Pertussis   
Annual Summary of Reportable Diseases

Pertussis, also known as whooping cough, is a contagious respiratory disease caused by the bacteria Bordetella pertussis. In 2022, 32 pertussis cases (1 per 100,000 population) were reported. Laboratory confirmation was available for 15 (47%) cases, one (1%) of which was confirmed by culture, and 15 (47%) of which were confirmed by PCR. In addition, five (16%) cases met the clinical case definition and were epidemiologically linked to laboratory confirmed cases. None of the cases (0%) met the clinical case definition only. Seventeen (53%) cases occurred in residents of the metropolitan area.

Paroxysmal coughing was the most common reported symptom, which 27 (84%) cases experienced. Approximately 12 cases (38%) reported whooping. Although commonly referred to as “whooping cough,” very young children, older individuals, and persons previously immunized may not have the typical “whoop”. Post-tussive vomiting was reported in 17 (53%) cases. Infants and young children are at the highest risk for severe disease and complications. In 2022, no cases were diagnosed with pneumonia, two were hospitalized, and no deaths occurred.

Pertussis is increasingly recognized in older children and adults. During 2022, cases ranged in age from 8 months to 76 years. No cases were diagnosed in children <6 months of age, seven (23%) in children 6 months through 4 years, twelve (39%) in children 5-12 years, one (3%) case occurred in adolescents 13-17 years, and 11 (36%) in adults ≥18 years. The median age of cases was 24 years. Infection in older children and adults may result in exposure of unprotected infants. During 2022, two cases were in infants <1 year of age. A likely source of exposure wasn’t identified for those cases. Vaccination is recommended for pregnant people at ≥20 weeks gestation during each pregnancy to protect young infants. Ensuring up-to-date vaccination of children, adolescents, and adults, especially those in contact with young children, is also important. Children aged 7 and under receive the DTaP vaccine, while older children and adults receive the Tdap vaccine. Vaccinating adolescents and adults with Tdap will decrease the incidence of pertussis in the community and thereby minimize infant exposures.

Although unvaccinated children are at highest risk for pertussis, fully immunized children may also develop disease, particularly as the number of years since vaccination increases. Disease in those previously immunized is usually mild. Efficacy for currently licensed DTaP vaccines is estimated to be 71-84% in preventing typical disease within the first three years of completing the series. Waning immunity sharply increases at 7 years of age, and most are susceptible by 11-12 years of age when the Tdap booster is recommended. Recent studies suggest that immunity wanes sharply two years from receipt of Tdap. Of the 13 (40%) cases who were 7 months to 6 years of age, three (25 %) were known to have received at least a primary series of 3 doses of DTP/ DTaP vaccine prior to onset of illness; 6 (46%) received fewer than three doses and were considered preventable cases.

Reporting rules require clinical isolates of B. pertussis be submitted to the MDH Public Health Lab (PHL) to track changes in circulating strains. Isolates were not subtyped using pulsed-field gel electrophoresis (PFGE). Nationally, isolates have had low minimum inhibitory concentrations (falling within the reference range for susceptibility) to erythromycin and azithromycin. Only 11 erythromycin-resistant B. pertussis cases have been identified in the United States. Laboratory tests should be performed on all suspected cases. B. pertussis is rarely identified late in the illness, therefore, a negative culture does not rule out disease. A positive PCR result is considered confirmatory in patients with a 2-week history of cough illness. PCR can detect non-viable organisms. Consequently, a positive PCR result does not necessarily indicate current infectiousness. Patients with a 3-week or longer history of cough illness, regardless of PCR result, may not benefit from antibiotic therapy. Whenever possible, culture should be done in conjunction with PCR testing. Serological tests may be useful for those with coughs >2 weeks.

Pertussis remains endemic despite an effective vaccine and high coverage rates with the primary series. Reported incidence of pertussis has consistently increased over the past 10 years, particularly in middle school-aged children, adolescents, and adults.

