A doctor considers the following when making a preliminary diagnosis of whooping cough (pertussis):

• Symptoms. A health professional may suspect whooping cough when a person has recently had cold symptoms and a dry, hacking cough that progresses to bursts of uncontrollable, often violent coughing that may make it temporarily impossible to breathe. The characteristic whooping noise sometimes occurs when the person tries to inhale quickly through airways narrowed by inflammation. Babies may have flushed cheeks, a pale or bluish complexion from lack of oxygen, and bulging or watery eyes. A baby may also stick out his or her tongue, push the chest forward, or flail arms and legs in distress. Fever, sore throat, and wheezing are usually absent or very mild with whooping cough. When present, these symptoms can help a doctor distinguish between whooping cough and other conditions with similar symptoms, such as a cold or bronchitis.
• Immunization status. An important consideration when making a preliminary diagnosis of whooping cough (pertussis) is whether a person's immunizations against pertussis are up to date.
  • DTaP. Children start getting their pertussis immunizations at age 2 months. A total of 5 injections (shots) are given at different times until ages 4 to 6 years. The pertussis vaccine is given along with the vaccines for diphtheria and tetanus in a single shot. For children, ages 6 and younger, the vaccine is called DTaP.
  • Tdap. Combination booster vaccines (for pertussis, diphtheria, and tetanus), known as Tdap, are available for people ages 10 to 64. (Until recently, no vaccine was available for pertussis after age 6.) A booster dose of Tdap is recommended for adolescents ages 11 to 12.¹ And any teen, adult, or health professional who expects to have close contact with a baby less than 1 year old should also get a shot.
    • Teens who have not had a booster shot should get one between ages 13 and 18.¹ For routine prevention, adults 19 to 64 years of age should have one dose of this booster shot instead of Td (tetanus and diphtheria) vaccine.² People who get booster shots for whooping cough get continued protection, which helps prevent the spread of the disease. This is especially important for protecting babies younger than 2 months and others who are at high risk for becoming infected and developing complications from the disease.
• Community outbreaks. Whooping cough may be suspected when other cases of whooping cough have recently been reported within the local community.

Doctors can diagnose whooping cough by testing mucus from the nasopharynx region, which is where nasal passages meet the back of the throat. To collect a mucus sample, doctors may pass a swab or suction tube deep into the back of the nose. The sample can be tested by culture. It is the most accurate method, but it takes 10 to 14 days to get the results. Polymerase chain reaction (PCR) is often used along with culture to get test results within several days. PCR detects the genetic material (DNA) of whooping cough bacteria.