This chapter is a continuation of the previous chapter.

Viral Infections

A virus is a pathogen with a nucleic acid molecule within a protein coat. It requires a living host for replication. An invading virus may immediately cause disease or may remain relatively dormant for years. Diseases develop as a result of interference with the normal cellular functioning of the host, with the destruction of the virus by the immune system also requiring the death of the host cell.

1. Human immunodeficiency virus (HIV): Human Immunodeficiency Virus (HIV) is a retrovirus that attacks the body’s immune system, specifically the CD4 cells (T cells), which are crucial for immune function. If left untreated, HIV can lead to Acquired Immunodeficiency Syndrome (AIDS), the most severe phase of HIV infection, where the immune system is severely compromised, making the body vulnerable to opportunistic infections and certain cancers. Antiretroviral therapy is used for pharmacologic management of HIV.

    HIV Infection

   Pathophysiology

   1. Entry and Infection: HIV targets and enters CD4 cells by binding to the CD4 receptor and co-receptors (CCR5 or CXCR4) on the cell surface. Once inside the cell, the viral RNA is reverse-transcribed into DNA by the enzyme reverse transcriptase.

   2. Integration: The enzyme integrase then integrates the newly synthesized viral DNA into the host cell’s genome. This allows the virus to hijack the host cell’s machinery to produce new viral particles.

   3. Replication: The infected CD4 cell produces viral proteins and RNA assembled into new virions. These new virions are then released from the host cell, ready to infect other CD4 cells.

   4. Immune System Impact: Over time, HIV reduces the number of CD4 cells, weakening the immune system. This depletion leads to increased susceptibility to opportunistic infections and certain cancers, which define the progression to AIDS if left untreated.

   Stages of HIV Infection

   1. Acute HIV Infection: This is the initial stage of infection, occurring 2 to 4 weeks after exposure. Symptoms of the flu may resemble fever, swollen lymph nodes, sore throat, rash, muscle and joint aches, and headache. High levels of virus are present in the blood, making the individual highly infectious.

   2. Chronic HIV Infection: Also known as the asymptomatic or clinical latency stage, this period can last for several years. The virus is still active but reproduces at very low levels. Individuals may not have symptoms but can still transmit the virus.

   3. AIDS: Without treatment, chronic HIV infection typically progresses to AIDS in about ten years. The immune system is severely damaged at this stage, and the body becomes susceptible to opportunistic infections and cancers. Common symptoms include rapid weight loss, recurring fever, chronic diarrhea, sores, pneumonia, and memory loss.

   References:

   National Institute of Allergy and Infectious Diseases (NIAID). (2021). HIV/AIDS Overview. Retrieved from NIAID

   World Health Organization (WHO). (2021). HIV/AIDS. Retrieved from WHO

2. Hepatitis A, B, C, or E: Hepatitis viruses are a group of viruses that cause liver inflammation. There are five main types: Hepatitis A(HAV), Hepatitis B (HBV), Hepatitis C (HCV), hepatitis D(HDV), and Hepatitis E( HEV). A different virus causes each type and has unique modes of transmission, severity, and outcomes.

3. Human papillomavirus (HPV) is a common viral infection with more than 200 related viruses. It is primarily transmitted through intimate skin-to-skin contact, often during sexual activity. HPV can affect the genital areas, mouth, and throat. Most HPV infections are asymptomatic and resolve on their own. However, some strains can cause warts, and others are associated with cancers, such as cervical, anal, and oropharyngeal cancers. Vaccines are available to protect against the most harmful types of HPV, significantly reducing the risk of associated cancers and genital warts  ( CDC, 2024; WHO, 2024)

4. Respiratory syncytial virus (RSV) is a common respiratory virus that typically causes mild, cold-like symptoms. However, it can be severe, especially in infants and older adults. RSV is a leading cause of bronchiolitis and pneumonia in children under one year old. The virus spreads through respiratory droplets when an infected person coughs or sneezes. Most children are infected with RSV by age two, and reinfections can occur throughout life. There is no specific treatment for RSV, but supportive care, such as hydration and oxygen therapy, can help manage symptoms. Preventive measures include good hygiene practices and, for high-risk infants, a monthly injection of palivizumab during RSV season.

5. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the novel coronavirus responsible for the COVID-19 pandemic, which began in late 2019. It primarily spreads through respiratory droplets when an infected person coughs, sneezes, or talks. The virus can cause a range of illnesses, from mild respiratory infections to severe pneumonia, acute respiratory distress syndrome (ARDS), and death. Common symptoms include fever, cough, and shortness of breath, but can also include loss of taste or smell, fatigue, and gastrointestinal issues. Preventive measures include wearing masks, practicing social distancing, frequent hand washing, and vaccination. Vaccines have been developed and distributed globally to combat the spread and impact of COVID-19.

General Symptoms of Viral Infection

Viral infections often present with various general symptoms varying in severity and duration. Common symptoms include fever, fatigue, headache, muscle and joint aches, and malaise. Respiratory symptoms such as cough, sore throat, nasal congestion, and runny nose are typical, especially in infections like the flu or the common cold. Gastrointestinal symptoms, including nausea, vomiting, diarrhea, and abdominal pain, may occur in viral gastroenteritis. Additionally, viral infections can cause skin rashes and lymphadenopathy (swollen lymph nodes). Symptoms can vary based on the specific virus, the affected body system, and the individual’s immune response.

Comparison of General Symptoms: Bacterial vs Viral Infections

III. Fungal Infections

A fungus is any spore-producing microorganism, which includes yeasts, molds, and mushrooms. Fungi typically grow and proliferate in moist areas of the body, such as between the toes, in the groin, under the panniculus, and under the breasts. In an otherwise healthy individual, fungi do not cause disease and are contained by the body’s natural flora.  In the immunocompromised individual, they can result in infections that lead to death.  Obese people and people with diabetes are also more susceptible to fungal infections.

Common fungal infections:

1. Tinea pedis (athlete’s foot):  this infection can occur in healthy individuals as well
2. Candidiasis (yeast infection)
3. Aspergillosis (lung infection caused by mold)
4. Histoplasmosis (fungal lung infection)

IV. Parasitic Infections

Parasites or protozoa generally infect individuals with compromised immune responses. They are typically found in dead material in water and soil and are spread by the fecal-oral route by ingesting food or water contaminated with parasitic spores or cysts. The disease may develop in an otherwise healthy individual when the spores invade organs and stimulate an immune response, interfering with the normal functioning of the organ system.

Common parasitic infections:

• Giardiasis
• Cryptosporidium
• Toxoplasmosis
• Malaria

III. Clinical Reasoning and Decision-making: Pharmacologic Management of Infections

The previous sections were reviews of antimicrobial basics. The next sections will take a closer look at specific classes of drugs used to treat infections ( anti-infectives) and administration considerations, therapeutic effects, adverse effects, and specific patient teaching. This unit examines the importance of the nursing process in guiding the nurse who administers anti-infective medications.  The nursing process consists of assessment, diagnosis, outcome identification, planning, implementation of interventions, and evaluation. These basic steps lead to sound clinical reasoning and safe decision-making in administering drugs related to infection.

Assessment: Although there are numerous details to consider when administering medications, it is always important to think more broadly about what you are giving and why.  As a nurse administering an antimicrobial, you must remember some important broad considerations.

Antimicrobials are given to prevent or treat infection. If a patient is prescribed an antimicrobial, an important piece of the nursing assessment is to recognize and analyze cues. The nurse should look for signs and symptoms of infection and always know WHY the patient receives an antimicrobial to evaluate whether the patient is improving or deteriorating effectively. Remember, the nurse must assess how this medication is working, and having pre-administration assessment information is an important part of this process.

To define a baseline, typical data that a nurse collects at the start of a shift include:

• temperature
• heart rate
• blood pressure
• respiratory rate, and
• white blood cell count.
• Focused assessments are then made based on the type of infection. For example, if it is a wound infection, the wound should be assessed for redness, inflammation, drainage type and amount, and pain. If it is a respiratory infection, the nurse should assess the patient’s lung sounds and type/consistency of respiratory expectorate. If a patient has a urinary tract infection (UTI), the urine and symptoms related to a UTI (pain with urination, cloudy urine, foul-smelling urine) should be assessed.
• The following image summarizes some common signs and symptoms of infection (by system) that a nurse needs to monitor for.

