Update on Invasive Group A Streptococcus Infections

From the office of the Medical Health Officer.

Recent Epidemiology: Recent reports of invasive Group A streptococcal (iGAS) infection in Fraser South (FS) make it timely to update the Fraser medical community about current iGAS surveillance and public health procedures. Since mid-December 2006, eight cases of iGAS have been reported from FS – an increase from the 2-3 cases per month that have been historically reported in FS over the same seasonal time period. Six of the 8 cases have occurred in January. All were sporadic cases. Close contacts were prescribed post-exposure chemoprophylaxis, with no reports of secondary disease transmission. The provincial incidence of iGAS in January to-date is more modestly elevated (16 cases) from the average 12 cases reported for all of January over the past 3 years.

The recent 8 cases from FS involve equal numbers of males and females and span a wide age range (2 cases involving infants, up to 95 years). Cases are widely dispersed across FS: three each from North Delta and Surrey (including an elderly resident of a long term care facility) and one each from Langley and White Rock. Clinical presentations, most accompanied by bacteremia, have included pneumonia in 4 cases, and single cases of necrotizing fasciitis, septic arthritis, peritonitis, and sepsis. Two affected persons have died. Risk factors have been identified in most cases, including poorly controlled insulin dependent diabetes (2 cases), RSV co-infection (in the 2 infants), cancer, and wound infection (2 cases). Laboratory evidence to-date does not indicate a more virulent clone circulating in FS, as the 3 cases that have been serotyped have different serotypes.
Laboratory reports of invasive isolates of Group A streptococcus are routinely forwarded to public health, which coordinates the identification of close contacts who are at increased risk (about 100 fold) of developing invasive group A streptococcal disease. Post exposure antibiotic prophylaxis is offered to anyone who lived or shared sleeping quarters with the case, or had direct mucous membrane contact with the case’s oral or nasal secretions or open infected skin lesions in the week preceding onset of symptoms in the case, until 24 hours after the case was started on effective antibiotic therapy.

Recommended Actions:

1. Please be prepared to prescribe one of the recommended antibiotics (see table below) to people identified as close contacts of a case and referred to you by public health.
2. Please remember to offer varicella vaccine to susceptible children, adolescents and adults who are eligible for publicly funded vaccine. Recent chicken pox infection can be a risk factor for iGAS.
3. Laboratory physicians are reminded to ensure that isolates are forwarded to BCCDC Laboratory Services, who will arrange for shipment to the National Centre for Streptococcus in Edmonton for additional GAS serotyping. Details about packaging and shipping to BCCDC are available at: http://www.bccdc.org/content.php?item=192 (BCCDC website - click on “invasive Group A streptococcal disease” and scroll to page 6).

Please call your local health unit if you have further questions.