Chapter 3Infectious Diseases Related To Travel
Pneumococcal Disease (<em>Streptococcus pneumoniae</em>)
J. Pekka Nuorti
Pneumococcal disease is caused by the bacterium Streptococcus pneumoniae (pneumococcus), which has more than 91 known serotypes. The major clinical syndromes include life-threatening infections such as meningitis, bacteremia, and pneumonia. Pneumococcus is the most commonly identified cause of community-acquired pneumonia. It is also a major cause of milder but more common illnesses, such as sinusitis and otitis media.
MODE OF TRANSMISSION
S. pneumoniae is transmitted directly from person to person through close contact via respiratory droplets. The organism frequently colonizes the nasopharynx of healthy people, particularly young children, without causing illness. Transmission is thought to be common, but clinical illness occurs infrequently among casual contacts.
Pneumococcal disease occurs worldwide. The reported rates are higher in developing than in industrialized countries. Pneumococcal disease is more common during winter and early spring, when respiratory viruses are circulating. Most illnesses are sporadic. Outbreaks of pneumococcal disease are uncommon but may occur in closed populations, such as nursing homes, childcare centers, or other institutions. In the United States, most deaths from pneumococcal disease occur in older adults, although in developing countries, many children die of pneumococcal pneumonia.
Routine use of the 7-valent pneumococcal conjugate vaccine (PCV7) in the United States since 2000 has dramatically reduced the incidence of pneumococcal disease in both children and adults. Because the vaccine interrupts transmission of vaccine-type pneumococci, rates of pneumococcal disease in unvaccinated older children and adults have also decreased. Many other industrialized countries are also using pneumococcal conjugate vaccines.
The risk for pneumococcal disease is generally highest among young children, the elderly, and people of any age who have chronic medical conditions, such as heart disease, lung disease, diabetes, or asplenia or conditions that suppress the immune system, such as HIV. Cigarette smokers are also at increased risk. While most travelers are not in the high-risk categories, healthy travelers of any age can develop pneumococcal pneumonia while traveling.
Sudden onset of fever and malaise are typical symptoms for all forms of pneumococcal infections and may be the only symptoms in young children with bacteremia. In pneumococcal pneumonia, fever may precede the usual symptoms of cough, pleuritic chest pain, and production of purulent or blood-tinged sputum by 12–24 hours. In elderly people, the onset of pneumococcal pneumonia may be less abrupt, with fever, shortness of breath, or altered mental status as the initial symptoms; sputum production may be absent. Pneumococcal meningitis may present with a stiff neck, headache, lethargy, or seizures.
A definitive diagnosis of pneumococcal infection can be made by isolating the bacterium from blood or other normally sterile body sites, such as cerebrospinal fluid. Most patients with pneumococcal pneumonia, however, do not have detectable bacteremia. The diagnosis of pneumococcal pneumonia can be suspected if, on microscopy, a sputum specimen contains many gram-positive diplococci and polymorphonuclear leukocytes and few epithelial cells. Detection of pneumococcal antigen in urine is a useful diagnostic test for adults.
In pneumococcal pneumonia, typical chest radiography may show lobar, segmental, or multilobar consolidation. Pneumococcal pneumonia is usually, but not always, associated with a high white blood cell count. High white blood cell counts should raise suspicion for this diagnosis, since other serious travel-related diseases causing fever, such as hepatitis, typhoid fever, malaria, dengue fever, or typhus, are all associated with normal or low white blood cell counts.
All types of pneumococcal infections are usually treated with antibiotics. Empiric therapy for suspected pneumococcal infection depends on the syndrome but usually includes a penicillin or cephalosporin. Worldwide, many strains are increasingly resistant to penicillin, cephalosporins, and macrolides, and some are resistant to multiple classes of drugs, complicating treatment choices. Antimicrobial susceptibility of strains isolated from blood and cerebrospinal fluid should be determined, and definitive treatment should be targeted on the basis of susceptibility results.
In 2008, the Clinical and Laboratory Standards Institute adopted new susceptibility breakpoints for penicillin treatment of nonmeningitis cases of pneumococcal disease. However, empiric antibiotic therapy should not be delayed and should begin before microbiologic confirmation. In the United States and other countries where β-lactam resistance among pneumococcal isolates is common, the initial regimen for suspected pneumococcal meningitis should include vancomycin or a fluoroquinolone along with a third-generation cephalosporin, until the antimicrobial susceptibility pattern of the organism is available.
PREVENTIVE MEASURES FOR TRAVELERS
As of 2010, 3 vaccines are available to prevent pneumococcal disease in the United States. These vaccines induce antibodies to the specific types of pneumococcal capsule. No specific recommendations for the use of pneumococcal vaccines in travelers have been formulated.
