A 23-year-old woman presents with vulvar ulcers and lymphadenopathy. Testing confirms primary HSV infection. Which of the following statements about HSV antibody development is correct?
Q2
A 35-year-old male anesthesiologist presents to the occupational health clinic after a needlestick exposure while obtaining an arterial line in a patient with cirrhosis. In addition to a standard bloodborne pathogen laboratory panel sent for all needlestick exposures at his hospital, additional hepatitis panels are ordered upon the patient's request. The patient's results are shown below:
HIV 4th generation Ag/Ab: Negative/Negative
Hepatitis B surface antigen (HBsAg): Negative
Hepatitis C antibody: Negative
Anti-hepatitis B surface antibody (HBsAb): Positive
Anti-hepatitis B core IgM antibody (HBc IgM): Negative
Anti-hepatitis B core IgG antibody (HBc IgG): Positive
What is the most likely explanation of the results above?
Q3
A 28-year-old man presents to the office with complaints of malaise, anorexia, and vomiting for the past 2 weeks. He also says that his urine is dark. The past medical history is unremarkable. The temperature is 36.8°C (98.2°F), the pulse is 72/min, the blood pressure is 118/63 mm Hg, and the respiratory rate is 15/min. The physical examination reveals a slightly enlarged, tender liver. No edema or spider angiomata are noted. Laboratory testing showed the following:
HBsAg Positive
IgM anti-HBc < 1:1,000
Anti-HBs Negative
HBeAg Positive
Anti-HBe Negative
HBV DNA 2.65 × 10⁹ IU/L
Alpha-fetoprotein 125 ng/mL
What is the most likely cause of this patient's condition?
Q4
A 26-year-old woman who is a medical student is undergoing evaluation after sticking herself with a needle while drawing blood from a patient. The patient’s medical history is unknown. A blood sample from the medical student is drawn and processed, and the results are presented below:
Anti-HAV IgM negative
Anti-HAV IgG positive
HBsAg negative
HBeAg negative
Anti-HBs negative
Anti-HBc IgG negative
Anti-HBc IgM negative
Anti-HBe negative
Anti-HCV negative
What is true about the student’s laboratory findings?
Q5
A 25-year-old man presents to the office for a 3-day history of fever and fatigue. Upon further questioning, he says that he also had constant muscular pain, headaches, and fever during these days. He adds additional information by giving a history of regular unprotected sexual relationship with multiple partners. He is a non-smoker and drinks alcohol occasionally. The heart rate is 102/min, respiratory rate is 18/min, temperature is 38.0°C (100.4°F), and blood pressure is 120/80 mm Hg. On physical examination, he is icteric and hepatosplenomegaly is evident with diffuse muscular and abdominal tenderness particularly in the right upper quadrant. The serologic markers show the following pattern:
Anti-HAV IgM negative
HBsAg positive
Anti-HBs negative
IgM anti-HBc positive
Anti-HCV negative
Anti-HDV negative
What is the most likely diagnosis?
Q6
A 52-year-old male patient with chronic alcoholism presents to an ambulatory medical clinic, where the hepatologist elects to perform comprehensive hepatitis B screening, in addition to several other screening and preventative measures. Given the following choices, which serologic marker, if positive, would indicate the patient’s immunity to the hepatitis B virus?
Q7
A 33-year-old female comes to her primary care physician with complaints of fatigue and nausea. She has also noticed that her skin tone is darker than it used to be. On exam, the physician notes that the woman appears to be jaundiced and obtains liver enzymes which demonstrate an elevated AST and ALT. Further testing subsequently confirms the diagnosis of hepatitis B (HBV). The woman is extremely concerned about transmitting this disease to her loved ones and ask how HBV is transmitted. By which of the following routes can HBV be spread? (I) blood, (II) sexual contact, (III) maternal-fetal, and/or (IV) breast milk?
Q8
A 35-year-old man with no known past medical history presents to his physician because he is applying for a job as a healthcare worker, which requires screening for the hepatitis B virus (HBV). The patient states that he is in good health and denies any symptoms. His vital signs and physical exam are unremarkable. Labs are drawn, and the patient's HBV serology shows the following:
HBsAg: positive
anti-HBsAg antibody: negative
anti-HBcAg IgM: negative
anti-HBcAg IgG: positive
HBeAg: negative
anti-HBeAg antibody: positive
Which of the following best describes this patient's results?
