Southwest District Health (SWDH) is reporting an ongoing outbreak of pertussis. SWDH has investigated 115 confirmed or probable pertussis cases since January 1, 2018. SWDH reported only 4 pertussis cases for the same period (Jan 1 – August 2) in 2017. Case counts for non-outbreak years average 14 pertussis cases per year. During the first seven months of 2018, cases have been reported from all SWDH counties (Adams, Canyon, Gem, Owyhee, Payette & Washington).

Due to the highly infectious nature of pertussis and the potential for further spread, SWDH urges health care providers to maintain a heightened degree of suspicion for pertussis and to test and treat patients with clinically-compatible illness.

Clinical Manifestations

• Pertussis begins with 1-2 weeks of mild upper-respiratory tract symptoms similar to the common cold (catarrhal period). 
• Fever is usually minimal if present.
• With classic pertussis, the catarrhal period is followed by several weeks or months of paroxysmal cough, inspiratory whoop and post-tussive vomiting. Paroxysmal cough is often worse at night. Persons may not seem significantly ill between paroxysms.
• Adults and adolescents infected with pertussis often go undiagnosed due to mild illness without classic pertussis symptoms and are often the source of infection for infants and young children. Consider testing any adults / adolescents with cough persistence >= 2 weeks.
• Infants may have atypical disease with apneic spells and minimal cough or other respiratory symptoms. Infants are at highest risk for acquiring pertussis-associated complications such as pneumonia, seizures, encephalopathy, and death.

Transmission

Pertussis is a highly communicable disease with an 80% secondary attack rate among susceptible household contacts.

• Transmitted person to person via aerosolized droplets produced from a cough or sneeze or by direct contact with respiratory secretions of an infected person.
• Communicable period is 3 weeks (early catarrhal stage and first 2-3 weeks of paroxysmal stage).
• Incubation period for pertussis is 5-21 days (average 9-10 days).
• Post exposure prophylaxis (PEP) should be administered to asymptomatic household & close contacts regardless of immunization status within 21 days of the index case’s onset of cough.
• Coughing (symptomatic) household members of a pertussis patient should be treated as if they have pertussis.

Laboratory Testing

PCR (Polymerase chain reaction) testing of a nasopharyngeal (NP) swab is optimal for testing within the first 4 weeks after cough onset. Serology should not be used unless the patient has been coughing longer than 3 weeks. Testing recommendations can be found here. Some area laboratories can provide same-day results.

Pertussis Treatment and PEP (Post-exposure Prophylaxis)

To stop the spread of pertussis, antibiotic treatment is recommended for the infected person and antibiotic prophylaxis is recommended for all household and close contacts.

Azithromycin, clarithromycin, and erythromycin are all effective choices for both prophylaxis and treatment. Trimethoprim-sulfamethoxazole or TMP-SMX may be used as an alternative treatment / PEP. See the treatment / PEP table excerpted from MMWR, December 9, 2005 / 54 (RR14); 1-16 Recommended Antimicrobial Agents for the Treatment and Post exposure Prophylaxis of Pertussis at the end of the document (table 4) here.

Controlling the Outbreak

• Immunization continues to be an important part of the control for whooping cough, especially for families with infants. Immunization recommendations and schedules can be viewed here.
• Isolate outpatients to home until they have completed treatment.
• Implement a Respiratory Hygiene / Cough Etiquette policy in Healthcare & group settings. Ideas can be found here.  

Reporting Pertussis Cases

All suspect and confirmed cases of pertussis are reportable within 1 working day. Physicians, hospital & health care facility administrators, laboratory directors, and school administrators are required to report even suspect cases.

SWDH confidential reporting fax: (208) 455-5350

SWDH confidential reporting phone line: (208) 455-5442

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