Question

A company held an elaborate holiday dinner party for its 42 employees. Within 3 to 4 weeks, many of the banquet attendees complained of experiencing fatigue, fever, nausea, and dark urine and were observed to be jaundiced. The group exhibited no bacterial infections in common. The employees who became ill had all eaten raw oysters at the party. The company doctor assayed a sample of the employees' blood for anti-hepatitis B antibodies, but all samples were negative for anti-hepatitis B surface antigen immunoglobulin M. The causative agent consistent with this history is most likely: A. hepatitis A virus. B. hepatitis B virus. C. hepatitis C virus. D. hepatitis D virus. E. hepatitis E virus.

Short answer

The most likely cause of the symptoms observed in the employees is Hepatitis A virus.

Step-by-step solution

Identify symptoms and mode of transmission

The symptoms listed (fatigue, fever, nausea, dark urine and jaundiced skin and eyes) along with the eating of raw oysters, are commonly associated with a form of Hepatitis that is fecal-oral transmitted. Hepatitis types A and E follow such a path.

Rule out hepatitis B

The company doctor tested for anti-hepatitis B antibodies- specifically, the anti-hepatitis B surface antigen (anti-HBsAg) immunoglobulin M (IgM), which would be present in acute hepatitis B infections, but did not find any. This rules out Hepatitis B as a likely cause.

Evaluate other possibilities

Hepatitis C and D are not usually associated with foodborne transmissions. Hepatitis A and E are both transmitted through contaminated food or water, however, Hepatitis E is rare in non-endemic areas and mostly associated with contaminated water and not shellfish. Therefore, Hepatitis A is the most likely causative agent in this scenario.

Key concepts

Symptoms of Hepatitis A

When discussing the symptoms of an infectious disease like hepatitis A, it's crucial to recognize them for early treatment and prevention of spread. Individuals infected with the hepatitis A virus (HAV) usually start showing symptoms 2 to 7 weeks after exposure. The illness typically begins abruptly with the sudden onset of fever, malaise, and a loss of appetite. Soon after, more specific symptoms such as nausea, abdominal discomfort, and the telltale sign of jaundice (a yellowing of the skin and eyes) appear. Dark urine and clay-colored stool are also associated markers of this condition.

Children under six years may exhibit fewer and milder symptoms, often going unnoticed, while older children and adults tend to have more pronounced and debilitating symptoms, which can be mistaken for a severe case of the flu. These symptoms usually improve within two months. Importantly, not every exposed individual will exhibit symptoms, but they can still spread the virus to others.

Transmission of Hepatitis A

Understanding how hepatitis A spreads is key to controlling outbreaks. The primary mode of transmission of the hepatitis A virus is via the fecal-oral route. This means it can happen when an uninfected person ingests food or water that has been contaminated with the feces of an infected person. This is often due to inadequate hand-washing or consuming food prepared by someone who is infected.

Common sources of HAV transmission include consumption of raw or undercooked shellfish from contaminated waters, eating food handled by someone who is infected, or drinking contaminated water. It is also possible to acquire hepatitis A through close personal contact with an infected person, such as caring for someone who is ill. Outbreaks are common in regions with poor sanitation or overcrowding, but individual cases can appear anywhere if hygiene practices are not followed. HAV is highly contagious and can survive in the environment for extended periods, which is why proper food handling and good personal hygiene habits, including hand washing, are essential for prevention.

Diagnosis of Hepatitis A

Diagnosing hepatitis A begins with a clinical assessment of the patient's history and a physical examination, with attention to signs such as jaundice. Laboratory testing is vital to confirm the diagnosis. Blood tests are used to check for the presence of specific antibodies against the HAV. The most commonly used test is the detection of IgM antibodies to hepatitis A virus (IgM anti-HAV), which are typically present in the blood of patients recently infected with HAV.

If the IgM anti-HAV test is positive, it indicates a recent infection—likely within the past 2 to 6 months—and is also a sign that the person is contagious. A test for IgG antibodies might be done which can indicate a past infection and lifelong immunity to the virus. In the context of an outbreak, public health officials may also investigate the source of the infection to prevent further cases. Patients who are diagnosed with hepatitis A should be monitored for clinical worsening and supportive care if needed, as no specific antiviral therapy is available for HAV infections.