• For up to date information see: Pertussis (Whooping Cough)

In 2021, 29 pertussis cases (1 per 100,000 population) were reported. Laboratory confirmation was available for 26 (90%) cases, none (0%) of which were confirmed by culture and 8 (28%) of which were confirmed by PCR. In addition, 7 (24%) cases met the clinical case definition and were epidemiologically linked to laboratory confirmed cases, and 3 (10%) met the clinical case definition only. Twenty (69%) cases occurred in residents of the metropolitan area.

Paroxysmal coughing was the most common reported symptom, which 24 (83%) cases experienced. Approximately 36% (10) reported whooping. Although commonly referred to as “whooping cough,” very young children, older individuals, and persons previously immunized may not have the typical “whoop”. Post-tussive vomiting was reported in 14 (49%) cases. Infants and young children are at the highest risk for severe disease and complications. In 2021, no cases were diagnosed with Pneumonia, none were hospitalized, and no deaths occurred.

Pertussis is increasingly recognized in older children and adults. During 2021, cases ranged in age from 9 months to 74 years. No cases were diagnosed in children <6 months of age, 5 (19%) in children 6 months through 4 years, none in children 5-12 years, two (8%) cases occurred in adolescents 13-17 years, and 19 (73%) in adults ≥18 years. The median age of cases was 38 years. Infection in older children and adults may result in exposure of unprotected infants. During 2021, one case was in an infant <1 year of age. A likely source of exposure wasn’t identified for that case. ACIP recommends vaccination of women at ≥20 weeks gestation during each pregnancy to protect young infants. Ensuring up-to-date vaccination of children, adolescents, and adults, especially those in contact with young children, is also important. Children aged 7 and under receive the DTaP vaccine, while older children and adults receive the Tdap vaccine. Vaccinating adolescents and adults with Tdap will decrease the incidence of pertussis in the community and thereby minimize infant exposures.

Although unvaccinated children are at highest risk for pertussis, fully immunized children may also develop disease, particularly as the number of years since vaccination increases. Disease in those previously immunized is usually mild. Efficacy for currently licensed DTaP vaccines is estimated to be 71-84% in preventing typical disease within the first 3 years of completing the series. Waning immunity sharply increases at 7 years of age, and most are susceptible by 11-12 years of age when the Tdap booster is recommended. Recent studies suggest that immunity wanes sharply 2 years from receipt of Tdap. Of the 8 (28%) cases who were 7 months to 6 years of age, 5 (63%) were known to have received at least a primary series of 3 doses of DTP/ DTaP vaccine prior to onset of illness; 3 (38%) received fewer than 3 doses and were considered preventable cases.

Reporting rules require clinical isolates of Bordetella pertussis be submitted to the PHL to track changes in circulating strains. Isolates were not subtyped using pulsed-field gel electrophoresis (PFGE). Nationally, isolates have had low minimum inhibitory concentrations (falling within the reference range for susceptibility) to erythromycin and azithromycin. Only 11 erythromycin-resistant B. pertussis cases have been identified in the United States.

Laboratory tests should be performed on all suspected cases. B. pertussis is rarely identified late in the illness, therefore, a negative culture does not rule out disease. A positive PCR result is considered confirmatory in patients with a 2-week history of cough illness. PCR can detect non-viable organisms. Consequently, a positive PCR result does not necessarily indicate current infectiousness. Patients with a 3-week or longer history of cough illness, regardless of PCR result, may not benefit from antibiotic therapy. Whenever possible, culture should be done in conjunction with PCR testing. Serological tests may be useful for those with coughs >2 weeks.

Pertussis remains endemic despite an effective vaccine and high coverage rates with the primary series. Reported incidence of pertussis has consistently increased over the past 10 years, particularly in middle school-aged children, adolescents, and adults.

