Diagnosis of rubella

Clinical picture by periods

The clinical diagnostic algorithm is based on the sequential progression of three periods of the disease:

1. Initial (catarrhal) period: prodromal symptoms are often mild or absent entirely. The patient may experience mild fever, myalgia, arthralgia, and headache. Catarrhal manifestations include mild rhinitis, conjunctivitis, lacrimation, photophobia (scleritis), and less commonly, a dry cough. The main marker of this stage is enlargement and tenderness of the cervical and occipital lymph nodes.
2. Rash period (peak of the disease): against the background of persisting lymphadenopathy, enanthema and exanthema appear. The rash (fine-macular rash) develops on unchanged skin, often starting on the face. Importantly, with the appearance of the rash, the intoxication syndrome and catarrhal manifestations do not tend to worsen.
3. Convalescence period: temperature and general well-being return to normal. The rash fades completely, strictly without desquamation or pigmentation.

Laboratory criteria

Laboratory tests are used for objective confirmation of the diagnosis.

• Complete blood count: a decrease in leukocyte count (leukopenia) and neutrophil count (neutropenia) against the background of lymphomonocytosis is characteristic. In some cases, plasma cells are detected. The ESR remains within normal limits. An entirely normal hemogram (normogram) is also acceptable.
• Serological method: ELISA and IFA are the primary tools. A diagnosis of acute infection is confirmed by detecting specific IgM class antibodies, which begin to be detected from days 3–4 of the illness.
• Avidity assessment: if IgM and IgG are detected simultaneously in the first serum sample (or IgG alone), the avidity of class G antibodies must be tested. If the avidity index is less than 30, this indicates the presence of "early" low-avidity antibodies, which reliably points to a recently onset, acute infection.

Differential diagnosis

The clinical picture of rubella should be differentiated from ARVI (influenza, parainfluenza, adenovirus, and RSV infection), measles, scarlet fever, and toxic-allergic reactions.

Special attention should be paid to differentiation from roseola infantum (sudden exanthema), caused by human herpesvirus type 6.

• In roseola, the febrile period is accompanied by a sudden spike in temperature up to 39.0–40.0°C.
• After 3–5 days, a sharp (critical) drop in temperature occurs, and it is precisely at this moment or a couple of hours later that an abundant polymorphic rash appears.
• The localization also differs: the roseolous rash starts on the back and torso, spreading to the abdomen and extremities, and is practically absent on the face.

A similar picture can also be caused by parvovirus infection. It is confirmed by detecting specific IgM (or isolating the virus itself) during the acute phase, or by high titers of IgG in a previously contracted disease.

Diagnosis formulation and management tactics

A detailed clinical diagnosis should include the form (typical/atypical), severity of the course, and the presence of complications (e.g., polyarthritis or meningoencephalitis).

Organization of treatment:

• Outpatient: the majority of patients with an uncomplicated form are managed this way. Symptomatic therapy is prescribed: bed rest, vitamins, antihistamines. If joint syndrome (arthritis) develops, nonsteroidal anti-inflammatory drugs (NSAIDs) are indicated.
• Hospitalization: is required for severe courses or the addition of CNS complications (encephalitis). Patients with neurological symptoms (seizure activity, sopor, focal signs) are treated in an ICU setting, using detoxicating, dehydrating therapy, and, if necessary, anticonvulsant and glucocorticosteroid therapy. Patients with a high risk of epidemic spread (living in dormitories or cramped conditions) are also referred to the hospital.

Discharge is permitted only after clinical recovery has occurred, but no earlier than the 7th day from the moment the exanthema appeared.

Briefly: answers to topical questions

What else to study on this topic

• Features of differential diagnosis between rubella and measles
• Pathogenesis of joint syndrome development in rubella
• Management tactics for pregnant women with suspected rubella virus infection
• Mechanisms of rubella encephalitis development

Other topics in the "Respiratory Infections" section

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