whooping cough is a highly contagious bacterial disease. Initially symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough. This is then followed by weeks of severe coughing fits. Following a fit of coughing a high-pitched whoop sound or gasp may occur as the person breathes in. The coughing may last for more than a hundred days or ten weeks. A person may cough so hard they vomit, break ribs, or become very tired from the effort. Children less than one year old may have little or no cough and instead have periods where they do not breathe. The period of time between infection and the onset of symptoms is usually seven to ten days. Disease may occur in those who have been vaccinated but symptoms are typically milder
The classic symptoms of pertussis are a paroxysmal cough, inspiratory whoop and fainting or vomiting after coughing. The cough from pertussis has been documented to cause subconjunctival hemorrhages, rib fractures, urinary incontinence, hernias, and vertebral artery dissection. Violent coughing can cause the pleura to rupture, leading to a pneumothorax. Vomiting after a coughing spell or an inspiratory whooping sound on coughing, almost doubles the likelihood that the illness is pertussis. On the other hand, the absence of a paroxysmal cough or posttussive emesis makes it almost half as likely.
The incubation period is typically seven to ten days with a range of four to 21 days and rarely as long as 42 days, after which there are usually mild respiratory symptoms, mild coughing, sneezing, or runny nose. This is known as the catarrhal stage. After one to two weeks, the coughing classically develops into uncontrollable fits, each with five to ten forceful coughs, followed by a high-pitched "whoop" sound in younger children, or a gasping sound in older children, as the person tries to inhale (paroxysmal stage).
Fits can occur on their own or can be triggered by yawning, stretching, laughing, eating, or yelling; they usually occur in groups, with multiple episodes on an hourly basis throughout the day. This stage usually lasts two to eight weeks, or sometimes longer. A gradual transition then occurs to the convalescent stage, which usually lasts one to two weeks. This stage is marked by a decrease in paroxysms of coughing, both in frequency and severity, and a cessation of vomiting. A tendency to produce the "whooping" sound after coughing may remain for a considerable period after the disease itself has cleared up.
Whooping cough is caused by the bacteria Bordetella pertussis.
The primary method of prevention for pertussis is vaccination. There is insufficient evidence to determine the effectiveness of antibiotics in those who have been exposed but are without symptoms. Preventative antibiotics, however, are still frequently used in those who have been exposed and are at high risk of severe disease (such as infants).
Whooping cough vaccines are effective and are recommended for routine use by the World Health Organization and the Center for Disease Control and Prevention. The vaccine saved over an estimated half a million lives in 2002.
The multi-component acellular pertussis vaccine is 71–85% effective with greater effectiveness for more severe strains. Despite widespread vaccination, however, pertussis has persisted in vaccinated populations and is today "one of the most common vaccine-preventable diseases in Western countries". The twenty-first century resurgences in pertussis infections are attributed to a combination of waning immunity and bacterial mutations that elude vaccines.
Immunization does not confer lifelong immunity; a 2011 CDC study indicated that protection may only last three to six years. This covers childhood, which is the time of greatest exposure and greatest risk of death from pertussis.
Infection induces incomplete natural immunity that wanes over time. Natural immunity lasts longer than vaccine-induced immunity, with one study reporting maximum effectiveness as long as 20 years in the former and 12 in the latter. Vaccination exemption laws appear to increase cases.
A complete blood count is usually ordered. Lymphocytosis is a diagnostic clue for whooping cough, although not specific.
Methods used in laboratory diagnosis include culturing of nasopharyngeal swabs on Bordet-Gengou medium, polymerase chain reaction (PCR), direct immunofluorescence (DFA), and serological methods. The bacteria can be recovered from the person only during the first three weeks of illness, rendering culturing and DFA useless after this period, although PCR may have some limited usefulness for an additional three weeks.
For most adults and adolescents, who often do not seek medical care until several weeks into their illness, serology may be used to determine whether antibody against pertussis toxin or another component of B. pertussis is present at high levels in the blood of the person. By this stage they have been contagious for some weeks and may have spread the infection to many people. Because of this, adults, who are not in great danger from whooping cough, are increasingly being encouraged to be vaccinated.
A similar, milder disease is caused by B. parapertussis.
Common complications include pneumonia, encephalopathy, earache and seizures.
Most healthy older children and adults fully recover, however those with comorbid conditions have a higher risk of morbidity and mortality.
Infection in newborns is particularly severe. Whooping cough is fatal in an estimated 1.6% of hospitalized US infants under one year of age. First year infants are also more likely to develop complications, such as: pneumonia (20%), encephalopathy (0.3%), seizures (1%), failure to thrive and death (1%)—perhaps due to the ability of the bacterium to suppress the immune system. Pertussis can cause severe paroxysm-induced cerebral hypoxia and 50% of infants admitted to hospital suffer apneas. Reported fatalities from pertussis in infants increased substantially from 1990-2010.
The antibiotic erythromycin or azithromycin are typically the recommended treatment. Newer macrolides are frequently recommended due to lower rates of side effects. Trimethoprim-sulfamethoxazole (TMP-SMZ) may be used in those with allergies to first-line agents or in infants who have a risk of pyloric stenosis from macrolides.
A reasonable guideline is to treat people age >1 year within 3 weeks of cough onset and infants age <1 year and pregnant women within 6 weeks of cough onset. If the person is diagnosed late, antibiotics will not alter the course of the illness and, even without antibiotics, they should no longer be spreading pertussis. Antibiotics when used early decrease the duration of infectiousness and thus prevent spread. Short term antibiotics (azithromycin for 3–5 days) are as effective as long-term treatment (erythromycin 10–14 days) in eliminating B. pertussis with less side effects.
People with pertussis are infectious from the beginning of the catarrhal stage (runny nose, sneezing, low-grade fever, symptoms of the common cold) through the third week after the onset of paroxysms (multiple, rapid coughs) or until 5 days after the start of effective antimicrobial treatment.
Effective treatments of the cough associated with this condition have not been developed.