Q9
Two viruses, X and Y, infect the same cell and begin to reproduce within the cell. As a result of the co-infection, some viruses are produced where the genome of Y is surrounded by the nucleocapsid of X and vice versa with the genome of X and nucleocapsid of Y. When the virus containing genome X surrounded by the nucleocapsid of Y infects another cell, what is the most likely outcome?
Q10
A group of researchers conducted various studies on hepatitis C incidence and prevalence. They noticed that there is a high prevalence of hepatitis C in third-world countries, where it has a significant impact on the quality of life of the infected individual. The research group made several attempts to produce a vaccine that prevents hepatitis C infection but all attempts failed. Which of the following would most likely be the reason for the failure to produce a vaccine?
HBV serological markers US Medical PG Practice Questions and MCQs
Question 1: A 23-year-old woman presents with vulvar ulcers and lymphadenopathy. Testing confirms primary HSV infection. Which of the following statements about HSV antibody development is correct?
A. IgG appears immediately after infection
B. IgG antibodies appear 2-3 weeks after infection and persist (Correct Answer)
C. No antibody response occurs
D. IgM and IgG appear simultaneously at 6 weeks
Explanation: ***IgG antibodies appear 2-3 weeks after infection and persist***
- Following primary HSV infection, the body mounts an immune response, with **IgG antibodies** typically becoming detectable approximately **2-3 weeks post-infection**. [1]
- These **IgG antibodies** persist for life, providing long-term immunity and serving as a marker of past or latent infection. [1]
*IgG appears immediately after infection*
- The immune system requires time to generate a robust antibody response, so **IgG antibodies** do not appear immediately following infection. [2]
- The initial immune response involves innate immunity and the production of **IgM antibodies** before IgG. [1], [2]
*No antibody response occurs*
- The body's immune system recognizes the viral antigens and mounts an antibody response to combat the infection.
- Absence of an antibody response would imply a complete failure of the adaptive immune system, which is not the case in immunocompetent individuals with primary HSV. [1]
*IgM and IgG appear simultaneously at 6 weeks*
- **IgM antibodies** are produced earlier in the immune response compared to **IgG**. [2]
- While both may be present at 6 weeks, their appearance is not simultaneous, with IgM preceding IgG, and IgG often detectable by 2-3 weeks, not waiting until 6 weeks. [1]
Question 2: A 35-year-old male anesthesiologist presents to the occupational health clinic after a needlestick exposure while obtaining an arterial line in a patient with cirrhosis. In addition to a standard bloodborne pathogen laboratory panel sent for all needlestick exposures at his hospital, additional hepatitis panels are ordered upon the patient's request. The patient's results are shown below:
HIV 4th generation Ag/Ab: Negative/Negative
Hepatitis B surface antigen (HBsAg): Negative
Hepatitis C antibody: Negative
Anti-hepatitis B surface antibody (HBsAb): Positive
Anti-hepatitis B core IgM antibody (HBc IgM): Negative
Anti-hepatitis B core IgG antibody (HBc IgG): Positive
What is the most likely explanation of the results above?
A. Window period
B. Chronic infection
C. Acute infection
D. Immune due to infection (Correct Answer)
E. Immune due to vaccination
Explanation: ***Immune due to infection***
- The presence of **anti-HBc IgG** along with **anti-HBsAb** in the absence of **HBsAg** indicates past resolution of HBV infection.
- This combination confers **natural immunity** following a prior exposure, distinguishing it from vaccine-induced immunity (which would lack anti-HBc IgG).
*Window period*
- This period is characterized by the absence of **HBsAg** and **anti-HBsAb**, with the only positive marker being **anti-HBc IgM**.
- The patient's results show positive **anti-HBsAb** and **anti-HBc IgG**, which rule out a window period.
*Chronic infection*
- Chronic infection is defined by the persistence of **HBsAg** for more than six months.
- The patient's **HBsAg is negative**, therefore excluding chronic infection.
*Acute infection*
- Acute infection would be evidenced by the presence of **HBsAg** and often **anti-HBc IgM**.
- Both **HBsAg** and **anti-HBc IgM** are negative in this patient, ruling out acute infection.
*Immune due to vaccination*
- Vaccination leads to the development of **anti-HBsAb** but does not produce **anti-HBc antibodies**.
