The day care in Vancouver, Washington associated with the recent outbreak of E. coli 0157:H7 is to remain closed while workers continue to undergo testing, according to a report in the Clark County Columbian:
Dr. Alan Melnick, county health officer, said Fletch Family Daycare will remain closed until staff members who have tested positive for E. coli or displayed symptoms have two negative E. coli tests separated by 24 hours.
The day care center was closed on April 2, and the original closure was intended to span 10 days. County officials are requiring that children with either a positive culture for E. coli O157:H7 or symptoms of an infection must also have two negative tests with the requisite 24 hour separation before returning to any day care.
New details about the outbreak and the investigation have come to light. While there were four children hospitalized with E. coli O157:H7 infections, it has been reported that seven people who did not show sign of illness also tested positive for E. coli O157:H7. Cases such as these, termed "asymptomatic" infections, are not unheard of. It is difficult to determine, however, how often such asymptomatic infections occur. One study reported:
Cases of asymptomatic E. coli O157:H7 infection have occasionally been detected in outbreaks, but the incidence rates are difficult to estimate because stool samples from asymptomatic persons are rarely obtained for culturing. In an outbreak in Canada that involved kindergarten children, 31% of those exposed to the implicated source (19 of 62) were asymptomatic. Fifty-three percent of the asymptomatic children (10 of 19) had laboratory evidence of E. coli O157:H7.
Thankfully, Dr. Melnick believes the threat is over, saying, “At this point, health officials believe that the outbreak has been contained and does not pose a threat to others in the community."