What is the incubation period of scarlet fever?

The disease develops quickly, and the early fever symptoms are easily ignored. The fever usually lasts for five days and is often mistaken for a cold. It has many stages and the body temperature can reach as high as 40°C. Generally, a large red rash will appear on the skin, and the throat may also be swollen and painful. Patients are often afraid of cold and afraid to speak. After entering the rash stage, the patient's body will have more and more rashes and the symptoms will become more and more obvious.

The incubation period is 2 to 5 days, but can be as short as 1 day or as long as 7 days.

1. Prodromal stage

Most of them suffer from sudden onset of chills and fever. In severe cases, the body temperature can rise to 39℃ ~ 40℃, accompanied by headache, sore throat, bayberry tongue, loss of appetite, general discomfort, nausea and vomiting. Infants may have delirium and seizures. The throat is red and swollen, and dots or flakes of secretions can be seen on the tonsils. The soft palate is congested and edematous, and may have rice-sized red macules or hemorrhagic spots, which is called intramucosal rash, which usually appears before the skin rash.

Rash is one of the most important symptoms of scarlet fever. Most cases appear within 1 to 2 days of onset. Occasionally, the rash may appear as late as the 5th day. It starts from behind the ears, the base of the neck and the upper chest, and spreads to the chest, back, upper limbs and finally the lower limbs within 1 day. In some cases, it takes several days to spread throughout the body.

The typical rash is characterized by dense and evenly distributed needle-cap-sized dot-like congested red rashes on the basis of redness and congestion on the skin all over the body. They all disappear when pressed by hand, but reappear after the pressure is removed. Occasionally, it appears as "chicken skin-like" papules. In severe cases of poisoning, there may be hemorrhagic rash, and patients often feel itchy. In skin folds such as the armpits, elbows, and groin, dense and linear rashes can be seen, which are called "Pa's lines." The face is red and flushed, with a small amount of rash. The area around the mouth and nose appears pale in comparison, which is called "perioral pale circle".

At the onset of the disease, the tongue is covered with white fur, and the papillae are red and swollen, protruding above the white fur, especially at the tip and edges of the tongue. After 2 to 3 days, the white coating begins to fall off, the tongue surface becomes smooth and flesh-red, and there may be superficial cracks, but the papillae are still protruding, which is called "bayberry tongue".

The rash usually reaches its peak within 48 hours and disappears completely in 2 to 4 days. Severe cases may last for 5 to 7 days or even longer. The submandibular and cervical lymph nodes may be enlarged and tender, and are generally non-suppurative. The body temperature is higher when the rash appears. When the rash spreads all over the body, the body temperature gradually drops, the symptoms of poisoning disappear, and the rash retreats.

Peeling begins within a week after the rash subsides, and the order of peeling areas is the same as the order of rash appearance. The trunk is mostly bran-like peeling, and large membranous peeling is often seen in the thick skin of the palms and soles. Fissured peeling at the nail ends is a typical manifestation. Peeling lasts for 2 to 4 weeks and leaves no pigmentation.