Postexposure management of infectious diseases

INFECTIONS TRANSMITTED BY THE AIRBORNE ROUTE

Airborne transmission of infections occurs by inhalation of droplet nuclei (diameter ≤ 5 μm) generated by coughing and sneezing. Certain procedures (eg, administration of nebulized medication, sputum induction, bronchoscopy) also generate droplets and aerosols, which can transmit organisms.¹

Measles

Measles (Table 3) is highly contagious; up to 90% of susceptible individuals develop measles after exposure. The virus is transmitted by direct contact with infectious droplets and by the airborne route. It remains infectious in the air and on surfaces for up to 2 hours; therefore, any type of exposure, even transient, is an indication for postexposure prophylaxis in susceptible individuals.¹¹

Both the measles, mumps, rubella (MMR) vaccine and immune globulin may prevent or modify disease severity in susceptible exposed individuals if given within 3 days of exposure (for the vaccine) or within 6 days of exposure (for immune globulin).^31,32

Tuberculosis

Mycobacterium tuberculosis is transmitted from patients with pulmonary or laryngeal tuberculosis, particularly if patients cough and are sputum-positive for acid-fast bacilli. Patients with extrapulmonary tuberculosis or latent tuberculosis infection are not infectious.^1,7

Postexposure management of tuberculosis occurs through contact investigation of a newly diagnosed index case of tuberculosis disease. Contacts are categorized as household contacts, close nonhousehold contacts (those having regular, extensive contact with the index case), casual contacts, and transient community contacts. The highest priority for contact investigations should be household contacts, close nonhousehold or casual contacts at high risk of progressing to tuberculosis disease (eg, those with HIV, those on dialysis, or transplant recipients), and unprotected healthcare providers exposed during aerosol-generating procedures.^7,33

Postexposure management includes screening exposed individuals for tuberculosis symptoms and performing tuberculin skin testing or interferon-gamma release assay (blood testing) for those who had previously negative results (Table 3). Chest radiography is recommended for exposed immunocompromised individuals, due to high risk of tuberculosis disease and low sensitivity of skin or blood testing, and for those with a documented history of tuberculosis or previous positive skin or blood test.^7,33,34

A positive tuberculin skin test for persons with recent contact with tuberculosis is defined as a wheal 5 mm or larger on baseline or follow-up screening. Prior bacillus Calmette-Guérin vaccination status should not be used in the interpretation of tuberculin skin testing in the setting of contact investigation.^7,33

All exposed asymptomatic people with a positive result on testing should be treated for latent tuberculosis infection, since treatment reduces the risk of progression to tuberculosis disease by 60% to 90% .^7,33,35–37

Varicella and disseminated herpes zoster

Varicella zoster virus is transmitted by direct contact with vesicular fluid of skin lesions and inhalation of aerosols from vesicular fluid or respiratory tract secretions. Varicella (chickenpox) is highly contagious, with a secondary attack rate in susceptible household contacts of 85%.¹² Herpes zoster is less contagious than varicella.³⁸

Postexposure prophylaxis against varicella is recommended for susceptible individuals who had household exposure, had face-to-face contact with an infectious patient while indoors, or shared the same hospital room with the patient.¹²

Postexposure prophylactic options for varicella and herpes zoster include varicella vaccine (not zoster vaccine) and varicella zoster immune globulin (Table 3).^12,38–40

Varicella vaccine is approximately 90% effective if given within 3 days of exposure, and 70% effective if given within 5 days.^12,39

Antiviral agents should be given if the exposed individual develops manifestations of varicella or herpes zoster.^12,38

INFECTIONS TRANSMITTED BY THE DROPLET ROUTE

Droplet transmission occurs when respiratory droplets carrying infectious agents travel directly across short distances (3–6 feet) from the respiratory tract of the infected to mucosal surfaces of the susceptible exposed individual. Droplets are generated during coughing, sneezing, talking, and aerosol-generating procedures. Indirect contact with droplets can also transmit infection.¹

Group A streptococcal infection

Although group A streptococcal infection (Table 4) may spread to close contacts of the index case and in closed populations (eg, military recruit camps, schools, institutions), secondary cases of invasive group A streptococcal infection rarely occur in family and institutional contacts.^9,41,42

Postexposure prophylaxis for contacts of people with invasive group A streptococcal infection is debated, because it is unknown if antibiotic therapy will decrease the risk of acquiring the infection. It is generally agreed that it should not be routinely given to all contacts. The decision should be based on the clinician’s assessment of each individual’s risk and guidance from the local institution. If indicated, postexposure prophylaxis should be given to household and close contacts, particularly in high-risk groups (eg, Native Americans  and those with risk factors such as old age, HIV infection, diabetes mellitus, heart disease, chickenpox, cancer, systemic corticosteroid therapy, other immunosuppressive medications, intravenous drug use, recent surgery or childbirth).^9,41,42

Influenza

Influenza (Table 4) causes a significant burden in healthcare settings, given its prevalence and potential to cause outbreaks of severe respiratory illness in hospitalized patients and residents of long-term-care facilities.^13,43

Neuraminidase inhibitors are effective as prophylaxis after unprotected exposure to influenza, particularly in outbreak situations. However, their use is not widely recommended, since overuse could lead to antiviral resistance. In selected cases, postexposure prophylaxis may be indicated for close contacts who are at high risk of complications of influenza (eg, age 65 or older, in third trimester of pregnancy or 2 weeks postpartum, morbid obesity, chronic comorbid conditions such as a cardiopulmonary and renal disorder, immunocompromising condition) or who are in close contact with persons at high risk of influenza-related complications.^13,44,45

Meningococcal disease

N meningitidis is transmitted from individuals with meningococcal disease or from asymptomatic carriers.⁸

Postexposure prophylaxis is effective in eradicating N meningiditis and is recommended for all close contacts of patients with invasive meningococcal disease (Table 4).⁴⁶­ Close contacts include household contacts, childcare and preschool contacts, contacts exposed in dormitories or military training centers, those who had direct contact with the index case’s respiratory secretions (eg, intimate kissing, mouth-to-mouth resuscitation, unprotected contact during endotracheal intubation or endotracheal tube management), and passengers seated directly next to an index case on airplane flights of longer than 8 hours.

