Preventing Exposure to Opportunistic and Other Infections


Persons with HIV infection are more susceptible than others to certain infections. HIV-infected persons may come into contact with opportunistic pathogens in the course of various aspects of their daily activities. Pets, children, personal and sexual contacts, and food and water, as well as involvement in occupational tasks, recreation, hobbies, and other activities all potentially can expose an HIV-infected person to opportunistic pathogens, some of which are ubiquitous and cannot be avoided. Among the ubiquitous pathogens are Candida, Mycobacterium avium, Pneumocystis jiroveci, and human herpesvirus 6 and 7. Exposure to other opportunistic pathogens may be minimized if patients are aware of the risks.

The following tables group opportunistic pathogens by type of exposure. Mechanisms of transmission and recommendations for avoidance are outlined. Note that a number of infections can be transmitted by several of these modes.

For information about vaccinations, see chapter Immunizations for HIV-Infected Adults and Adolescents; for opportunistic infection (OI) prophylaxis, see chapter Opportunistic Infection Prophylaxis.


Water Related
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • Hepatitis A virus (HAV)
  • Cryptosporidium
  • Shigella
  • Campylobacter
  • Amoeba
  • Giardia
  • Isospora
  • Microsporidia
  • Infection occurs through drinking contaminated water or eating produce or other food that has been washed in contaminated water.
  • Water ingested accidentally during recreation also can make people sick.
Recommended avoidance measures
  • To decrease exposure from water in developing countries, take the following precautions:
  • Do not drink tap water or use it to brush teeth.
  • Avoid ice that is not made from bottled water.
  • Avoid raw fruits or vegetables, as they may have been washed in tap water.
  • Bring tap water to a rolling boil for at least 1 minute before consuming. If this is not possible, treatment with iodine or chlorine, especially in conjunction with filtering, reduces risk of infection.
  • Additional recommendations, include the following:
  • Avoid drinking untreated water.
  • When choosing a home water filter, especially for filtering untreated water, be aware that not all filters remove the pathogens listed above.
  • Do not drink water from lakes or rivers.
  • Avoid swimming in water that may be contaminated with stool.
  • Avoid swallowing water during recreational activities (lakes, rivers, saltwater beaches, pools, hot tubs, and ornamental fountains may be contaminated with Cryptosporidium).
  • In the event of a cryptosporidiosis outbreak in the municipal water supply, boil tap water for at least 1 minute to eliminate risk of infection.
  • Cryptosporidium may be present in municipal water outside outbreak settings, though the magnitude of this risk is unknown. Some HIV-infected patients may choose to take precautions to decrease risk.
  • Be aware that bottled water may be contaminated with Cryptosporidium.
  • See the discussion of travel-related topics, below.
Food Associated
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • Toxoplasma
  • Salmonella, Shigella, Campylobacter (enteric infections)
  • Listeria
  • Cryptosporidium
  • Other enteric pathogens
  • Exposure may occur through eating or handling contaminated food.
Recommended avoidance measures
  • Always wash hands before preparing and consuming food.
  • Wash hands, cutting boards, counters, and utensils thoroughly after contact with uncooked foods.
  • Do not allow raw meat or eggs to come into contact with other foods.
  • Wash produce thoroughly.
  • Cook meat and poultry to an internal temperature of 165-170°F. It is safest to confirm temperature with a thermometer. Meat that is no longer pink inside likely has reached a temperature of 165°F.
  • Avoid raw or unpasteurized milk, including goat milk, and foods that contain unpasteurized milk or milk products.
  • Avoid foods that might contain raw egg (e.g., Hollandaise sauce, Caesar salad dressing, some mayonnaises, uncooked cake and cookie batter, eggnog, homemade ice cream). Pasteurized eggs can be used safely in recipes that call for raw egg.
  • Avoid eating raw or lightly steamed shellfish.
  • Avoid eating raw seed sprouts, as these may be contaminated with enteric pathogens.
  • Avoid foods from street vendors, especially in developing countries.
  • Be aware that unpasteurized juices may be contaminated with Cryptosporidium.
  • Rates of infection with Listeria are low, but HIV-infected people who are severely immunocompromised are at increased risk.
  • HIV-infected persons who wish to decrease their risk of listeriosis should take the following precautions:
  • Avoid soft cheeses including feta, brie, camembert, blue-veined, and Mexican-style cheeses such as queso fresco unless they are clearly labeled as pasteurized. Hard cheeses, processed cheeses, cream cheese, cottage cheese, and yogurt generally are safe.
  • Before eating leftover foods or ready-to-eat foods, such as hot dogs, cook them until they are steaming hot.
  • Avoid foods from deli counters, such as prepared meats, salads, and cheeses, or heat these foods until steaming hot before eating them.
  • Avoid refrigerated pâté, or heat until steaming hot. Canned or shelf-stable pâté generally is safe.