• For up to date information see: Pertussis (Whooping Cough)

In 2020, 147 pertussis cases (3 per 100,000 population) were reported. Laboratory confirmation was available for 122 (83%) cases, 6 (5%) of which were confirmed by culture and 122 (83%) of which were confirmed by PCR. In addition, 37 (25%) cases met the clinical case definition and were epidemiologically linked to laboratory confirmed cases, and 2 (8%) met the clinical case definition only. Sixty-five (44%) cases occurred in residents of the metropolitan area.

Paroxysmal coughing was the most commonly reported symptom, which 118 (80%) cases experienced. Approximately 22% (33) reported whooping. Although commonly referred to as “whooping cough,” very young children, older individuals, and persons previously immunized may not have the typical “whoop”. Post-tussive vomiting was reported in 65 (44%) cases. Infants and young children are at the highest risk for severe disease and complications. Pneumonia was diagnosed in 3 (8%) cases, only 1 (33%) of which was an infant; 1 was 2-16 years old, and 1 was 20-69 years old. Five (3%) cases were hospitalized; 3 hospitalized patients were <6 months of age. No deaths occurred.

Pertussis is increasingly recognized in older children and adults. During 2020, cases ranged in age from <1 month to 83 years. Thirty-seven (25%) cases occurred in adolescents 13-17 years, 8 (33%) in children 5-12 years, 28 (19%) in adults ≥18 years, 23 (41%) in children 6 months through 4 years, and 6 (4%) in infants <6 months of age. The median age of cases was 11 years. Infection in older children and adults may result in exposure of unprotected infants. During 2020, 7 cases were in infants <1 year of age. A likely source of exposure was identified for 3 of those cases; all 3 were infected by a child <13 years of age. ACIP recommends vaccination of women at ≥20 weeks gestation during each pregnancy in an effort to protect young infants. Ensuring up-to-date vaccination of children, adolescents, and adults, especially those in contact with young children is also important. Vaccinating adolescents and adults with Tdap will decrease the incidence of pertussis in the community and thereby minimize infant exposures.

Although unvaccinated children are at highest risk for pertussis, fully immunized children may also develop disease, particularly as the number of years since vaccination increase. Disease in those previously immunized is usually mild. Efficacy for currently licensed DTaP vaccines is estimated to be 71-84% in preventing typical disease within the first 3 years of completing the series. Waning immunity sharply increases at 7 years of age, and most are susceptible by 11-12 years of age when Tdap booster is recommended. Recent studies suggest that immunity wanes sharply 2 years from receipt of Tdap. Of the 36 (29%) cases who were 7 months to 6 years of age, 10 (28%) were known to have received at least a primary series of 3 doses of DTP/ DTaP vaccine prior to onset of illness; 22 (61%) received fewer than 3 doses and were considered preventable cases.

Reporting rules require clinical isolates of Bordetella pertussis be submitted to the PHL in order to track changes in circulating strains. Isolates for all 6 culture-confirmed cases were received and sub-typed, with six distinct PFGE patterns identified. Nationally, isolates have had low minimum inhibitory concentrations (falling within the reference range for susceptibility) to erythromycin and azithromycin. Only 11 erythromycin-resistant B. pertussis cases have been identified in the United States.

Laboratory tests should be performed on all suspected cases. However, B. pertussis is rarely identified late in the illness; therefore, a negative culture does not rule out disease. A positive PCR result is considered confirmatory in patients with a 2-week history of cough illness. PCR can detect non-viable organisms. Consequently, a positive PCR result does not necessarily indicate current infectiousness. Patients with a 3-week or longer history of cough illness, regardless of PCR result, may not benefit from antibiotic therapy. Whenever possible, culture should be done in conjunction with PCR testing. Serological tests may be useful for those with coughs >2 weeks.

Pertussis remains endemic despite an effective vaccine and high coverage rates with the primary series. Reported incidence of pertussis has consistently increased over the past 10 years, particularly in middle school-aged children, adolescents, and adults.

