From the Infectious Diseases Society of America An Old Disease in a New Form
TORONTO, Canada—Considered an “old” disease by many physicians, pertussis (commonly referred to as whooping cough) is making a comeback in the United States and is becoming a particular concern among older age-groups, several new studies presented at the Infectious Diseases Society of America annual meeting show.
These data include evidence that immunity diminishes in adolescence, suggesting that major efforts are needed to ensure that all adolescents and adults are re-immunized.
Studies presented showing the growing incidence of pertussis infection in Seattle, San Francisco, and Philadelphia were considered to be indicative of the pattern nationwide. Two of the studies showed that pertussis disproportion-ately affects minorities, particularly Hispanics. Although the incidence of pertussis has been rising for more than a decade, the problem has escalated dramatically in the past 5 years.
For example, the number of cases reported in the Seattle area jumped from 39 in 2001 to 280 in 2003, a >7-fold increase (Table). The largest increase was in those aged ≥20 years (11-fold) and in adolescents aged 10 to 19 (>5-fold). In 62% of cases involving an infant, a household member was a potential source of infection. Most of the sources were adolescents and adults.
“The thought is that the adults who have waning immunity are having mild disease that is harder to pick up, and then they are passing it on to infants, who suffer severe complications,” lead investigator Christopher Czaja, MD, of the University of Washington, Seattle, told . “Pertussis can present as a milder cough illness in adults. Often adults don’t present with the classic symptoms, like whooping. So…physicians need to try to pick the disease up early to prevent transmission. There is also a new vaccine that is now available for adults and that should be used aggressively to prevent the disease.”
Approximately 10% to 12% of all pertussis cases in Western countries occur in persons aged >15 years, according to a recent study (. 2006; 130:1547-1553). Although in the United States most pertussis-related deaths involve infants, a substantial number of deaths are also being reported in older age-groups, this study demonstrates.
The rise in pertussis infection among adolescents is due, in part, to their increasing susceptibility at approximately 6 to 10 years after their childhood vaccination. Because of this, the FDA recently recommended booster shots for adolescents and adults that contain a combination of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis antigens.
Analysis of 160 infant pertussis cases reported in 3 San Francisco counties between 2000 and 2004 showed that 14% had pneumonia, and 77% were hospitalized. A source was identified in nearly half of these cases, and in 58% of them the source was a parent.