Pneumococcal Conjugate Vaccines
The 7-valent pneumococcal conjugate vaccine (PCV7) has been part of the routine infant immunization schedule in the United States since 2000. It is recommended for all children aged <5 years. In 2010, a 13-valent pneumococcal conjugate vaccine (PCV13) was approved by the Food and Drug Administration and is replacing PCV7. PCV13 is recommended for routine vaccination of all children aged 2–59 months and for children aged 60–71 months with underlying medical conditions that increase their risk for pneumococcal disease or complications. Children with HIV, sickle cell anemia, asplenia, cerebrospinal fluid leak, or cochlear implant can receive PCV13 through age 18 years. The PCV7 and PCV13 vaccines are recommended as a 4-dose series at ages 2, 4, 6, and 12–15 months. Fewer doses are required for children who begin the series after age 7 months.
Pneumococcal Polysaccharide Vaccine
A 23-valent pneumococcal polysaccharide vaccine (PPSV23) is recommended for all adults aged ≥65 years and for people aged 2–64 years with underlying medical conditions. People with underlying conditions should be vaccinated as soon as possible after the condition is diagnosed. Children with underlying medical conditions that are vaccine indications should also receive PPSV23, after receiving the conjugate vaccine series. Routine revaccination with PPSV23 is not recommended for most people. A second dose is recommended 5 years after the first dose for people with functional or anatomic asplenia and for people with immunocompromising conditions. People ≥65 years who received PPSV23 before age 65 for an underlying medical condition should be administered another dose of PPSV23, if ≥5 years have passed since their previous dose.
The World Health Organization recommends that inclusion of pneumococcal conjugate vaccines in all national immunization programs should be a priority. As of 2008, 26 industrialized countries were routinely using pneumococcal conjugate vaccines, including the United States, Canada, Australia, the United Kingdom, and other Western European and Middle Eastern countries. A 10-valent pneumococcal conjugate vaccine formulation is available in many countries, including Europe, Canada, and Australia.
Vaccine Safety and Adverse Reactions
After receipt of PCV7, mild local reactions such as redness, swelling, or tenderness occur in 10%–23% of infants. Larger areas of redness or swelling or limitations in arm movement may occur in 1%–9% of infants. Low-grade fever can occur in up to 24%, and fever higher than 102.2°F (39°C) may occur in up to 2.5% of vaccinees. The safety profiles of PCV13 and PCV7 are comparable: the most commonly reported (more than 20% of recipients) adverse reactions after PCV13 were injection-site reactions, fever, decreased appetite, irritability, and increased or decreased sleep.
After receipt of PPV23, self-limiting local side effects occur in approximately half of vaccine recipients and are more common after revaccination than after the first dose. These reactions usually resolve within 48 hours. More severe local reactions and systemic symptoms, including myalgias and fever, are rare.
Precautions and Contraindications
PCV7 is contraindicated for children known to have hypersensitivity to any component of the vaccine. PCV13 is contraindicated among people known to have a severe allergic reaction (anaphylaxis) to any component of PCV13 or PCV7 or to any diphtheria toxoid–containing vaccine. Clinicians may delay vaccination of children with moderate or severe illness until the child has recovered, although minor illnesses, such as mild upper respiratory tract infection with or without low-grade fever, are not contraindications to vaccination. Revaccination with PPV23 is contraindicated for people who had a severe reaction (anaphylactic reaction or localized Arthus-type reaction) to the initial dose.
Other Preventive Measures
Chemoprophylaxis is not routinely recommended for travelers or for close contacts of people with pneumococcal meningitis or other cases of invasive disease unless otherwise recommended by the clinician supervising their care.
- American Academy of Pediatrics. Pneumococcal infections. In: Pickering LK, Baker CJ, Kimberlin DW, Long SS, editors. Red Book: 2009 Report of the Committee on Infectious Diseases. 28th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2009. p. 524–35.
- CDC. Licensure of a 13-valent pneumococcal conjugate vaccine (PCV13) and recommendations for use among children—Advisory Committee on Immunization Practices (ACIP), 2010. MMWR Morb Mortal Wkly Rep. 2010 Mar 12;59(9):258–61.
- CDC. Preventing pneumococcal disease among infants and young children. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2000 Oct 6;49(RR-9):1–38.
- CDC. Prevention of pneumococcal disease: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 1997 Apr 4;46(RR-8):1–24.
- Fedson DS, Scott JA. The burden of pneumococcal disease among adults in developed and developing countries: what is and is not known. Vaccine. 1999 Jul 30;17 Suppl 1:S11–8.
- Greenwood B. The epidemiology of pneumococcal infection in children in the developing world. Philos Trans R Soc Lond B Biol Sci. 1999 Apr 29;354(1384):777–85.
- Tunkel AR, Hartman BJ, Kaplan SL, Kaufman BA, Roos KL, Scheld WM, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis. 2004 Nov 1;39(9):1267–84.
- Wikler MA. Performance Standards for Antimicrobial Susceptibility Testing, Eighteenth Informational Supplement. Wayne, PA: Clinical and Laboratory Standards Institute; 2008.
- World Health Organization. Pneumococcal conjugate vaccine for childhood immunisation—WHO position paper. Wkly Epidemiol Rec. 2007;82(12):93–104.
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