Infectious Disease and the Athlete
Mark D. Harris
Thomas M. Howard
Sports participation has increased 7% in the United States since 1999 (44).
Many athletes and providers associate sports medicine with orthopedic injuries, but up to 50% of visits to high school and college training rooms are for infectious diseases (41).
Seventy-six percent of Masters athletes in one study perceived themselves to be less vulnerable than their sedentary peers to viral illnesses (55).
Many studies suggest a drop in upper respiratory tract infection (URTI) incidence in moderate exercisers compared to sedentary people (11,33,34), some by as much as 20%-30% (40).
Special needs athletes have fewer infections than nonathletes with similar needs (25).
IMMUNOLOGY AND EXERCISE
The immune system includes the innate immune system, which provides nonspecific but immediate response to a wide variety of pathogens, and the acquired immune system, which provides delayed-onset but precisely targeted immunity (1).
The innate immune system includes infection-fighting cells such as natural killer (NK) cells, phagocytes (neutrophils, monocytes, and macrophages), tumor necrosis factor, other cytokines, and complement factors (1). It includes barriers such as the skin, mucous membranes, and nasal hairs. Areas of turbulent airflow, temperature and pH, and pathogen and debris removal systems, such as the gastrointestinal tract and the mucociliary elevator, are also important parts of the innate immune system (7). Barriers can be breeched by environmental conditions, such as sun, wind, humidity, temperature, and trauma.
The acquired immune system is composed of B and T lymphocytes, the immunoglobulins (Ig) that they produce, and cytokines that regulate the immune response (1). Secretory IgA in mucus is an especially important early defense (30).
Nasal breathing allows moderate volumes of air to be warmed, hydrated, and filtered by the nasal mucosa, hairs, and turbulent air flow. This removes harmful particles for disposal via expectoration, sneezing, coughing, or gastrointestinal elimination (8).
During strenuous exercise, the body’s requirement for oxygen increases and the athlete transitions from nose breathing to mouth breathing. This brings in greater volumes of air but overloads or bypasses the warming and filtering mechanisms. Colder and drier air thickens the mucus and disrupts the mucociliary elevator while absence of filtering causes more foreign particles to be deposited in the lower airways (8). The ability of airways to remove them is also diminished, and airway inflammation is a common result (5).
Moderate exercise, defined as exercise for 5-60 minutes within a range of 40%-60% of maximum heart rate (MHR), improves many aspects of immunity. Neutrophil and NK cell counts and salivary IgA increase with moderate exercise (7,8,30,45,46).
Intense exercise, defined as 5-60 min of exercise at 70%-80% of MHR, and prolonged exercise, often defined as greater than 60 minutes, can have detrimental effects on the immune system (7). Cellular immunity is impaired because cortisol and adrenaline concentrations chronically increase (9). Immunomodulators prolactin and growth hormone also increase, but the result is less clear. The function of lymphocytes and B cells decreases, as do neutrophil counts. CD4-CD8 T-cell ratios are normally about 1.5:1 but decrease after intense or long-duration exercise, diminishing immune effectiveness (8). Prolonged, intense exercise causes NK cell number concentrations to fall (41). Salivary lactoferrin and lysozyme concentrations fall (62). Serum neutrophil levels decline (64), and nasal and salivary IgA concentrations fall (47), as do serum IgG and IgE concentrations (42).
INFECTIONS AND EXERCISE
Infections can compromise athletes’ ability to perform (8). Fever impairs coordination, concentration, muscle strength, and aerobic power (41). It also hinders fluid and temperature regulation and endurance. Viral illnesses contribute to tissue wasting, muscle catabolism, and negative nitrogen balance (41).
Drugs commonly used to treat symptoms of infectious disease can also affect athletes. Acetaminophen is generally safe, but antibiotics can cause diarrhea, and quinolones may be associated with tendon rupture. Antihistamines can cause sedation, and usage of ephedrine-containing compounds, banned by many sports organizations, will lead to positive
drug tests and disqualification of an athlete during the competitive season (31,41).
Fever can be treated with acetaminophen (up to 4 g per day divided into doses every 4-6 hrs) or nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or indomethacin. In dehydrated patients, NSAIDs may contribute to renal insufficiency.
RHINORRHEA AND NASAL CONGESTION
Upper Respiratory Tract Infections
Adults usually get one to six URTIs per year, and athletes are no exception, with URTIs predominating even at Olympic competition (24). They are generally viral and are transmitted by direct contact, usually hand to nose, eyes, or mouth. Transmission occasionally occurs via small-particle aerosols and large-particle droplets. Rhinovirus (10%-40%), coronavirus (20%), and respiratory syncytial virus (10%) are the most common causes (49). In closed communities, such as locker rooms, one index patient can infect 25%-70% of exposed teammates (49).
URTI diagnosis is clinical, with symptoms including nasal congestion, sore throat, cough, and fatigue (56). Physical findings include rhinorrhea with boggy nasal mucosa and oropharyngeal erythema. Fever greater than 100.4°F is unusual (24). The incubation period is usually 1-3 days, and symptoms usually last 3-7 days. Complications include bacterial sinusitis (2.5%), asthma exacerbations (up to 40%), and lower respiratory infections (49).