- The presence of **anti-HBc IgG** in this patient indicates exposure to the complete virus, not just vaccination.
Question 3: A 28-year-old man presents to the office with complaints of malaise, anorexia, and vomiting for the past 2 weeks. He also says that his urine is dark. The past medical history is unremarkable. The temperature is 36.8°C (98.2°F), the pulse is 72/min, the blood pressure is 118/63 mm Hg, and the respiratory rate is 15/min. The physical examination reveals a slightly enlarged, tender liver. No edema or spider angiomata are noted. Laboratory testing showed the following:
HBsAg Positive
IgM anti-HBc < 1:1,000
Anti-HBs Negative
HBeAg Positive
Anti-HBe Negative
HBV DNA 2.65 × 10⁹ IU/L
Alpha-fetoprotein 125 ng/mL
What is the most likely cause of this patient's condition?
A. Acute HBV infection
B. Passive immunity
C. Acute resolving infection
D. Resolved HBV infection (innate immunity)
E. Acute exacerbation of chronic HBV infection (Correct Answer)
Explanation: ***Acute exacerbation of chronic HBV infection***
- The combination of **HBsAg positive** (indicating extant infection) and **IgM anti-HBc < 1:1,000** (a low titer consistent with chronic infection, not acute) points towards a pre-existing chronic hepatitis B infection.
- The elevated **HBV DNA (2.65 × 109 IU/L)**, along with clinical symptoms like malaise, anorexia, vomiting, dark urine, and a tender liver, suggests an **acute exacerbation** of this chronic condition.
*Acute HBV infection*
- An acute HBV infection would typically present with a **high titer of IgM anti-HBc** and often **HBeAg positive** initially, but this patient's low IgM anti-HBc titer rules out a new acute infection.
- While symptoms align with acute hepatitis, the serology (low IgM anti-HBc) is not characteristic of primary acute infection.
*Passive immunity*
- Passive immunity would be characterized by the presence of **Anti-HBs without HBsAg**, which is not seen here.
- This scenario usually occurs after receiving hepatitis B immunoglobulin or transplacental transfer of antibodies.
*Acute resolving infection*
- A resolving acute infection would typically show a **decrease in HBsAg** and the **presence of Anti-HBs**, neither of which are observed in this patient.
- The **high viral load (HBV DNA)** and persistent HBsAg also contradict a resolving infection.
*Resolved HBV infection (innate immunity)*
- A resolved HBV infection is defined by the **absence of HBsAg** and the **presence of Anti-HBs**, along with anti-HBc.
- This patient still has **HBsAg present** and **Anti-HBs negative**, ruling out a resolved infection.
Question 4: A 26-year-old woman who is a medical student is undergoing evaluation after sticking herself with a needle while drawing blood from a patient. The patient’s medical history is unknown. A blood sample from the medical student is drawn and processed, and the results are presented below:
Anti-HAV IgM negative
Anti-HAV IgG positive
HBsAg negative
HBeAg negative
Anti-HBs negative
Anti-HBc IgG negative
Anti-HBc IgM negative
Anti-HBe negative
Anti-HCV negative
What is true about the student’s laboratory findings?
A. She has not been vaccinated against the hepatitis B virus. (Correct Answer)
B. She recovered from a hepatitis B virus infection.
C. She is infected with the hepatitis D virus.
D. She can transmit the hepatitis A virus.
E. She is an asymptomatic carrier of the hepatitis B virus.
Explanation: ***She has not been vaccinated against the hepatitis B virus.***
- A **negative Anti-HBs** indicates a lack of protective antibodies developed either through vaccination or past infection.
- A **negative Anti-HBc IgG** and **IgM** further confirms no prior exposure to the hepatitis B core antigen, which would be present with natural infection.
*She recovered from a hepatitis B virus infection.*
- Recovery from HBV infection would typically show **positive Anti-HBs** and **positive Anti-HBc IgG**, neither of which are present here.
- The absence of **Anti-HBc antibodies** rules out past natural infection, whether resolved or chronic.
*She is infected with the hepatitis D virus.*
- Hepatitis D virus (HDV) infection only occurs in the presence of an active **Hepatitis B virus (HBV) infection**.
- The student's **HBsAg negative** status indicates no active HBV infection, thereby ruling out HDV.
