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Signs of the flu
Last reviewed: 04.07.2025
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The incubation period of influenza ranges from several hours to 2 days for influenza A and up to 3-4 days for influenza B. The disease begins acutely, with a rise in body temperature to high values (39-40 ° C), accompanied by chills, general weakness, fatigue, muscle and joint pain. The fever reaches its maximum by the end of the first, less often on the second day of the disease. By this time, all the signs of influenza are expressed to the maximum. Children complain of headaches, usually in the temples, forehead, superciliary arches, eyeballs; they lose their appetite, sleep worsens, nausea, vomiting are possible, and in severe cases - delirium and hallucinations. Catarrhal symptoms are usually weakly expressed and are represented by coughing, congestion and scanty mucous discharge from the nose, sore throat, especially when swallowing. In severe cases, nosebleeds, convulsions, short-term loss of consciousness, meningeal symptoms (stiff neck, weakly positive Kernig's sign) are possible.
On the 1st day of the disease, blood tests may show neutrophilic leukocytosis with a slight shift to the left; from the 2nd-3rd day, leukopenia, eosinophilia, and lymphocytosis are detected. ESR is normal, red blood counts are unchanged.
The course of influenza is acute. The duration of the febrile period is usually 3-5 days. After the body temperature decreases, the condition of children improves. The recurrence of fever is usually caused by the superposition of a bacterial infection or the development of another acute respiratory viral infection. The total duration of the disease (in the absence of complications) is usually 7-10 days. After the flu, post-infectious asthenia (increased fatigue, weakness, headache, irritability, insomnia) may persist for 2-3 weeks.
[ Influenza in newborns and children of the first year of life
The disease usually begins gradually with a slight rise in body temperature, symptoms of influenza intoxication are absent or mild. Newborns refuse to breastfeed, their body weight decreases. There may be mild catarrhal symptoms in the form of cough, nasal congestion, "snoring", and repeated vomiting is common. Croup syndrome in children of the first half of life rarely develops; segmental lung damage is uncharacteristic. Despite the mild initial clinical manifestations, the course of influenza in children of the first year of life is significantly more severe due to the frequent addition of a bacterial infection and the occurrence of purulent complications (otitis, pneumonia, etc.). Mortality is 3 times higher than in older children.
Features of "bird flu"
The disease caused by avian influenza viruses (H5N1, H7N7, etc.) is characterized by a severe course in both adults and children due to the development of primary viral (interstitial) pneumonia in the early stages, complicated by adult respiratory distress syndrome. Severe intoxication syndrome is associated with liver and kidney damage due to the pantropism of the virus; leukopenia and lymphopenia are observed. In the countries of Southeast Asia, where "bird flu" was first detected, the disease was fatal in 70% of cases.