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Clinical Immunology & Microbiology: Case Study


The human body has a distinct structural configuration, usually with chemical barriers to pathogens. It has an innate immune system, an immunological mechanism that fights and responds to intruding pathogens. The immune response is usually initiated minutes after a pathogenic attack on the body system. A deeper understanding of this concept is through clinical immunology and microbiology, whereby epidemiologic, basic, and clinical science and research are conducted into human immunologic infectious and inflammatory disease. For better understanding, this report focuses on a case study of a 29-year-old female, Akua, from Botswana, who presents symptoms of a pathogenic attack on the immune system. It will mainly focus on the diagnosis, symptoms, structural life cycle of the infectious agents, modes of transmission, and a detailed outlook on HIV infection, the primary disease in this case.

Diagnosis for the Patient’s Initial Infectious Disease and the associated Symptoms

In the case of Akua, she presented at a medical centre complaining of a fever that had started 14 days earlier, accompanied by nausea and muscle pain. Upon questioning, it is clear that the fever is episodic and mostly linked to shaking and sweating. In febrile conditions, the evaluation of a carefully obtained and detailed history is invaluable. This makes the aetiology evident from the physical examination and history alone. The patient’s physical examination results show that the pulse rate is higher than normal. The temp is also high, a possible cause of the fever. Also, the ESR indicates 85 mm/h, which is considered high and may point to some infection. The results show Albumin is below the normal range of 34 to 54 g/l, and the bilirubin level is too high.

Considering these results, including the palpable liver and spleen, pale mucous membrane, shaking, sweating, muscle pain, and nausea, a possible diagnosis for this infection is the onset of Hepatitis A. This is because common Hepatitis A symptoms include fever, rigours, nausea, splenomegaly, hepatomegaly, chills, muscle pains, and night sweats. The patient had a recent travel history from Africa to the U.K. Since the Hepatitis A virus is an enterically spread Picornavirus endemic in developing countries such as Botswana, in Akua’s case, she may likely have been exposed to the infection. The infection mostly attacks the liver, where red blood cells are made. Destruction of red blood cells is possible after infection due to altered levels of liver functions, as seen in the tests. It is the most likely cause of pale skin and anaemia.

In addition, this is also the cause of splenomegaly and hepatomegaly. Anaemia and low blood sugar, as indicated by the blood test results of glucose at 3.2 mmol/L, are common complications of a liver infection. The low glucose suggests possible hypoglycemia, which could also be accelerating sweating, shaking, and headache. A differential diagnosis, in this case, could be Malaria considering her recent travelling from Africa, where it is endemic. Also, both infections present almost similar symptoms, but we rule out Malaria since protozoa cause it while Hepatitis is viral. Also, there is a remarkable increase in Bilirubin in Hepatitis patients, as seen in the case of Akua.

Abnormalities in Tests and Investigation Results

While the blood pressure reading of 100/65 and creatinine are within the normal range, several other test results show abnormalities in the patient. The platelet level is significantly low, which signals an infection with bacteria, protozoa, and viruses, in this case, Hepatitis A. The MCV reads 72fl, below the normal range of about 80-100fl. People with such low MCV levels, as seen during Akua’s physical examination, develop microcytic anaemia. This is because of altered liver functions. Generally, changes in liver function tests are common indicators of a disease like liver cirrhosis, drug side effects, or viral or Hepatitis.

From the results of the liver test, the AST level is high. When it increases, like in Akua’s case, it indicates liver damage or disease. Bilirubin levels are also elevated in the patient. When this happens, it points to liver disease, damage, and certain types of anaemia. The patient’s albumin levels are also too low, indicating possible liver disease or damage. The blood test results also help in supporting this diagnosis. For instance, the glucose level indicates likely hypoglycemia induced by glycogen depletion due to Hepatitis A-induced liver disease. In addition, elevated ESR indicates autoimmune disorders, infections, anaemia in this case, or some kidney problems. The anaemia in the patient is also detected in the blood test by the low MCV level, usually microcytic anaemia, and the low Hb of 90g/l.

Treatment Regimen for the Initial Diagnosis of an Infection

Liver function tests are used to screen for infections such as Hepatitis. The tests help to determine the appropriate diagnosis and treatment. In the case study presented, the initial diagnosis points to a possible onset of Hepatitis A. Generally, after diagnosis, there is no specific treatment that exists for Hepatitis A. In most cases, the body clears the infection on its own, and the liver heals within a few weeks to six months. The most appropriate treatment regimen for Akua would involve staying comfortable and controlling symptoms. She needs to rest since most Hepatitis A patients feel tired, sick, and have less energy. The patient should also take adequate liquids and food to get enough calories. This should involve a balanced diet, although nausea can make eating challenging. Alternatively, she could focus on snacking throughout the day instead of eating full meals.

