Key messages

  • Group A streptococci (GAS) causes a variety of infections, from relatively mild throat and skin infections, to fevers and severe invasive diseases.
  • School and childcare exclusions do apply.
  • People with chronic illnesses such as cancer and diabetes, those on kidney dialysis, and those who use medications such as steroids have a higher risk of infection than other people.
  • Many GAS infections are treated with antibiotics.

Notification requirement for streptococcal disease

Notification is not required.

Primary school and children’s services centres exclusion for streptococcal disease

Exclude until the child has received antibiotic treatment for at least 24 hours and feels well.

Infectious agent of streptococcal disease

Streptococcus pyogenes, otherwise known as Group A streptococci (GAS), has more than 130 serologically distinct types. Those producing skin infections are usually of different serological types from those that cause pharyngitis and tonsilitis.

Identification of streptococcal disease

Clinical features

The spectrum of disease caused by GAS includes:

  • nasopharyngeal infections, including pharyngitis and tonsillitis
  • skin infections such as cellulitis, impetigo and pyoderma
  • scarlet and puerperal fever
  • severe invasive disease such as necrotising fasciitis, toxic shock syndrome and septicaemia.

Post-streptococcal immunological sequelae include acute rheumatic fever and acute glomerulonephritis.

Diagnosis

Superficial infection is diagnosed by isolation of the organism from infected tissues. Invasive infection can be confirmed by isolation of the organism from a normally sterile site, such as blood. Throat swabs frequently identify inapparent nonpathogenic streptococcal carriage. Definitive identification depends on specific serogrouping procedures.

Antigen detection tests have been used in the United States and elsewhere for rapid identification. A rise in serum antibody titres (anti-streptolysin O, anti-hyaluronidase, anti-DNAase B) may also be demonstrated in sera taken in the acute and convalescent phases of the disease.

Incubation period of Streptococcus

The incubation period is usually 1–4 days.

Public health significance and occurrence of streptococcal disease

The incidence of GAS infections and their sequelae is not well documented in Australia except in Aboriginal communities in northern Australia. In the United States, acute pharyngitis is one of the most common reasons for seeking medical advice. GAS is thought to be responsible for 37 per cent of pharyngitis in children and 5–15 per cent in adults.

Data from a voluntary surveillance system conducted in Victoria in 2002–04 found the incidence of invasive GAS disease to be 2.7 per 100,000 per year, with a case-fatality rate of 7.8 per cent.

Outbreaks occur in childcare settings, in institutions, and in remote communities in northern and central Australia.

Reservoir for Streptococcus

Humans are the reservoir.

Mode of transmission of Streptococcus

GAS is usually transmitted via large respiratory droplets or direct contact with infected people or carriers. It is rarely transmitted by indirect contact through objects. Rare outbreaks of streptococcal infection may occur as a result of ingestion of contaminated foods, such as milk, milk products and eggs.

Period of communicability of streptococcal disease

With appropriate antibiotic therapy, GAS is communicable for 24–48 hours. In untreated uncomplicated cases, communicability can last for 10–21 days. Communicability can be prolonged in untreated complicated cases.

Susceptibility and resistance to streptococcal disease

Pharyngitis and tonsillitis are common in children aged 5–15 years, whereas pyoderma occurs more frequently in children aged less than 5 years. Most people in their lifetime will develop a GAS throat or skin infection, and many of the throat infections may be subclinical. People with chronic illnesses such as cancer and diabetes, those on kidney dialysis, and those who use medications such as steroids have a higher risk than healthy people. There is an increased risk of infection in varicella (chickenpox).

Control measures for streptococcal disease

Preventive measures

There are currently no vaccines available. Foodborne disease can be prevented by pasteurising milk and milk products, and careful preparation and storage of high-risk foods, particularly eggs.

Control of case

Treatment is dependent on the clinical presentation and severity of disease. Evidence has accumulated that antibiotics may not always be indicated in pharyngitis or tonsillitis. The current version of Therapeutic guidelines: antibiotic should be consulted before treatment.

Infected children should be excluded from schools and children’s services centres until they have received antibiotics for at least 24 hours and feel well. People with skin lesions should be excluded from food handling until infection has resolved.

Control of contacts

Consider the diagnosis in symptomatic contacts. Few people who come in contact with GAS will develop invasive GAS disease. At present, the role of antibiotic prophylaxis for close contacts of cases of invasive GAS infection is not established. However, in certain circumstances, antibiotic therapy may be appropriate for those at higher risk of infection.

Control of environment

Standard infection control procedures should be applied.

Outbreak measures for streptococcal disease

Outbreak management is dependent on the setting and specific disease. Seek advice from the department.

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