• For up to date information see: Mumps

In 2019, 469 pertussis cases (8 per 100,000 population) were reported. Laboratory confirmation was available for 320 (73%) cases, 36 (11%) of which were confirmed by culture and 284 (89%) of which were confirmed by PCR. In addition, 66 (21%) cases met the clinical case definition and were epidemiologically linked to laboratory confirmed cases, and 37 (12%) met the clinical case definition only. Two hundred thirty-five (50%) cases occurred in residents of the metropolitan area.

Paroxysmal coughing was the most commonly reported symptom, which 432 (92%) cases experienced. Approximately one third (138) reported whooping. Although commonly 14 DCN 47;1 2021 referred to as “whooping cough,” very young children, older individuals, and persons previously immunized may not have the typical “whoop”. Post-tussive vomiting was reported in 206 (44%) cases. Infants and young children are at the highest risk for severe disease and complications. Pneumonia was diagnosed in 17 (4%) cases, only 3 (18%) of which were in infants; 3 (18%) were 2 to 16 years old, 9 (53%) were 20 to 70 years old. Eleven (2%) cases were hospitalized; 1 hospitalized patient was <6 months of age. One death occurred.

Pertussis is increasingly recognized in older children and adults. During 2019, cases ranged in age from <1 month to 92 years. Eighty-six (18%) cases occurred in adolescents 13-17 years, 149 (32%) in children 5-12 years, 109 (23%) in adults ≥18 years, 80 (17%) in children 6 months through 4 years, and 15 (5%) in infants <6 months of age. The median age of cases was 11 years. Infection in older children and adults may result in exposure of unprotected infants. During 2019, 16 cases were in infants <1 year of age. A likely source of exposure was identified for all of those cases; 2 were infected by adults ≥18 years, 2 by an adolescent 13-17 years, 12 by a child <13 years. ACIP recommends vaccination of women at ≥20 weeks gestation during each pregnancy in an effort to protect young infants. Ensuring up-to-date vaccination of children, adolescents, and adults, especially those in contact with young children is also important. Vaccinating adolescents and adults with Tdap will decrease the incidence of pertussis in the community and thereby minimize infant exposures.

Although unvaccinated children are at highest risk for pertussis, fully immunized children may also develop disease, particularly as the number of years since vaccination increase. Disease in those previously immunized is usually mild. Efficacy for currently licensed DTaP vaccines is estimated to be 71-84% in preventing typical disease within the first 3 years of completing the series. Waning immunity sharply increases at 7 years of age, and most are susceptible by 11-12 years of age when Tdap booster is recommended. Recent studies suggest that immunity wanes sharply 2 years from receipt of Tdap. Of the 112 (24%) cases who were 7 months to 6 years of age, 44 (40%) were known to have received at least a primary series of 3 doses of DTP/ DTaP vaccine prior to onset of illness; 66 (59%) received fewer than 3 doses and were considered preventable cases.

Reporting rules require clinical isolates of Bordetella pertussis be submitted to the PHL in order to track changes in circulating strains. Isolates for 33 (79%) culture-confirmed cases were received and sub-typed, with four distinct PFGE patterns identified. Nationally, isolates have had low minimum inhibitory concentrations (falling within the reference range for susceptibility) to erythromycin and azithromycin. Only 11 erythromycin-resistant B. pertussis cases have been identified in the United States.

Laboratory tests should be performed on all suspected cases. However, B. pertussis is rarely identified late in the illness; therefore, a negative culture does not rule out disease. A positive PCR result is considered confirmatory in patients with a 2-week history of cough illness. PCR can detect non-viable organisms. Consequently, a positive PCR result does not necessarily indicate current infectiousness. Patients with a 3-week or longer history of cough illness, regardless of PCR result, may not benefit from antibiotic therapy. Whenever possible, culture should be done in conjunction with PCR testing. Serological tests may be useful for those with coughs >2 weeks.

Pertussis remains endemic despite an effective vaccine and high coverage rates with the primary series. Reported incidence of pertussis has consistently increased over the past 10 years, particularly in middle school-aged children, adolescents, and adults.

