Content Information
A. Purpose of Surveillance and Reporting
- To identify sources and sites of transmission and any additional cases.
- To identify close contacts and recommend prophylaxis for those at risk for severe complications due to pertussis or those who may come in contact with those at risk for severe complications due to pertussis.
- To monitor the effectiveness of outbreak control strategies.
- To provide data for monitoring the effectiveness of new vaccine formulations.
- To analyze vaccination status by age to determine whether the problem is predominantly failure to vaccinate or vaccine failure.
- To characterize the epidemiology of pertussis disease in Iowa.
B. Laboratory and Healthcare Provider Reporting Requirements
Iowa Administrative Code 641-1.3(139) stipulates that the laboratory and the healthcare provider must report. The preferred method of reporting is by utilizing the Iowa Disease Surveillance System (IDSS). However, if IDSS is not available, the reporting number for IDPH Center for Acute Disease Epidemiology (CADE) is (800) 362-2736; fax number (515) 281-5698, mailing address:
Iowa HHS, CADE
Lucas State Office Building, 5th Floor
321 E. 12th St
Des Moines, IA 50319-0075
C. Laboratory Testing
Who should be tested for pertussis?
Any person presenting with symptoms consistent with pertussis, regardless of contact with a case or an outbreak situation.
Who should not be tested for pertussis?
Asymptomatic persons, regardless of contact with a case or an outbreak situation.
Do symptomatic contacts of laboratory confirmed cases need to be tested?
It is not necessary to test the first “ring” out from a laboratory confirmed case if the contact was exposed while the lab confirmed case was infectious, proper incubation time has elapsed, and the signs and symptoms are compatible with pertussis.
It is recommended that the second “ring” out from a laboratory confirmed case be tested (e.g., contacts of a contact of a laboratory confirmed case).
What test should be performed?
Polymerase chain reaction (PCR) testing is recommended and should be used for laboratory confirmation.
Serologic testing is not yet standardized and is not widely available. Due to lack of association between antibody levels and immunity to pertussis, results of serologic testing are difficult to interpret.
Where can testing be performed?
PCR testing is available at the State Hygienic Laboratory. For more information on testing services provided by SHL, call 319-335-4500 or visit: www.shl.uiowa.edu/.
Specimen Collection and Handling
- PCR is a very sensitive test and precautions should be taken to prevent cross-contamination of specimens (i.e., changing gloves and use of sterile scissors or decontamination of scissors using bleach solution) for each patient.
- If possible, specimens should be collected prior to start of antibiotic treatment. However, PCR detects both live and dead bacteria, so it does not indicate active disease.
- A properly obtained nasopharyngeal swab, wash, or aspirate is essential for optimal test results. Collection and handling instructions for each specimen type are described below.
- Nasopharyngeal swab testing kits consisting of slides, media and swabs in mailing containers can be ordered from the State Hygienic Laboratory at (319) 335-4500.
Nasopharyngeal Swab:
- Gently insert nasopharyngeal swab into a nostril until the posterior nasopharynx is reached. Use a dacron or calcium alginate swab, not cotton.
- Leave the swab in place for 10 to 30 seconds.
- Slowly remove with a rotating motion.
- Place swab tip into 1.5 ml screw cap tube. Cut the excess length of the wire shaft with a sterile scissors, and cap the tube tightly. Treatment of scissors with 10 percent bleach prior to use is effective in removing contamination with bacterial DNA from other sources.
- Repeat process to collect a second swab, and place in the glass vial containing the Regan-Lowe transport medium. Cut off excess length of shaft, and cap the tube tightly.
- If the kit does not contain Regan-Lowe transport medium, then place second swab in the replicate 1.5 ml screw cap tube provided in the kit.
- Label specimens, wrap in absorbent material, and place in a biohazard bag and seal. Use a single biohazard bag for each patient’s specimens. Place the completed Test Request Form in the outside pocket of the biohazard bag.
Nasal Wash: Instill several milliliters of sterile saline into nostrils while patient’s head is tilted back. Bring patient’s head forward and catch saline flowing from the nostrils in a small container. Pour specimen (minimum volume 0.2 ml) into the 1.5 ml sterile tube contained in the kit.
Nasopharyngeal Aspirate: A small catheter with a suction trap or bulb aspirator is inserted through the nostrils into the nasopharynx. Apply suction while slowly removing the catheter or aspirator tip. The catheter or aspirator should be flushed with sterile saline or viral transport medium and contents (minimum volume 0.2 ml) placed into the 1.5 ml sterile tube contained in the kit.
Test result interpretation:
Positive results indicate that the bacterium was detected in the specimen.
Negative results indicate that the bacterium was not detected in the specimen. Note: negative results may occur if the patient is tested greater than three weeks after symptom onset.
Equivocal results occur occasionally, meaning the PCR test does not clearly indicate a positive OR negative result. The clinician must then determine if the clinical symptoms and epidemiologic factors indicate a likely pertussis diagnosis or not. Public health follow up should depend on this determination.
Indeterminate results rarely occur. Indeterminate results are generally caused by an inadequate specimen or interfering substances in the specimen that inhibited the reaction. Retesting can be considered. Ultimately, the clinician must determine if the clinical symptoms and epidemiologic factors indicate a likely pertussis diagnosis or not. Public health follow up should depend on this determination.
D. Local Public Health Agency (LPHA) Follow-Up Responsibilities
Case Investigation
Pertussis follow-up and case investigation is undertaken by the local public health agency (LPHA) and coordinated, if necessary, with IDPH Center for Acute Disease Epidemiology (CADE).
LPHA is responsible for conducting pertussis follow-up. Case investigation includes but is not limited to the following steps.
- Confirm the case’s diagnosis.
- Conduct the case interview, using the case interview form included this chapter and also in the Iowa Disease Surveillance System (IDSS).
- Identify all household contacts, close contacts at high risk of developing severe illness, and contacts who themselves have close contact with individuals at high risk.
- Determine whether any of the identified contacts are symptomatic.
- Recommend prophylaxis for asymptomatic close contacts (See Section 3. C. Post Exposure Antimicrobial Prophylaxis Recommendations).
- Symptomatic contacts should receive antibiotic treatment, possibly test, and be isolated until they have completed the first five days of the full course of an appropriate antibiotic (symptomatic contacts who refuse antibiotics should stay home through 21 days after cough onset). Symptomatic contacts are considered “epi-linked cases” and should be investigated as new cases and reported accordingly into the Iowa Disease Surveillance System (IDSS).
- If symptomatic contacts have already coughed for more than 21 days at the time of diagnosis, the individual is no longer contagious to others. In most cases neither treatment nor isolation are indicated (See Section 3. B. Recommended Treatment Protocol on page 6 and Section 3. C. Post Exposure Antimicrobial Prophylaxis Recommendations.)
- Use the Iowa Disease Surveillance System (IDSS) to complete the Pertussis Case Investigation form. If IDSS is not available, paper forms can be used. This will drive the investigation. If paper forms are used, fax to the Center for Acute Disease Epidemiology (CADE) at (515)281-5698.
Contact the assigned field epidemiologist with questions or if assistance is needed. (800-362-2736)