She can focus on drinking milk or fruit juice instead of water and make sure she drinks a lot of fluids to prevent dehydration, especially when vomiting occurs. In her treatment plan, it is vital to indicate the avoidance of alcohol. Additionally, she should use medications with care. This is because the liver may have difficulties processing alcohol and medications due to the infection. Alcohol may also accelerate liver damage. Moreover, if a person thinks they are exposed to Hepatitis A, they should immediately see a doctor. Also, people exposed to the infection should get a drug or vaccine called Hepatitis A immune globulin. However, for this to work, a person should get the vaccine immediately after exposure to the virus.

Structure and Life Cycle of the Infectious Agents and the Relationship with the Clinical Presentation

Hepatitis A (HAV) is a highly contagious liver infection caused by a virus. This virus is among the many Hepatitis viruses that affect the liver, causing inflammation and interfering with its normal functioning, thus presenting unfavourable effects as presented by the patient. A person is likely to get the infection through contaminated food and water. The virus is usually in the genus Hepatovirus an enteric of the family Picornaviridae, and its genome is a single-stranded RNA molecule of positive-strand polarity (McKnight and Lemon, 2018). The polyprotein code sequence is processed to give rise to viral proteins VP-1, VP-2, and VP-3, among others. In contrast to other picornaviruses, HAV does not shut down cellular synthesis of protein in infected cells and replicates without cytopathic effect.

After contracting the virus, the incubation period of illness is about 15 to 45 days, roughly 30 days. After entry, the virus loses the capsid, and the uncoated RNA induces viral polyprotein in the host cell without shutting down the protein synthesis of the cell. HAV replicates in the liver and is usually excreted in high concentrations in the bile and stool. The replication in the liver cells causes inflammation, thus affecting how the liver works. This usually interferes with the regulation of vital components such as Bilirubin which becomes elevated, as observed in the patient.

Since the virus replicates its protein strand, it causes lower levels of Albumin, essential in fighting infections. This may explain why the levels are low in Akua’s test results. In addition, it interferes with the production of red blood cells, which may lead to anaemia and glucose levels which is the possible cause of the low levels in the patient, indicating hypoglycemia. The virus infectivity in stool is present 21 days before to 8 days after the onset of jaundice. Hepatitis A usually begins with a mild prodrome. After one to seven days, dark urine may appear, which may explain the high urea seen in the Akua.

Modes of Transmission and the Immune responses to the Pathogens

Generally, Hepatitis A is transmitted through contaminated water and food consumption. It is also spread through direct contact with an infected person. The body’s immune system responds to the virus by attacking it to prevent it from further replication, resulting in liver inflammation and damage. This happens when the immune system, while fighting the virus, may mistake the liver tissues for an invader and attacks them, leading to inflammation and the unfavourable symptoms observed in Akua. Geographically the distribution of high-risk areas for transmission includes low and middle-income countries like Botswana in Africa in the case study.

The primary route of transmission is the faecal-oral route. The virus is also spread through sex with an infectious person. Risk factors include poor sanitation, unprotected sexual activity with an infected person, lack of safe water, men who have sex with men, people with HIV like Akua, as it was later discovered, and also travelling to high-risk regions.

Clinical Effects of HIV Infection and why they Occur

In the case study presented, four weeks after treating Hepatitis A, the patient returns still not feeling well. She complains of low-grade fever, lymphadenopathy, and a general feeling of being unwell. Upon testing for HIV, she tests positive. HIV presents clinical effects that adversely affect the human body showing signs and symptoms as reported by Akua. HIV affects the immune system and increases the effects and risk of other infections, commonly called opportunistic infections. Due to this effect, the virus can attack or affect every part of the body, including the nervous system, skin, and respiratory. Generally, this virus gradually weakens the immune system destroying cells called CD4 T cells. When these cells are damaged, the body’s immune becomes weak over time and fails to fight off infections effectively. Typically HIV progresses through three stages.

Stage 1: Acute (Seroconversion) Infection

When one contracts the virus, the HIV amount is usually high in the blood, and the risk of transmission is high. In this stage, the infected person may experience flu-like symptoms, including fever, night sweats, tiredness or malaise, muscle pain, and nausea, like in Akua’s case. This mostly happens within 2-4 weeks of contracting the virus. These may last several days or weeks, and the virus can be spread through blood, semen, vaginal fluid, breast milk, rectal fluid, and pre-seminal fluids. The symptoms appear when the immune system tries to fight the virus. However, not everyone experiences these symptoms. Eventually, the symptoms stabilize, but the virus keeps replicating slowly.

