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19-03-2012 | General practice | Article

Marked upsurge in pertussis in California


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MedWire News: Over 6000 cases of pertussis were recorded in the US state of California in 2010, the largest upsurge in 60 years, according to the results of an epidemiologic study.

The researchers say it mirrors a worldwide trend based on waning immunity in adolescents and adults who have become a major source of infection for unimmunized infants.

"The medical community has a responsibility to do the most it can to limit the spread of pertussis and ensure that this upsurge does not persist," say Greg Marconi (Children's Hospital Los Angeles) and colleagues in Pediatric Emergency Care.

Pertussis (whooping cough) is a highly contagious infectious disease, characterized by severe paroxysmal coughing episodes that typically end with an inspiratory whoop.

Even with the introduction of vaccination in the 1940s, pertussis continues to be a common worldwide infection in pediatric and adult populations, typically showing an increase in the number of reported cases every 2 to 5 years.

Since late 2009, an epidemic of pertussis has been documented in California.

For the current study, the researchers performed a retrospective review of all specimens submitted for Bordetella pertussis polymerase chain reaction assay from the emergency department of a large tertiary care children's hospital from January 2009 to August 2010.

They found that the total number of positive cases increased from 13 to 94, a 723% increase at their institution over the time period studied. The median monthly number of positive specimens was 1.5 for 2009 and 6.5 for 2010.

This tallies with data from the California Department of Public Health, which in their October 26, 2010 pertussis report, recorded 6257 confirmed, probable, and suspected cases of pertussis for the state.

This is an almost 12-fold increase on the same period in 2009 when there were 530 reported cases, and the most reported cases in California in the last 60 years.

Discussing the findings, Marconi et al note that immunity against the pertussis infection persists for 3 to 5 years after receiving the vaccination and then declines until it is not measureable after 12 years.

Although most US states require a pertussis booster shot for middle school students, California is not currently one of these. However, a new state law will now require all 7th to 12th grade students to receive a pertussis booster vaccination before starting school in fall 2011.

"Revaccination is an important component at protecting young infants against pertussis now and will continue to be so in the future," Marconi et al conclude.

By Andrew Czyzewski

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