Treatment is symptomatic, including fluids, nonnarcotic pain control, and decongestants or antihistamines as needed. Saline nose rinses can improve symptoms (53). If the URTI can be traced to a specific pathogen, such as influenza, antivirals, such as oseltamivir, can be useful (9).
Handwashing with soap and water or use of alcohol-based hand sanitizers minimizes transmission. Good nutrition, moderate exercise, good hydration, and adequate sleep contribute to good health. Symptomatic individuals should cough or sneeze on their sleeve, not on their hand, and avoid public gatherings when possible (www.cdc.gov/flu/protect/covercough.htm).
Influenza vaccine has an efficacy of 70%-90% in the under 65 population, so every athlete should get immunized annually (38). One study suggested that exercise might improve response to influenza immunization (17).
The “neck check” described later is a good rule of thumb to decide when to send an athlete back to play.
Sinusitis is inflammation of the paranasal sinuses, especially the maxillary and frontal sinuses. It is usually viral and self-limited and is a common complication of URTI, affecting 16% of U.S. adults annually (49).
Bacterial sinusitis can be caused by Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Staphylococcus aureus, and other less common bacteria. Seventy-five percent of cases of bacterial sinusitis will spontaneously resolve within 1 month (49). Swimmers, divers, water polo players, and surfers seem to be more likely to develop sinusitis (41).
Fever, purulent nasal discharge, maxillary toothache, sinus pain, and sinus tenderness to palpation suggest a bacterial cause (8,28). Patients who develop a URTI and improve for several days and then abruptly worsen again are more likely to have a bacterial sinus infection (24).
The Berg Prediction Rule considers purulent rhinorrhea and sinus pain, unilateral and bilateral, in determining the likelihood of bacterial sinusitis (54).
Bacterial sinusitis is best treated with antibiotics, such as amoxicillin or trimethoprim-sulfamethoxazole (28). Second-line agents include doxycycline, clarithromycin, or amoxicillin clavulanate. The standard course is 10-14 days, but some studies suggest that a 3-day course is sufficient (41). Treatment of viral sinusitis is symptomatic, similar to that for URTI, but saline nasal spray can dilute thick mucus and provide short-term relief (53).
The “neck check” is a useful return-to-play guideline for sinusitis.
Acute bronchitis is characterized by inflammation of the bronchial tree with cough lasting up to 3 weeks, with or without sputum production, in the presence of URTI (2). More than 10 million office visits per year are diagnosed as acute bronchitis (36). The same viruses that cause URTI cause 90% of acute bronchitis cases, and the last 10% generally involve bacteria such as Bordetella pertussis, Mycoplasma pneumoniae, and Chlamydia pneumoniae (36). Patients with bronchitis complain of cough as the dominant symptom. Fever can be present but more likely represents influenza or pneumonia.
Treatment is symptomatic, and antibiotics are rarely indicated. Bronchodilators may be useful to improve respiratory flow dynamics, which are often temporarily impaired (2), especially in patients with exercise-induced bronchospasm or asthma (35). Antitussive medications lack proof of effectiveness (2).
Return to play can be complicated by postbronchitic airway inflammation. Inhaled steroids or bronchodilators may be helpful.
Pneumonia is a lower respiratory tract infection caused by viruses in 30%-50% of cases and by bacteria in the rest of cases in healthy adults (41). Community-acquired pneumonia affects about 12 people per 1,000 population per year (37),
and fever, productive cough, malaise, anorexia and myalgias are common complaints. In severe cases, patients may show tachypnea, nasal flaring, intercostal and neck retractions, rales, abnormal pulse oximetry, and cyanosis. Chest x-ray (CXR) may show infiltrates, and complete blood count (CBC) may show leukocytosis with a left shift (36).
Clinical prediction tools such as the Pneumonia severity index (PSI) or PORT score and the CURB-65/CRB-65 can help clinicians decide on inpatient or outpatient therapy (16). The PSI/PORT score predicts severity based on the patient’s demographics, comorbidities, examinations, and laboratory or radiologic findings. The CURB-65/CRB-65 predicts severity based on the patient’s mental status, blood urea nitrogen, respiratory rate, blood pressure, and age.
Macrolides are the first choice for oral outpatient therapy. Patients with more severe disease should be hospitalized; however, even in the inpatient setting, intravenous antibiotics did not outperform oral antibiotics in patients without life-threatening illness (37). Both influenza and pneumococcal vaccines decreased the incidence of pneumonia in immunocompetent people, especially the elderly, in several studies (37).
Athletes should be on strict rest while symptomatic and very gradually return to play thereafter.
Viruses that cause URTI cause the majority of cases of pharyngitis. Symptoms and treatment are similar to those for URTI. Other infectious causes include Epstein-Barr virus (EBV), herpes simplex virus (HSV), group A beta-hemolytic streptococci (GABHS), and rarely, Mycoplasma and gonococcus (10,29).
History should include time of onset, ill contacts, presence of URTI symptoms, throat pain, and difficulty swallowing or speaking.
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