because it is cold. They are similar to shivering when you have an infection and fever, but much more intense. A person may get rigors from a very bad infection, some drugs or sometimes during a blood transfusion.

Let the healthcare team know what is happening right away and keep warm.

Back to top