Stage 2: Chronic (Asymptomatic) Infection

During this stage, a person may show no symptoms, but it is still replicating in the body and can be transmitted to others. If untreated, this stage can last for ten years or more without any serious symptoms. Still, if it is treated using antiretroviral therapy, it will not develop into stage three HIV, and opportunistic infections are also much lower and less severe.

Stage 3: Infection, also called AIDS

In this stage, the immune system is severely and badly damaged, and the CD4 cell count falls below 200 cells/mmof blood. The infected person becomes more vulnerable to opportunistic infections, and the viral transmission risk is usually very high. This stage, called AIDS, is the most advanced, and the immune system is damaged to the extent it cannot fight off infections. However, taking antiretroviral drugs(ARVs) prevents HIV from advancing to this stage and keeps the immune system strong.

HIV infections occur after the virus finds its way into the human body. Transmission can be mainly through sexual contact, sharing needles and razors, mother to child during breastfeeding or pregnancy, contact with infected blood, and illicit injection drug use. The virus attacks the helper T-cells of the immune system, leaving it weak.

Significance of Viral Load and CD4 Count in Relation to HIV Infection Status

Viral load indicates the amount of HIV in an infected person’s blood. Like in the case of Akua, the test results show a viral load of 255352 copies/ml. Taking ARVs can lower the viral load and improve the CD4 count. CD4 count is a test that determines how many CD4 cells are in the blood. For instance, Akua’s CD4 count indicates 155 cells/mm3. Basically, CD 4 cells are a type of white blood cell also known as CD4 T lymphocytes or helper T-cells. They help fight the infection triggering the immune system to attack and destroy bacteria, viruses, and other germs that may cause opportunistic infections.

If the viral load increases, a person’s immune system becomes weak since more CD4 cells are destroyed. However, using ARVs improves the CD4 count, and the body can fight viruses and other opportunistic infections to the point that the virus may not be detected in a test. If the viral load becomes too high, the HIV status may advance to the AIDS stage, the final and the most dangerous and difficult to manage due to the prevalence of opportunistic diseases. This is why a health advisor needs to guide the patient through counselling and the importance of high antiretroviral therapy (HAART) and post-exposure prophylaxis.

How are AIDS and HIV Infection Distinguished

HIV generally is a virus that attacks the body’s immune system. On the hand, acquired immunodeficiency syndrome (AIDS) refers to HIV after it has caused severe damage to the body’s organs and immune system, usually in the final stage. HIV targets and alters the immune system, while AIDS is a syndrome or range of symptoms that may develop in a person with poorly managed HIV. The pre-exposure prophylaxis of HIV is taking medicine to prevent getting HIV. Enhanced prophylaxis with ARV therapy is used to make advanced HIV responsive and lower patients’ fatality rate. This includes antimicrobial prophylaxis consisting of specific drugs such as cotrimoxazole, like in Akua’s case, and supplementary food.

Common Opportunistic Infections associated with HIV/AIDS and Treatment

When HIV/AIDS destroys the body’s immunity, certain opportunistic infections attack a person. These include pneumonia, tuberculosis(T.B.), salmonella infection, candidiasis, toxoplasmosis, and herpes simplex virus 1. These are prevented or treated by taking preventive drugs, vaccination, practising safe food preparation, being careful around animals to prevent animal-related infections, taking ARVs, and keeping a journal to record any new symptoms.

How should the Patient be Monitored and Managed?

After diagnosis, an HIV patient like Akua should be monitored, and her condition checked regularly. There are several ways to monitor HIV, and the most common is checking the CD4 count and viral load. Managing Akua’s situation requires a lifetime of ARV therapy, counselling, and discussing the importance of using safe contraception during sex as advised by her health physician.


The case of Akua is not uncommon. This follows exposure to regions where Hepatitis is considered endemic and the risk of contracting a virus, such as HIV in her case, after unprotected sex. The physical examination results, particularly her liver function tests, are a significant indicator of the diagnosis made. Also, the positive HIV test points to Hepatitis A as a risk factor for such patients. In addition, the HIV diagnosis brings about a detailed understanding of the virus from the CD4 count, viral load, and the three critical stages of the infection. Also, it helps us understand the risk factors, such as opportunistic infections like T.B., and the importance of managing the infection through ARV therapy and counselling.


McKnight, K.L. and Lemon, S.M., 2018. Hepatitis A virus genome organization and replication

strategy. Cold Spring Harbor perspectives in medicine, 8(12), p.a033480.


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