• For up to date information see: Pertussis (Whooping Cough)

In 2018, 397 pertussis cases (7 per 100,000 population) were reported. Laboratory confirmation was available for 280 (71%) cases, 19 (7%) of which were confirmed by culture and 262 (94%) by PCR. In addition, 60 (15%) cases met the clinical case definition and were epidemiologically linked to laboratory confirmed cases, and 56 (15%) met the clinical case definition only. One hundred ninety-two (48%) cases occurred in residents of the metropolitan area.

Paroxysmal coughing was the most commonly reported symptom, which 369 (93%) cases experienced. Approximately one third (118) reported whooping. Although commonly referred to as “whooping cough,” very young children, older individuals, and persons previously immunized may not have the typical “whoop”. Post-tussive vomiting was reported in 185 (47%) cases. Infants and young children are at the highest risk for severe disease and complications. Pneumonia was diagnosed in 8 (2%) cases, only 2 of which were in infants; 3 were 2 to 16 years old, 2 were 20 to 70 years old. Five (1%) cases were hospitalized; 2 (33%) hospitalized patients were <6 months of age. No deaths occurred.

Pertussis is increasingly recognized in older children and adults. During 2018, cases ranged in age from <1 month to 86 years. One hundred (25%) cases occurred in adolescents 13-17 years, 105 (26%) in children 5-12 years, 92 (23%) in adults ≥18 years, 74 (19%) in children 6 months through 4 years, and 14 (4%) in infants <6 months of age. The median age of cases was 13 years. Infection in older children and adults may result in exposure of unprotected infants. During 2018, 24 cases were in infants <1 year of age. A likely source of exposure was identified for 11 of those cases; 3 were infected by adults ≥18 years (one mother and two fathers), 1 by an adolescent 13-17 years, 6 by a child <13 years of age, and for 1 the age was unknown. Eleven infant cases had no identified source of infection. ACIP recommends vaccination of women at ≥20 weeks gestation during each pregnancy in an effort to protect young infants. Ensuring up-to-date vaccination of children, adolescents, and adults, especially those in contact with young children is also important.

Although unvaccinated children are at highest risk for pertussis, fully immunized children may also develop disease, particularly as the number of years since vaccination increase. Disease in those previously immunized is usually mild. Efficacy for currently licensed DTaP vaccines is estimated to be 71-84% in preventing typical disease within the first 3 years of completing the series. Waning immunity sharply increases at 7 years of age, and most are susceptible by 11-12 years of age when Tdap booster is recommended. Recent studies suggest that immunity wanes sharply 2 years from receipt of Tdap. Of the 97 (24%) cases who were 7 months to 6 years of age, 40 (41%) were known to have received at least a primary series of 3 doses of DTP/DTaP vaccine prior to onset of illness; 54 (56%) received fewer than 3 doses and were considered preventable cases.

Isolates of Bordetella pertussis must be submitted to the PHL in order to track changes in circulating strains. Isolates for 17 (90%) culture-confirmed cases were received and sub-typed, with two distinct PFGE patterns identified. Nationally, isolates have had low minimum inhibitory concentrations (falling within the reference range for susceptibility) to erythromycin and azithromycin. Only 11 erythromycinresistant B. pertussis cases have been identified in the United States.

Laboratory tests should be performed on all suspected cases. However, B. pertussis is rarely identified late in the illness; therefore, a negative culture does not rule out disease. A positive PCR result is considered confirmatory in patients with a 2-week history of cough illness. PCR can detect non-viable organisms. Consequently, a positive PCR result does not necessarily indicate current infectiousness. Patients with a 3-week or longer history of cough illness, regardless of PCR result, may not benefit from antibiotic therapy. Whenever possible, culture should be done in conjunction with PCR testing. Serological tests may be useful for those with coughs >2 weeks.

• For up to date information see: Pertussis (Whooping Cough)

• Archive of Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health
  Archive of past summaries (years prior to 2023 are available as PDFs).