Additionally, whenever a patient has an infection, it is important to continually monitor for the development of sepsis, a life-threatening condition caused by severe infection.  As you recall from the previous chapter, early signs of sepsis include new-onset confusion, elevated heart rate, decreased blood pressure, increased respiratory rate, and elevated fever.

Additional baseline information to collect before administering any new medication order includes patient history, current medication use, including herbals or other supplements, and history of allergy or a previous adverse response. Many patients with an allergy to one type of antimicrobial agent may experience cross-reactivity to other classes. This information should be appropriately communicated to the prescribing provider before administering any antimicrobial medication.

When nurses have completed a thorough assessment, they can prioritize their concerns/hypotheses before implementing further intervention.

Interventions

When administering the antimicrobial medication, the nurse needs to anticipate any additional interventions associated with the medications. For example, antimicrobials often cause gastrointestinal upset (GI), such as nausea, diarrhea, etc.  The nurse may need to refine their assessments and interventions accordingly. The patient should be educated about these potential side effects, and proper interventions should be taken to minimize these occurrences. For example, the nurse may instruct the patient to take certain antimicrobials with food to

diminish the chance of GI upset, whereas other medications should be taken on an empty stomach for optimal absorption.

Hypersensitivity/allergic reactions are always a potential adverse reaction, especially when administering the first dose of a new antibiotic, and the nurse should monitor closely for these symptoms and respond appropriately by immediately notifying the prescriber.  Hypersensitivity reactions are immune responses that are exaggerated or inappropriate to an antigen and can range from itching to anaphylaxis.  Anaphylaxis is a medical emergency that can cause life-threatening respiratory failure.  Early signs of anaphylaxis include, but are not limited to, hives and itching, the feeling of a swollen tongue or throat, shortness of breath, dizziness, and low blood pressure.

Evaluation

Finally, it is important to evaluate the patient’s response to a medication. With antimicrobial medications, the nurse should assess for the absence of or decreasing signs of infection, indicating the patient is improving. It is important to document these findings to reflect the patient’s trended response.

It is also important for the nurse to promptly identify and communicate signs of worsening infection to the provider. For example, increasing white blood cell count, temperature, heart rate, and respiratory rate may indicate that the patient’s body is experiencing a life-threatening response to the infection. These signs of worsening clinical assessment require prompt intervention to prevent further clinical deterioration. Additionally, patients receiving antibiotics should be closely monitored for developing a complication called “C. diff,” resulting in frequent, foul-smelling stools. C. diff stands for Clostridioides difficile, a spore-forming, gram-positive bacterium that colonizes the human intestinal tract after the normal gut flora has been disrupted (frequently associated with antibiotic therapy). C. diff is one of the most common healthcare-associated infections and a significant cause of morbidity and mortality, especially among older adult hospitalized patients. Management of C-diff requires the implementation of modified contact precautions, including using soap and water, not hand sanitizer (as this does not kill the spores), and antibiotic therapy.

Administration Considerations

Antimicrobial drug therapy involves special considerations to ensure the therapeutic drug effect is achieved while maintaining patient safety and minimizing complications.

Let’s consider some of the variables that may impact antimicrobial administration:

Half-Life

Many antimicrobial medications are administered to ensure that a certain therapeutic level of medication remains in the bloodstream and may require interval or repeated dosing throughout the day. For example, the half-life, or rate at which 50% of a drug is eliminated from the plasma, can vary significantly between drugs. Some drugs have a short half-life of only 1 hour and must be given multiple times a day, but other drugs have half-lives exceeding 12 hours and can be given as a single dose every 24 hours. Although a longer half-life can be considered an advantage for an antibacterial when it comes to convenient dosing intervals, the longer half-life can also be a concern for a drug with serious side effects. Medications with a longer half-life and more concerning side effects will exert these side effects over a longer period.

See the figure below for an illustration of half-lives and the time it takes for a medication to be eliminated from the bloodstream.

Lifespan Considerations

Most medications are calculated specifically based on the patient’s size, weight, and renal function. Patient age and size are especially vital in pediatric patients. A child’s stage of development and the size of their internal organs greatly impact how the body absorbs, digests, metabolizes, and eliminates medications.

