Whooping cough, a condition that results in severe paroxysmal coughing fits followed by a long wheezing inspiratory gasp (the "whoop") is caused by the bacteria Bordetella pertussis. Haemophilus influenzae and Klebsiella pneumoniae both commonly cause pneumonia, and RSV is a virus that is frequently implicated in lower respiratory infections of infants and children.

After the catarrhal stage, an individual with pertussis will progress into the paroxysmal stage. It's during this stage that they will experience uncontrollable fits of 5-15 forceful coughs, followed by a "whoop" or gasp as they struggle to inhale. The force of these coughs can be such that they can result in vomiting, epistaxis, subconjunctival hemorrhage, or even broken ribs. 

The incubation period for pertussis, also known as the catarrhal stage, can last as little as 4 days or as long as 42 days, but a typical period is 1-3 weeks. During this stage the disease looks like a regular upper respiratory infection, with sneezing, mild cough, and runny nose. The infected individual is highly infectious at this time, with bacteria spread by airborne droplets after sneezing or cough. 

The correct answer is "Sarcoidosis." Sarcoidosis is the correct answer as this inflammatory condition is frequently found in African-American women in their 40's who present with fatigue and shortness of breath among other symptoms, who also have erythema nodosum on the lower extremities, and have bilateral hilar infiltrates on chest x-ray. This constellation of findings is highly suggestive of sarcoidosis. Sarcoidosis results in the formation of numerous non-necrotizing granulomas, most commonly found in the lungs, that can play a role in the symptoms experienced by these patients. Other findings suggestive of sarcoidosis include elevated serum calcium levels with normal serum PTH levels.

Tuberculosis can present in a similar manner to sarcoidosis, however given the patient's suburban living environment, lack of a travel history, and lack of healthcare exposure, the likelihood of being exposed to tuberculosis is very low, making sarcoidosis a more likely etiology.

While lung cancer can present as shortness of breath with hilar infiltration in chest x-ray, in a relatively young otherwise healthy patient who also has erythema nodosum and in whom the hilar infiltrates are bilateral, sarcoidosis would be a more likely etiology.

The patient does not have any findings consistent with meningitis (leg rash in meningitis is petechial, not erythema nodosum) or pharyngitis.

Incidence of asthma is lower in populations exposed to an abundance of microbes from a young age. The "hygiene hypothesis" suggests that early immune stimulation by multiple forms of infectious agents may push a Th1 phenotype, reducing the Th2 (allergic) response. 

The most commonly reported triggers for asthma attacks are cold air, emotional stress or excitement, infection, irritants such as pollen or dust mites, and exercise. Other triggers may include lying down, exposure to cigarette smoke, or acid reflux. 

Isoniazid is a bactericidal drug that is given for tuberculosis that has several adverse effects including peripheral neuropathy. This drug is usually administered in conjunction to other antitubercular drugs. Pyridoxine (vitamin B6) is recommended to be taken in conjunction with isoniazid to prevent neurotoxicity.

Isoniazid is relatively inexpensive and may be taken orally or intravenously. It is not necessary to be taken under direct observation, and is usually dosed according to type of disease (active versus latent). The typical duration of administration is roughly 26 weeks. Color blindness is not associated with isoniazid treatment.

Chronic asthma can result in a situation referred to as "airway remodeling," typified by the following changes: increased airway vascularity, epithelial desquamation, deposition of subepithelial collagen, and hypertrophy and hyperplasia of mucus glands and of the underlying muscle layer.

Destruction of alveolar septa and pulmonary capillaries is a common finding in emphysema and does not present in asthma.

Antibiotics have been shown to have very little effectiveness in treating a pertussis infection older than four weeks. Because of this, treatment with antibiotics to individuals that have been symptomatic for longer than four weeks is not generally recommended.

The oxygen concentration should be the lowest possible, due to the risk of oxygen toxicity seen in clients with FIO₂ (fraction of inspired oxygen) levels exceeding 60% for more than 48 hours.