Scarlet fever is a common infectious disease caused by group A streptococcus. The bacteria infect the throat and release a toxin that leads to a rash all over the body. The incubation period for the infection is less than one week, and the rash usually breaks out on the second day.
The strep infection is spread by droplets during coughing and sneezing, and by direct contact with infected body fluids such as saliva. Most children with strep throat do not develop scarlet fever, as only certain types of group A strep bacteria make the toxin that causes the rash. Contrary to popular belief, the infection is not more serious because of the rash. In rare cases, scarlet fever can occur as a result of a skin infection, impetigo, caused by the same strep bacteria.
Scarlet fever is much more common in children than in adults, and it mostly affects five- to twelve-year-olds. Unlike many other childhood diseases, people can have scarlet fever several times in their life. About a quarter of all teenagers have already had scarlet fever at least once.
Scarlet Fever risk factors
Risk factors that increase the likelihood of developing scarlet fever include:
- Age – being between the ages of two and 10 years
- An untreated infection
- Exposure to a family or household member who has a streptococcal infection
- Crowded conditions, such as a daycare center or school, and
- Being prone to having Streptococcus bacteria living in your throat
Causes of Scarlet Fever
- Scarlet fever is caused by Streptococcus (group A strep) bacteria, which causes strep throat. When the bacteria release toxins in the body, the characteristic red rash results.
- The bacteria primarily spread when an infected person sneezes or coughs, and passes the bacteria through liquid droplets in their nose or mouth.
- Infected droplets on the surface of shared dishes and utensils may also cause transmission.
- Touching the open sores on the skin of a person with a streptococcal skin infection can also transmit the bacteria. Following exposure, it takes 2-4 days until the onset of symptoms.
Scarlet Fever symptoms
Scarlet fever usually is triggered by a strep throat infection, which causes the following symptoms:
- Fever and chills
- A red and sore throat
- Enlarged tonsils
- Swollen lymph nodes (“swollen glands”) in the neck
Within 12 to 48 hours after these symptoms appear, the typical scarlet fever rash begins.
The scarlet fever rash is as bright red as sunburn, and it often has a fine texture like sandpaper (“sandpaper rash”) or gooseflesh (goosebumps). It usually starts in the underarm area, groin, and neck, then spreads to the trunk, back, arms and legs. Other symptoms of scarlet fever include:
- A pale area around the mouth
- White strawberry tongue- A white coating with red dots on the tongue’s surface
- Red strawberry tongue or raspberry tongue that occurs when the white tongue coating peels and leaves a red coating with red dots
- Pastia’s lines- A darkening or redness of the normal skin creases, especially in the crook of the arm
Development of the strawberry tongue associated with scarlet fever
Occasionally, scarlet fever follows a streptococcal skin infection, such as an infection of burns or wounds, or impetigo. When this happens, the rash and related skin symptoms appear, but there are no symptoms related to strep throat.
Complications of scarlet fever
Most cases of scarlet fever don’t cause complications, particularly if the condition is properly treated.
In the early stages, there’s a small risk of:
- An ear infection
- A throat abscess (a painful collection of pus)
- Sinusitis (inflammation of the sinuses)
- Pneumonia (inflammation of the lungs)
Very rare complications that can occur at a later stage include:
- Rheumatic fever, which can cause joint pain, chest pain and shortness of breath
- Glomerulonephritis (damage to the tiny filters inside the kidneys)
- Liver damage
- Osteomyelitis (infection of the bone)
- Blood poisoning
- Necrotizing fasciitis (a flesh-eating disease)
- Toxic shock syndrome (a rare, life-threatening bacterial infection)
You may have one of these rare complications if you’re very unwell, in severe pain and have a severe headache, vomiting or diarrhea.
Diagnosis and test
It can be clinically diagnosed; further testing may be required to distinguish it from other illnesses.
Rapid antigen detection test- This is a very specific test but not very sensitive i.e., if the result is positive (indicating that the Group A Strep Antigen was detected) then it is appropriate to treat them with antibiotics. However, if the test is negative (indicating that they do not have Group A Strep Pharyngitis), then a throat culture is required to confirm since it could be a false negative result.
Throat cultures- This is done after antibiotic therapy and can tell you if the infection has been removed.
Treatment and medications
Most mild cases of scarlet fever go away in about a week without treatment. However, you are advised to get treatment as this will speed recovery. If it is left untreated, the skin may continue to shed for several weeks. There is also a higher risk of complications without treatment. Most people recover around four to five days after starting treatment.
- The most common treatment for scarlet fever is a 10-day course of antibiotics. This will usually be penicillin taken by mouth. For those allergic to penicillin, the antibiotic erythromycin can be used instead
- Stay at home for at least 24 hours after starting treatment
- Symptoms usually go in a few days if the antibiotics are taken properly. The whole course of treatment must be finished to make sure the infection is fully cleared
- The fever will normally disappear within 12 to 24 hours of starting antibiotics
- If you have scarlet fever, drink plenty of cool fluids, especially if you do not have much of an appetite. Keep the room cool.
- Paracetamol can also be taken to relieve aches and pains and bring down a high temperature. Calamine lotion can relieve the itch of the rash.
How it can be prevented
You can prevent the spread of scarlet fever and ‘strep throat’ by following this advice:
- Cover your mouth and nose with a tissue when you cough or sneeze
- Throw tissues in the bin after you use them
- Wash your hands often with soap and water, especially after you cough or sneeze. Alcohol-based hand cleaners are also effective
- Wash your hands before preparing food
- See your doctor if you or your child has symptoms of sore throat and fever