*She can transmit the hepatitis A virus.*
- **Anti-HAV IgG positive** indicates prior exposure to HAV or vaccination, leading to immunity.
- **Anti-HAV IgM negative** suggests no acute HAV infection, meaning she is not currently infectious.
*She is an asymptomatic carrier of the hepatitis B virus.*
- An asymptomatic carrier of HBV would have **positive HBsAg** and likely **positive Anti-HBc IgG**, but both are negative in this case.
- The absence of **HBsAg** definitively rules out an active carrier state.
Question 5: A 25-year-old man presents to the office for a 3-day history of fever and fatigue. Upon further questioning, he says that he also had constant muscular pain, headaches, and fever during these days. He adds additional information by giving a history of regular unprotected sexual relationship with multiple partners. He is a non-smoker and drinks alcohol occasionally. The heart rate is 102/min, respiratory rate is 18/min, temperature is 38.0°C (100.4°F), and blood pressure is 120/80 mm Hg. On physical examination, he is icteric and hepatosplenomegaly is evident with diffuse muscular and abdominal tenderness particularly in the right upper quadrant. The serologic markers show the following pattern:
Anti-HAV IgM negative
HBsAg positive
Anti-HBs negative
IgM anti-HBc positive
Anti-HCV negative
Anti-HDV negative
What is the most likely diagnosis?
A. Viral hepatitis D
B. Viral hepatitis C
C. Viral hepatitis A
D. Viral hepatitis E
E. Viral hepatitis B (Correct Answer)
Explanation: ***Viral hepatitis B***
- The combination of **HBsAg positive** and **IgM anti-HBc positive** indicates an **acute hepatitis B infection**.
- Symptoms like **fever**, **fatigue**, **muscular pain**, **icterus**, and **hepatosplenomegaly** are consistent with acute viral hepatitis.
*Viral hepatitis D*
- This is ruled out by the **negative Anti-HDV** marker, as hepatitis D requires co-infection with hepatitis B.
- While patients can be co-infected with HBV and HDV, the serology explicitly excludes HDV in this case.
*Viral hepatitis C*
- This is excluded by the **negative Anti-HCV** marker, which would be positive in hepatitis C infection.
- Though sexually transmitted, the serological markers point away from HCV.
*Viral hepatitis A*
- This is ruled out by the **negative Anti-HAV IgM** marker.
- Hepatitis A is typically transmitted via the **fecal-oral route**, which is less consistent with the patient's sexual history.
*Viral hepatitis E*
- While hepatitis E can cause acute hepatitis, it is typically diagnosed by **IgM anti-HEV** antibodies, which are not provided as positive here.
- Transmission is usually **fecal-oral**, which is not the primary risk factor suggested by the patient's history.
Question 6: A 52-year-old male patient with chronic alcoholism presents to an ambulatory medical clinic, where the hepatologist elects to perform comprehensive hepatitis B screening, in addition to several other screening and preventative measures. Given the following choices, which serologic marker, if positive, would indicate the patient’s immunity to the hepatitis B virus?
A. HBeAb
B. HBeAg
C. HBsAb (Correct Answer)
D. HBsAg
E. HBcAb
Explanation: ***HBsAb***
- A positive **HBsAb** (Hepatitis B surface antibody) indicates immunity to hepatitis B virus, either from successful **vaccination** or **recovery from past infection**.
- This antibody provides **protective immunity** against future HBV infection and is the definitive marker of immunity.
*HBeAb*
- **HBeAb** (Hepatitis B e antibody) indicates **seroconversion** from HBeAg during chronic HBV infection, suggesting lower viral replication.
- It does **not confer immunity** against the virus itself and only reflects a phase of chronic infection.
*HBeAg*
- **HBeAg** (Hepatitis B e antigen) indicates **active viral replication** with high infectivity during ongoing hepatitis B infection.
- Its presence signifies a **replicative phase** of infection and increased risk of transmission to others.
*HBsAg*
- **HBsAg** (Hepatitis B surface antigen) indicates **active hepatitis B infection**, whether acute or chronic.
- This antigen is the **first serologic marker** to appear following exposure and confirms presence of the virus.
*HBcAb*
- **HBcAb** (Hepatitis B core antibody) indicates **previous or current exposure** to hepatitis B virus.
- It does **not differentiate** between acute, chronic, or resolved infection and does not confer protective immunity.
