Infection of the salivary glands, particularly the parotid glands, by a specific virus most commonly leads to which disease in humans?

Introduction / Context:
The salivary glands, especially the parotid glands near the ears, can be affected by infections that cause swelling and pain. One classic childhood viral illness targets these glands and is well known to public health authorities. This question tests whether you can correctly name the disease caused by viral infection of the salivary glands.

Given Data / Assumptions:

• The infection affects salivary glands, particularly the parotid glands.
• The cause is a virus, not a bacterium.
• Options include mumps, tetanus, pyorrhoea, ulcers, and diphtheria.
• We assume typical human infections in the context of school level biology.

Concept / Approach:
Mumps is an acute viral illness caused by the mumps virus, a paramyxovirus. It primarily infects the parotid salivary glands, leading to painful swelling on one or both sides of the face, fever, and difficulty in chewing or swallowing. Tetanus is caused by a bacterial toxin from Clostridium tetani and affects the nervous system, leading to muscle spasms, not specifically the salivary glands. Pyorrhoea refers to gum disease and periodontal infection. Ordinary mouth ulcers have various causes but are not specifically linked to a viral infection of the salivary glands. Diphtheria is a bacterial infection of the throat and upper respiratory tract. Therefore, the classic viral infection of salivary glands is mumps.

Step-by-Step Solution:
Step 1: Focus on the clue that salivary glands are infected by a virus. Step 2: Recall that mumps is known for causing painful swelling of the parotid glands near the jaw and ears. Step 3: Recognise that tetanus is associated with wound infection and muscle rigidity, not gland swelling. Step 4: Note that pyorrhoea affects the gums and supporting structures of the teeth, not the salivary glands. Step 5: Understand that simple ulcers and diphtheria involve the mouth and throat lining rather than the salivary glands specifically. Step 6: Conclude that the correct disease associated with viral infection of salivary glands is mumps.

Verification / Alternative check:
Medical references describe mumps as an infection that primarily targets the parotid glands and sometimes other glands like the testes and pancreas. Clinical features include parotid swelling, pain, fever, and malaise. In vaccination schedules, the MMR vaccine (measles, mumps, rubella) is given to prevent this viral illness. None of the other listed conditions are caused by a virus primarily attacking the salivary glands, which confirms mumps as the correct answer.

Why Other Options Are Wrong:
Tetanus: Caused by a bacterial toxin affecting nerves and muscles, not a viral salivary gland infection. Pyorrhoea: Refers to gum disease and pus formation around teeth, typically due to bacterial infection. Mouth ulcers: Localised lesions in the oral mucosa with varied causes; not specifically a salivary gland viral disease. Diphtheria: Bacterial infection of the throat and upper respiratory tract, not focused on salivary glands.

Common Pitfalls:
Students may confuse mumps with general mouth or throat conditions because they all involve the facial region. The key is to focus on which structure is primarily affected. If the salivary glands and particularly the parotid glands are swollen due to a virus, mumps is the classic diagnosis. Remembering the characteristic chipmunk face swelling helps reinforce this association.

Final Answer:
Viral infection of the salivary glands most commonly leads to mumps.