Liver & Renal Function

Additionally, many antimicrobial medications require tailored dosing based on individual patient responses and the potential impact of the medication on the patient’s liver and renal function. For more information about the effects of liver and renal function on medications, refer to Chapter 1 regarding metabolism and excretion.

Often, pharmacists and providers collect peak and trough drug blood levels to determine how an individual patient’s body responds to an antimicrobial. Follow-up interval dosing is then prescribed based on these blood levels. This is especially important for older adults or those with known liver/renal impairment. Individuals with diminished liver and renal function are more prone to drug toxicity because of the reduced ability of the body to metabolize or clear medications from the body. For more information about peak and trough levels, refer to Chapter 1 regarding medication safety.

Dose Dependency/Time Dependency

The goal of antimicrobial therapy is to select an optimal dosage that will result in a clinical cure while reducing complications or significant side effects. Many medications may be dose-dependent. This means there is a more significant killing of bacteria with increasing levels of antibiotics.  For example, fluoroquinolones are dose-dependent medications with the treatment goal of optimizing the amount of the drug. Other medications are time-dependent. Time-dependent medications have optimal bacterial-killing effects at lower doses over a longer period of time. Time-dependent antimicrobials exert the greatest effect by binding to the microorganism for an extensive length of time.  Penicillin is an example of a time-dependent medication that aims to optimize the duration of exposure.

Route

It is also important to consider the route of drug administration within the patient’s body. Many of us may have been prescribed oral antibiotics and have filled our prescriptions and completed the drug regimen within the comfort of our own homes. However, many types of infections or disease processes do not respond well to the use of oral antimicrobial therapy. For these diseases, patients may require intravenous or intramuscular injections. Patients requiring intravenous or intramuscular injections may need to be hospitalized, have home health nursing arranged, or travel to the hospital/clinic for their therapy. Concerns with treatment compliance exist with all routes of administration.  For more information about considerations regarding routes of administration, refer to Chapter 1 on absorption. The figure below is an illustration of three common routes of antimicrobial medications within the body:

Drug Interactions

Two antibacterial drugs may be administered together for the optimum treatment of select infections. Concurrent drug administration produces a synergistic interaction that is better than the efficacy of either drug alone. In this case, two is truly better than one! A classic example of synergistic drug combinations is trimethoprim and sulfamethoxazole (Bactrim). Individually, these two drugs provide only bacteriostatic inhibition of bacterial growth, but combined, the drugs are bactericidal.

Although synergistic drug interactions benefit the patient, antagonistic interactions produce harmful effects. Antagonism can occur between two antimicrobials or between antimicrobials and non-antimicrobials being used to treat other conditions. The effects vary depending on the drugs involved. Still, antagonistic interactions cause diminished drug activity, decreased therapeutic levels due to elevated metabolism and elimination, or increased potential for toxicity due to decreased metabolism and elimination.

Let’s consider an example of these antagonistic interactions.

Many antibacterials are absorbed most effectively from the stomach’s acidic environment. However, if a patient takes antacids, the antacids increase the stomach’s pH and negatively impact the absorption of the antibacterial, thus decreasing their effectiveness in treating an infection.

IV. Pharmacologic Management of Infections: Antibacterials

Antibacterial management is a critical aspect of healthcare and nursing practice, focusing on the effective use of antibiotics to treat bacterial infections while mitigating the risk of antibiotic resistance. This involves a responsible selection of appropriate antibiotics, accurate dosing, careful treatment efficacy, and patient response monitoring. Key elements to consider in this practice include stewardship programs that promote the responsible use of antibiotics, education of healthcare providers and patients about the dangers of overuse and misuse, and adherence to infection prevention protocols to reduce the spread of resistant bacteria. Additionally, it is essential for healthcare professionals to stay informed about the latest research and guidelines on antimicrobial resistance and to implement evidence-based practices in clinical settings. Effective antibacterial management enhances patient outcomes and supports public health by preserving the efficacy of existing antibiotics.

