Outbreaks

Español: Brotes

Pertussis is an endemic (common) disease in the United States, with peaks in disease every 3 to 5 years and frequent outbreaks. In 2010, 27,550 cases of pertussis were reported — and many more cases go unreported. The primary goal of pertussis outbreak control efforts is to decrease morbidity (amount of disease) and mortality (death) among infants; a secondary goal is to decrease morbidity among persons of all ages.

Pertussis outbreaks can be difficult to identify and manage. Other respiratory pathogens often cause clinical symptoms similar to pertussis, and co-circulation with other pathogens (bacterial and viral) does occur. In order to respond appropriately (e.g., provide appropriate antibiotic prophylaxis), it is important to confirm that Bordetella pertussis is circulating in the outbreak setting and to determine whether other pathogens are contributing to the outbreak. Polymerase chain reaction (PCR) tests vary in specificity, so obtaining culture confirmation of pertussis for at least one suspicious case is recommended any time there is suspicion of a pertussis outbreak.

Pseudo outbreaks of pertussis have resulted because of false positive test results with PCR. This underscores the importance of recognizing clinical signs and symptoms and practicing careful laboratory testing.

Institutional outbreaks of pertussis are common. Outbreaks at middle and high schools can occur as protection from childhood vaccines fades. In school outbreaks, prophylaxis is recommended for close classroom and team contacts — and the pertussis booster vaccine (Tdap) depending on age. Pertussis outbreaks in hospitals and other clinical settings can put infants and other patients at risk.

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Questions and Answers

Outbreak-Related Questions and Answers

Outbreak Trends

Compared to 2010, fewer pertussis cases were reported in 2011. Sporadic outbreaks occurred in several states.

During the first half of 2012, increased pertussis cases or outbreaks have been reported in a majority of states. As of September 20, 2012, 48 states and Washington, D.C. have reported increases in disease compared with the same time period in 2011. See the table below for which states have the highest reported rates of pertussis.

Provisional counts from our surveillance system indicate that nearly 29,000 cases of pertussis were reported to CDC through September 20, 2012. 14 pertussis-related deaths have been reported during that same time period. The majority of deaths continue to occur among infants younger than 3 months of age. The incidence rate of pertussis among infants exceeds that of all other age groups. The second highest rates of disease are observed among children 7 through 10 years old. Rates are also increased in adolescents 13 and 14 years of age.

See the annual number of reported pertussis cases going back to 2000 or view the latest number of cases reported by states and territories. Since there is a lag in reporting to CDC, the most up-to-date information for states and territories is available from local health departments.

States with incidence of pertussis the same or higher than the national incidence (as of September 20, 2012), which is 9.3/100,000 persons

Wisconsin	78.6	New Mexico	22.9	Arizona	11.2
Minnesota	63.5*	Alaska	18.9	Idaho	11.0
Washington	58.1	Oregon	18.3	Pennsylvania	11.0
Montana	43.7	Kansas	14.6	Colorado	11.0
Vermont	42.0	New York State	12.4	Missouri	10.6
Maine	37.5	North Dakota	11.5	Kentucky	9.9
Iowa	37.0	Illinois	11.4	-	-
Utah	29.3	New Hampshire	11.4	-	-

*Only a small subset of Minnesota pertussis cases have been reported through NNDSS for 2012. This data was accessed from the Minnesota Department of Health web site.

Trends in pertussis cases over the last century from National Notifiable Diseases Surveillance System (NNDSS) reports 1922-2011 [106KB, 1 page]

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Recent Outbreak Activity

Localized outbreaks of pertussis are not uncommon and occur throughout the year. Some examples of pertussis activity in the US include:

• A pertussis epidemic was declared in Washington on April 3, 2012. There have been 4,115 cases reported statewide through September 15, 2012, compared to 427 reported cases in 2011 during the same time period. There were 965 cases reported statewide in 2011 compared to 608 reported cases in 2010. Visit the Washington State Department of Health for the most recent information.
• Minnesota is experiencing high rates of pertussis in 2012. As of September 13, 2012, 3,369 cases have been reported statewide. 661 pertussis cases were reported in 2011. Visit the Minnesota Department of Health for the most recent information.
• High rates of pertussis are being reported in Wisconsin. As of September 3, 2012, 4,181 cases have been reported. During 2011, 1,192 probable and confirmed cases were reported. Visit the Wisconsin Department of Health Services for the most recent information.
• Colorado began to describe its increases in pertussis cases as epidemic on August 20, 2012. As of September 8, 2012, 849 cases have been reported in 2012 compared to a 2007-2011 average of 158 cases for the same time period. Visit the Colorado Department of Public Health and Environment for the most recent information.

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Outbreak Articles

• Pertussis Epidemic — Washington, 2012
  MMWR July 20, 2012; 61(28):517-22
• Pertussis Pseudo-outbreak linked to specimens contaminated by Bordetella pertussis DNA From clinic surfaces. Mandal et al., 2011. Pediatrics, 129(2), e424-30.
• Notes from the Field: Pertussis — California, January–June 2010
  MMWR June 9, 2010; 59(26):817
• Use of Mass Tdap Vaccination to Control an Outbreak of Pertussis in a High School — Cook County, Illinois, September 2006–January 2007
  MMWR July 25, 2008;57(29):796-9
• Outbreaks of Respiratory Illness Mistakenly Attributed to Pertussis — New Hampshire, Massachusetts, and Tennessee, 2004–2006
  MMWR August 24, 2007; 56(33):837-842
• Pertussis Outbreak in an Amish Community — Kent County, Delaware, September 2004–February 2005
  MMWR August 4, 2006;55(30):817-21
• Outbreaks of Pertussis Associated with Hospitals — Kentucky, Pennsylvania, and Oregon, 2003
  MMWR January 28, 2005;54(3):67-71
• School-Associated Pertussis Outbreak — Yavapai County, Arizona, September 2002–February 2003
  MMWR March 19, 2004;53(10):216-9
• Pertussis Outbreak among Adults at an Oil Refinery — Illinois, August–October 2002
  MMWR January 10, 2003;52(01):1-4

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Resources

• Surveillance Manual's Chapter on Pertussis
  Manual from the Surveillance of Vaccine-Preventable Diseases textbook.
• CDC and CSTE Case Definition for NNDSS
• Guidelines for the Control of Pertussis Outbreaks
• Outbreak Control, Surveillance Manual's Chapter on Pertussis
  Manual from the Surveillance of Vaccine-Preventable Diseases textbook
• For Parents and Patients
  What parents need to know, e-cards, flyer (protect yourself and your baby), hear the cough...