Question 7: A 33-year-old female comes to her primary care physician with complaints of fatigue and nausea. She has also noticed that her skin tone is darker than it used to be. On exam, the physician notes that the woman appears to be jaundiced and obtains liver enzymes which demonstrate an elevated AST and ALT. Further testing subsequently confirms the diagnosis of hepatitis B (HBV). The woman is extremely concerned about transmitting this disease to her loved ones and ask how HBV is transmitted. By which of the following routes can HBV be spread? (I) blood, (II) sexual contact, (III) maternal-fetal, and/or (IV) breast milk?
A. II, III
B. I, II, III, IV
C. I, II, III (Correct Answer)
D. I, III, IV
E. I only
Explanation: ***I, II, III***
- **Hepatitis B virus (HBV)** is primarily transmitted through contact with infected **blood** or other bloody body fluids (e.g., semen, vaginal secretions), making routes I (blood) and II (sexual contact) major modes of transmission.
- **Maternal-fetal transmission** (route III) can occur during childbirth, especially if the mother has high viral loads, although *in utero* transmission is rare.
*II, III*
- This option is incorrect because it omits **blood transmission (I)**, which is a major route for HBV spread through shared needles, transfusions, or open wounds.
- While sexual and maternal-fetal transmissions are significant, they do not account for all primary modes of spread.
*I, II, III, IV*
- This option is incorrect because while routes I, II, and III are valid, **breast milk (IV)** is generally *not* considered a significant route for HBV transmission.
- Studies have shown a very low, if any, risk of HBV transmission through breast milk, and breastfeeding is typically safe for HBV-positive mothers, especially if the infant is vaccinated.
*I, III, IV*
- This option is incorrect because it includes **breast milk (IV)**, which is not a clinically significant route of transmission, and it excludes **sexual contact (II)**, a very common mode of HBV spread.
- Many HBV infections are acquired through unprotected sexual intercourse with an infected partner.
*I only*
- This option is incorrect as it severely underrepresents the various transmission routes of HBV, omitting **sexual contact (II)** and **maternal-fetal transmission (III)**.
- While blood transmission is critical, HBV is also frequently spread through other bodily fluids and from mother to child.
Question 8: A 35-year-old man with no known past medical history presents to his physician because he is applying for a job as a healthcare worker, which requires screening for the hepatitis B virus (HBV). The patient states that he is in good health and denies any symptoms. His vital signs and physical exam are unremarkable. Labs are drawn, and the patient's HBV serology shows the following:
HBsAg: positive
anti-HBsAg antibody: negative
anti-HBcAg IgM: negative
anti-HBcAg IgG: positive
HBeAg: negative
anti-HBeAg antibody: positive
Which of the following best describes this patient's results?
A. Immune due to previous infection
B. Chronically infected, low infectivity (Correct Answer)
C. Immune due to previous vaccination
D. Acutely infected
E. Chronically infected, high infectivity
Explanation: ***Chronically infected, low infectivity***
- The presence of **HBsAg positive** for more than 6 months indicates **chronic HBV infection**. The presence of **anti-HBeAg antibody** and **negative HBeAg** suggests **low viral replication activity** and thus low infectivity.
- **HBeAg negativity** along with positivity for **HBV DNA** (if tested, though not provided here) would further differentiate this state as **"HBeAg-negative chronic hepatitis B,"** which typically implies lower, but still present, infectivity compared to HBeAg-positive chronic infection.
*Immune due to previous infection*
- Immunity due to previous infection is characterized by **negative HBsAg** and **positive anti-HBsAg antibody**, along with **positive anti-HBcAg IgG**.
- This patient, however, is **HBsAg positive** and **anti-HBsAg antibody negative**, ruling out resolved infection.
*Immune due to previous vaccination*
- Immunity due to vaccination is characterized by **negative HBsAg**, **positive anti-HBsAg antibody**, and **negative anti-HBcAg antibody** (both IgM and IgG).
- This patient has **positive HBsAg** and **positive anti-HBcAg IgG**, indicating either current or past infection, not vaccination-induced immunity.
*Acutely infected*
- **Acute infection** is characterized by **positive HBsAg**, **negative anti-HBsAg antibody**, and typically **positive anti-HBcAg IgM**.
- This patient has **negative anti-HBcAg IgM**, which makes acute infection unlikely, as IgM antibodies are present early in acute infection.