Nurses play pivotal roles in the effective and safe management of antibacterial treatments, which are integral to controlling infections and preventing the escalation of antibiotic resistance. Their responsibilities include:

1. Patient Education: Nurses educate patients on the proper use of antibiotics, including adherence to prescribed dosages and schedules, the importance of completing the full course even if symptoms improve, and the risks associated with misuse.
2. Monitoring and Compliance: They closely monitor patients for signs of improvement or side effects, ensuring compliance with treatment protocols. This vigilance helps adjust treatments as needed in consultation with physicians, optimize therapeutic outcomes, and minimize adverse effects.
3. Infection Control: Nurses implement rigorous infection control measures in healthcare settings to prevent the spread of infections and reduce the need for antibiotics, thus helping to decrease the development of resistance.
4. Stewardship Advocacy: Nurses advocate for the judicious use of antibiotics within antimicrobial stewardship programs. They collaborate with the healthcare team to select the most appropriate antibiotic therapy based on current guidelines and individual patient needs.
5. Data Collection and Reporting: Nurses contribute to the surveillance of antibiotic efficacy and resistance by collecting and reporting data on antibiotic use and resistance patterns. This information is crucial for ongoing evaluation and improvement of treatment protocols.
6. Interdisciplinary Collaboration: Nurses collaborate with a multidisciplinary team, including pharmacists, physicians, and infection control specialists, to ensure a coordinated approach to antibacterial management. This maximizes the effectiveness of interventions to manage infections and prevent antibiotic resistance.

By fulfilling these roles, nurses ensure that antibacterial management is both effective and safe, thereby safeguarding patient health and contributing to global efforts to combat antibiotic resistance. Nurses can competently perform these roles with pharmacologic knowledge of antibiotics.

V. Pharmacologic Management of Infections: Antibacterials

Antiviral management is a crucial component of healthcare and nursing practice, focusing on effectively using antiviral medications to treat viral infections, prevent the spread of viruses, and mitigate the impact of viral diseases. This management requires a comprehensive approach that includes accurate diagnosis, timely initiation of therapy, and ongoing monitoring of treatment efficacy and patient adherence. Key elements to consider include understanding the mechanisms of action of antiviral drugs, the potential for resistance development, and the appropriate use of these medications in specific populations such as the immunocompromised. Nurses play a vital role in antiviral management by educating patients on the importance of adhering to prescribed treatment regimens, monitoring for adverse reactions and effectiveness of the therapy, and implementing infection control measures to prevent transmission. Additionally, nurses must stay informed about the latest developments in antiviral treatments and evolving viral threats to provide the most up-to-date care for their patients and advise on preventive measures, including vaccination, where available. Effective antiviral management improves patient outcomes and contributes to the broader public health goal of controlling viral diseases. Nurses are integral to the successful pharmacologic management of antiviral therapies, playing several critical roles that enhance patient outcomes and ensure the safe and effective use of antiviral medications.

Unlike the complex structures of fungi or protozoa, viral structures are simple. Antiviral medications have several subclasses: antiherpes, anti-influenza, anti-hepatitis, and antiretrovirals. Each subclass will be discussed in more detail below.

 Images of viruses.

Images of Viruses (a) Members of the Coronavirus family can cause respiratory infections like the common cold, severe acute respiratory syndrome (SARS), and Middle East respiratory syndrome (MERS). Here, they are viewed under a transmission electron microscope (TEM).
(b) Ebolavirus, a member of the Filovirus family. (credit a: modification of work by Centers for Disease Control and Prevention; credit b: modification of work by Thomas W. Geisbert)

Antinfluenza

• Mechanism of Action: Tamiflu prevents the release of virus from infected cells. The influenza virus is one of the few RNA viruses that replicate in the nucleus of cells. Antivirals block the release stage.

Influenza Virus Replication Stages

• Indications: Oseltamivir (Tamiflu) targets the influenza virus by blocking its release from the infected cells.
• Nursing Considerations: This medication does not cure influenza but can decrease flu symptoms and shorten the duration of illness if taken within 48 hours of symptom onset. Patients are prescribed the medication for prophylaxis against infection, known exposure, or to lessen the course of the illness. Patients who experience flu-like symptoms must start treatment within 48 hours of symptom onset.
• Side Effects/Adverse Effects: Common side effects include GI upset. Adverse effects include serious skin hypersensitivity reactions or neuropsychiatric symptoms, especially in children. Use cautiously in patients with renal failure, chronic cardiac or respiratory diseases, or any medical condition that may require imminent hospitalization.
• Health Teaching & Health Promotion: Patients treated with antiviral therapy should be instructed about the importance of medication compliance. They may also experience significant fatigue, so rest periods should be encouraged.

