in the initial regimen Standard precautions should be used for patients with lung abscesses unless tuberculosis is suspected (in which case, airborne precautions should be implemented) Pertussis Pertussis (whooping cough) is caused by Bordetella pertussis or Bordetella parapertussis (the latter being the cause of kennel cough in dogs) There were an estimated 19,000 cases in 2017, with approximately 80% occurring in children (and almost 10% occurring in infants younger than months) A similar clinical syndrome can be caused by adenovirus or Chlamydia trachomatis in infants There are three clinical stages The first symptoms are indistinguishable from a viral URI This catarrhal phase, characterized by a mild cough, conjunctivitis, and coryza, lasts for to weeks An increasingly severe cough heralds the onset of the second stage (paroxysmal), which continues for to weeks After a prolonged spasm of coughing often involving 10 or more coughs in succession, the sudden inflow of air produces the characteristic whoop (young infants lack the ability to generate sufficient negative inspiratory pressure and may, therefore, not whoop) During episodes, children can appear to choke, become cyanotic, and appear anxious Post-tussive emesis is common When not coughing, the child has a remarkably normal history and physical examination, except for an occasional subconjunctival hemorrhage Young infants can exhibit apnea unrelated to coughing paroxysms During the third stage (convalescent), the intensity of the cough wanes At times, pertussis may present as a chronic cough without other signs of infection The fatality rate for pertussis is approximately 1% for patients in the first month of life and 0.3% for those between age and 12 months Complications often occur during the paroxysmal stage The most immediately life-threatening complication is complete obstruction of the airway by a mucous plug, leading to respiratory arrest Secondary bacterial pneumonia occurs in 25% of children with pertussis and accounts for 90% of the fatalities Seizures are seen in 3%, and encephalitis in 1% Sudden increases in intrathoracic pressure can cause intracranial hemorrhages, rupture of the diaphragm, and rectal prolapse The white blood count often is elevated, at times with a leukemoid reaction (the latter more common in infants over months of age) and a lymphocytic predominance Chest radiographs often are normal The diagnosis is by PCR of nasopharyngeal secretions Early treatment can reduce symptoms and shorten the clinical course although it is unclear if antibiotics influence course during paroxysmal phase (does still reduce transmission); however, it is important to start antibiotic treatment when pertussis is suspected and prior to confirmatory testing The preferred treatment is azithromycin (10 mg/kg daily for days in infants