*Chronically infected, high infectivity*
- **High infectivity** in chronic HBV infection is typically indicated by **positive HBsAg** and **positive HBeAg**, often with high levels of HBV DNA.
- This patient is **HBeAg negative** and **anti-HBeAg antibody positive**, indicating a lower level of viral replication and thus lower infectivity.
Question 9: Two viruses, X and Y, infect the same cell and begin to reproduce within the cell. As a result of the co-infection, some viruses are produced where the genome of Y is surrounded by the nucleocapsid of X and vice versa with the genome of X and nucleocapsid of Y. When the virus containing genome X surrounded by the nucleocapsid of Y infects another cell, what is the most likely outcome?
A. Virions containing genome Y and nucleocapsid Y will be produced
B. No virions will be produced
C. Virions containing genome X and nucleocapsid Y will be produced
D. Virions containing genome Y and nucleocapsid X will be produced
E. Virions containing genome X and nucleocapsid X will be produced (Correct Answer)
Explanation: ***Virions containing genome X and nucleocapsid X will be produced***
- The virus containing **genome X** surrounded by **nucleocapsid Y** is a pseudotype. During the infection of a new cell, the **genome X** will direct the synthesis of new viral components, including **nucleocapsid X**.
- Since the genetic material (genome X) dictates the production of viral proteins, the new virions will be genetically identical to virus X, thus containing its own genome and nucleocapsid.
*Virions containing genome Y and nucleocapsid Y will be produced*
- This is incorrect because the infecting particle carried **genome X**, not genome Y.
- The genetic information encoded in the genome determines the type of progeny viruses produced.
*No virions will be produced*
- This is unlikely as the pseudotyped virus is capable of infection and delivery of a functional genome into the host cell.
- The cell is presumed to be permissive for virus replication.
*Virions containing genome X and nucleocapsid Y will be produced*
- This would only happen if the **nucleocapsid Y** was somehow replicated independently of its original genome, which is not how viral replication works.
- The progeny nucleocapsids are always encoded by the genome that is replicating within the cell.
*Virions containing genome Y and nucleocapsid X will be produced*
- This is incorrect. The infecting virus introduced **genome X** into the cell, not genome Y.
- The genetic material delivered determines the type of viral particles that will be synthesized.
Question 10: A group of researchers conducted various studies on hepatitis C incidence and prevalence. They noticed that there is a high prevalence of hepatitis C in third-world countries, where it has a significant impact on the quality of life of the infected individual. The research group made several attempts to produce a vaccine that prevents hepatitis C infection but all attempts failed. Which of the following would most likely be the reason for the failure to produce a vaccine?
A. Non-DNA genome
B. Tolerance
C. Antigenic mimicry
D. Polysaccharide envelope
E. Antigenic variation (Correct Answer)
Explanation: ***Antigenic variation***
- The **hepatitis C virus (HCV)** undergoes rapid **antigenic variation**, particularly in its envelope glycoproteins, which allows it to evade the host immune system.
- This high mutation rate presents a significant challenge for vaccine development, as a vaccine designed against one viral strain may not be effective against others.
*Non-DNA genome*
- While HCV is an **RNA virus** (non-DNA genome), this characteristic alone does not inherently prevent vaccine development; many effective RNA virus vaccines exist (e.g., measles, mumps).
- The type of genome is less critical than its stability and the virus's ability to mutate rapidly.
*Tolerance*
- **Immune tolerance** occurs when the immune system fails to respond to an antigen, often due to chronic exposure. While relevant in chronic HCV infection, it's not the primary reason for vaccine failure.
- The goal of a vaccine is to induce an effective immune response before tolerance can set in.
*Antigenic mimicry*
- **Antigenic mimicry** involves a pathogen's antigens resembling host antigens, potentially leading to autoimmune responses or immune evasion.
- While it can be a factor in some chronic infections, the rapid, diverse changes in HCV's surface antigens are a more prominent obstacle to vaccine design.
*Polysaccharide envelope*
- HCV is an **enveloped virus**, but its envelope is composed of **lipoproteins** with viral glycoproteins, not a polysaccharide capsule.
- Polysaccharide capsules are a feature of some bacteria (e.g., Streptococcus pneumoniae) and fungi, and while they can pose vaccine challenges, they are not relevant to HCV.
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