Antihepatitis

• Viruses with complex life cycles, such as HIV, can be more difficult to treat. These viruses require antiretroviral medications that block viral replication, often called antiretroviral therapy (ART). Additionally, antiretrovirals fall under the class of antiviral medications.

•  HIV attaches to an immune cell’s cell surface receptor and fuses with the cell membrane. Viral contents are released into the cell, where viral enzymes convert the single-stranded RNA genome into DNA and incorporate it into the host genome.
• Mechanism of Action: Antiretrovirals impede virus replication.
• Indications: Antiretrovirals such as lamivudine-zidovudine are used for the treatment of illnesses like HIV.
• Nursing Considerations: Many antiretrovirals may impact renal function; therefore, the patient’s urine output and renal labs should be monitored carefully for signs of decreased function.
• Side Effects/Adverse Effects: Adverse side effects of antiretroviral medications include lactic acidosis and severe hepatomegaly. Patients should cease medication immediately if pancreatitis occurs.
• Health Teaching & Health Promotion: Patients treated with antiviral therapy should be instructed about the importance of antiretroviral compliance. They may also experience significant fatigue, so rest periods should be encouraged.

Acyclovir Medication Grid

Oseltamivir Medication Grid

Adefovir Medication Grid

Lamuvadine-Zidovudine Medication Grid

VI. Pharmacologic Management of Infections: Antifungals

Fungi are important to humans in a variety of ways. Microscopic and macroscopic fungi have medical relevance, but some pathogenic species can cause mycoses (illnesses caused by fungi). See Figure below for a microscopic image of Candida albicans, the causative agent of yeast infections. Some pathogenic fungi are opportunistic, meaning they mainly cause infections when the host’s immune defenses are compromised and do not normally cause illness in healthy individuals. Fungi are also major sources of antibiotics, such as penicillin from the fungus Penicillium.

 

VII. Pharmacologic Management of Infections: Anthelmintics

VIII. Getting-it-together: Clinical Application

References:

Abbas, A. K., Lichtman, A. H., & Pillai, S. (2017). Cellular and Molecular Immunology (9th ed.). Elsevier.

Centers fo

 Disease Control and Prevention. (2022). Chain of Infection. Retrieved from https://www.cdc.gov/infectioncontrol/index.html

Elmore, S. (2007). Apoptosis: A Review of Programmed Cell Death. Toxicologic Pathology, 35(4), 495-516. DOI:

Delves, P. J., Martin, S. J., Burton, D. R., & Roitt, I. M. (2017). Roitt’s Essential Immunology (13th ed.). Wiley-Blackwell.

Giddens, J. (2017). Concepts for Nursing Practice (2nd ed.). Elsevier.

Janeway, C. A., Travers, P., Walport, M., & Shlomchik, M. J. (2001). Immunobiology: The Immune System in Health and Disease (5th ed.). Garland Science.

Murray, P. R., Rosenthal, K. S., & Pfaller, M. A. (2016). Medical Microbiology (8th ed.). Elsevier

Murphy, K., & Weaver, C. (2016). Janeway’s Immunobiology (9th ed.). Garland Science.

Plotkin, S. A., Orenstein, W. A., & Offit, P. A. (2010). Vaccines (5th ed.). Saunders.

World Health Organization. (2022). Infection prevention and control. Retrieved from https://www.who.int/teams/integrated-health-services/infection-prevention-control

Attributions:

This chapter is designed as a learning material for students in fundamentals of nursing level and is largely attributed to:

https://collection.bccampus.ca/textbooks/fundamentals-of-nursing-pharmacology-a-conceptual-approach-1st-canadian-edition-bccampus-400/#license

Several topic overviews are linked to to the  Merck Manuals Professionals – Health & Medical InformationMerck Manualshttps://www.merckmanuals.com/