Postexposure prophylaxis is not indicated for those who had brief contact, those who had contact that did not involve exposure to oral or respiratory secretions, or for close contacts of patients with N meningitidis isolated in nonsterile sites only (eg, oropharynyx, trachea, conjunctiva).^8,46

Pertussis

Pertussis is highly contagious, with a secondary attack rate of approximately 80% in susceptible individuals. Approximately one-third of susceptible household contacts develop pertussis after exposure.¹⁰

Postexposure prophylaxis for pertussis should be given to all household and close contacts (Table 4).^10,47

Rubella

Transmission occurs through droplets or direct contact with nasopharyngeal secretions of an infectious case. Neither MMR vaccine nor immunoglobulin has been shown to prevent rubella in exposed contacts, and they are not recommended.¹¹

INFECTIONS TRANSMITTED BY DIRECT CONTACT

Direct contact transmission includes infectious agents transmitted from an infected or colonized individual to another, whereas indirect contact transmission involves a contaminated intermediate object or person (eg, hands of healthcare providers, electronic thermometers, surgical instruments).¹

There are no available postexposure prophylactic regimens for the organisms most commonly transmitted by this route (eg, methicillin-resistant Staphylococcus aureus, Clostridium difficile), but transmission can be prevented with adherence to standard precautions, including hand hygiene.¹

Hepatitis A

Person-to-person transmission of hepatitis A virus occurs via the fecal-oral route. Common-source outbreaks and sporadic cases can occur from exposure to food or water contaminated with feces.^1,15

Postexposure prophylaxis is indicated only for nonimmune close contacts (eg, household and sexual contacts) (Table 5). Without this treatment, secondary attack rates of 15% to 30% have been reported among households.^15,48 Both hepatitis A vaccine and immune globulin are effective in preventing and ameliorating symptomatic hepatitis A infection. Advantages of vaccination include induction of longer-lasting immunity (at least 2 years), greater ease of administration, and lower cost than immune globulin.^15,48

Scabies

Scabies is an infestation of the skin by the mite Sarcoptes scabiei var hominis. Person-to-person transmission typically occurs through direct, prolonged skin-to-skin contact with an infested person (eg, household and sexual contacts). However, crusted scabies can be transmitted after brief skin-to-skin contact or by exposure to bedding, clothing, or furniture used by the infested person.

All potentially infested persons should be treated concomitantly (Table 5).^14,49

INFECTIONS TRANSMITTED BY MAMMAL BITES AND INJURIES

Bites and injury wounds account for approximately 1% of all visits to emergency departments.⁵⁰ Human bites are associated with a risk of infection by blood-borne pathogens, herpes simplex infection, and bacterial infections (eg, skin and soft-tissue infections, bacteremia). Animal bites are associated with a risk of bacterial infections, rabies, tetanus, hepatitis B virus, and monkeypox.⁵⁰

Rabies

Human rabies (Table 5) is almost always fatal. Essential factors in determining the need for postexposure prophylaxis include knowledge of the epidemiology of animal rabies in the area where the contact occurred and the species of animal involved, availability of the animal for observation or rabies testing, health status of the biting animal, and vaccination history of both the animal and exposed individual.⁶ Clinicians should seek assistance from public health officials for evaluating exposures and determining the need for postexposure prophylaxis in situations that are not routine.⁵¹

High-risk wild animals associated with rabies in North America include bats, raccoons, skunks, foxes, coyotes, bobcats, and woodchucks. Bats are the most common source of human rabies infections in the United States, and transmission can occur from minor, sometimes unnoticed, bites. The types of exposures that require postexposure prophylaxis include bites, abrasions, scratches, and contamination of mucous membranes or open wound with saliva or neural tissue of a suspected rabid animal.

Human-to-human transmission of rabies can rarely occur through exposure of mucous membrane or nonintact skin to an infectious material (saliva, tears, neural tissue), in addition to organ transplantation.⁶

Animal capture and testing is a strategy for excluding rabies risk and reducing the need for postexposure prophylaxis. A dog, cat, or ferret that bites a person should be confined and observed for 10 days without administering postexposure prophylaxis for rabies, unless the bite or exposure is on the face or neck, in which case this treatment should be given immediately.⁶ If the observed biting animal lives and remains healthy, postexposure prophylaxis is not recommended. However, if signs suggestive of rabies develop, postexposure prophylaxis should be given and the animal should be euthanized, with testing of brain tissue for rabies virus. Postexposure prophylaxis should be discontinued if rabies testing is negative.

The combination of rabies vaccine and human rabies immunoglobulin is nearly 100% effective in preventing rabies if administered in a timely and accurate fashion after exposure (Table 5).⁶

Tetanus

Tetanus transmission can occur through injuries ranging from small cuts to severe trauma and through contact with contaminated objects (eg, bites, nails, needles, splinters, neonates whose umbilical cord is cut with contaminated surgical instruments, and during circumcision or piercing with contaminated instruments).⁵

Tetanus is almost completely preventable with vaccination, and timely administration of postexposure prophylaxis (tetanus toxoid-containing vaccine, tetanus immune globulin) decreases disease severity (Table 5).^2,5,52