What are the clinical features of measles?

Measles is generally an acute respiratory infectious disease caused by the measles virus. Its clinical features mainly include fever, upper respiratory catarrhal symptoms, measles mucosal spots, skin maculopapular rash, systemic toxic symptoms, and complications. The specific analysis is as follows:

1. Fever

Fever results from the stimulation of the hypothalamic thermoregulatory center due to viremia and the host's immune response. Fever usually correlates with the timing of the rash appearance and generally begins 2–4 days before the rash emerges. Fever is often the initial symptom of measles, typically presenting as persistent high-grade fever reaching 39–40°C, lasting for 3–4 days. The severity of fever usually increases progressively with disease progression.

2. Upper Respiratory Catarrhal Symptoms

Catarrhal symptoms peak during the rash stage and gradually subside after the rash fades. Pronounced upper respiratory tract inflammation occurs simultaneously with fever, including cough, rhinorrhea, sneezing, and pharyngeal congestion. Some patients may also experience conjunctival congestion, lacrimation, photophobia, and other signs of conjunctivitis.

3. Measles Mucosal Spots

These are specific early signs of measles, appearing 1–2 days before the rash. They are located on the buccal mucosa opposite the second molars, presenting as grayish-white spots approximately 1–3 mm in diameter, surrounded by a red halo. Initially, only a few spots may be present, but they rapidly increase in number and coalesce, potentially involving the entire buccal mucosa. These spots typically fade 1–2 days after the rash appears.

4. Skin Maculopapular Rash

The rash appears after 3–4 days of fever, starting behind the ears and at the hairline, gradually spreading to the forehead, face, neck, and then downward to the trunk and limbs, finally reaching the palms and soles. Initially, the rash presents as red maculopapules 2–5 mm in diameter, blanching on pressure, with normal-appearing skin between lesions. Subsequently, the lesions may merge into larger patches with increased pigmentation.

5. Systemic Toxic Symptoms and Complications

Systemic toxic symptoms such as lethargy, poor appetite, and fatigue may accompany the disease course. Severe cases can present with delirium and convulsions. Common complications include pneumonia, laryngitis, myocarditis, and encephalitis, which can worsen the condition or threaten life.

Measles is a serious disease that may lead to severe complications such as encephalitis, vision impairment, and even death. If symptoms of measles appear, immediate medical attention is recommended for treatment, and contact with others should be avoided to prevent viral transmission.