  • Avoid refrigerated smoked seafood, unless it is part of a cooked dish. Canned or shelf-stable smoked seafood generally is safe.
  • Also see information on travel-related infections, below.
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • Toxoplasma gondii
  • Cryptosporidium
  • Coccidioides
  • Histoplasma capsulatum
  • Cryptococcus neoformans
  • Aspergillus
  • Cryptosporidium and Toxoplasma may be present in soil and sands, and infection can occur through handling soil during gardening or playing in or cleaning sandboxes.
  • Infection with Coccidioides and Histoplasma occurs with inhalation of fungal spores that become airborne owing to disturbance of contaminated soil.
Recommended avoidance measures
  • Wash hands thoroughly after contact with soil or sand.
  • Endemic fungi cannot be completely avoided in certain geographic areas; however, avoiding high-risk activities can decrease risk of infection.
  • In endemic coccidioidomycosis areas, avoid exposure to soil disturbance such as that which occurs during dust storms and at excavation and construction sites.
  • Risk of Aspergillus infection also may be decreased by avoidance of dusty environments.
  • Patients with CD4 counts of <150 cells/µL should avoid activities that put them at increased risk of exposure to Histoplasma in endemic areas, such as:
  • Cleaning, remodeling, or demolishing old buildings
  • Disturbing soil beneath bird roosting sites
  • Cave exploration
  • Other contact with bird or bat droppings
  • Limiting exposure to bird droppings may decrease risk of infection with C. neoformans.
Respiratory and Bodily Contact
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • Mycobacterium tuberculosis
  • Enteric pathogens
  • Influenza
  • Varicella-zoster virus (VZV)
  • Tuberculosis (TB) is transmitted when a person with pulmonary or laryngeal TB coughs, sneezes, shouts, or sings, generating infected droplets that are inhaled by a susceptible person.
  • HIV-infected persons working or residing in certain environments, such as hospitals, nursing homes, homeless shelters, and correctional institutions, may become exposed to TB.
  • Influenza virus is spread by exposure to infected respiratory droplets or contaminated surfaces.
  • VZV is transmitted through contact with aerosolized respiratory droplets or by contact with skin lesions.
  • Many respiratory and enteric pathogens may be spread by contact with contaminated fomites.
Recommended avoidance measures
  • HIV-infected persons should be aware of the increased risk of TB infection associated with certain environments. The following measures decrease risk of infection:
  • In settings with a high risk of TB transmission, patients with known or suspected TB should be physically separated from others.
  • All HIV-infected persons should be tested for latent TB infection.
  • All HIV-infected patients with latent TB infection (LTBI) should receive a complete course of LTBI treatment.
  • HIV-infected persons with a history of significant TB exposure should be treated presumptively for LTBI regardless of the results of LTBI testing, once active infection has been ruled out.
  • Bacillus Calmette-Guérin (BCG) vaccination is not recommended in the United States, and it is contraindicated for HIV-infected persons.
  • People susceptible to VZV should avoid persons with active chickenpox or herpes zoster (shingles).
  • VZV-susceptible, HIV-negative household contacts should be vaccinated against VZV, so that they will not transmit VZV to their HIV-infected contact.
  • Frequent handwashing can reduce risk of diarrhea in HIV-infected persons.
Associated with Sexual Contact
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • HIV
  • Hepatitis B virus (HBV)
  • Hepatitis C virus (HCV)
  • Hepatitis A virus (HAV)
  • Human papillomavirus (HPV)
  • Cytomegalovirus (CMV)
  • Herpes simplex virus (HSV)
  • Syphilis
  • Chlamydia
  • Gonorrhea
  • Trichomonas
  • Lymphogranuloma venereum (LGV) serovars of Chlamydia trachomatis
  • Cryptosporidium
  • Shigella
  • Campylobacter
  • Amoeba
  • Giardia
  • Isospora
  • Microsporidia
  • Depending on the pathogen, infection may be transmitted by exchange of body fluids, by skin-skin contact, or by oral-fecal contact.
  • Sexually transmitted diseases (STDs) can occur at genitals, rectum, or mouth, depending on sexual practices.
  • A number of enteric pathogens can be transmitted during sex (by oral-fecal contact).
Recommended avoidance measures
  • Male latex condoms, when used consistently and correctly:
  • Are highly effective in preventing sexual transmission of HIV and many other STDs, including syphilis, chlamydia, gonorrhea, and trichomoniasis.
  • Decrease risk of acquiring HSV-2, HPV, CMV, HBV, and HCV.
  • Do not prevent enteric pathogen exposure (which is via fecal-oral contact).
  • HIV-infected persons should be screened for STDs at least annually. Those with multiple partners or high-risk partners or sexual practices should be screened more frequently.
  • To avoid infection with HSV, HIV-infected persons should avoid sexual contact when a partner has an overt herpetic lesion (genital or oral-labial), though HSV transmission also can occur during asymptomatic shedding. Consistent use of male condoms also has been shown to reduce HSV transmission risk in heterosexual couples.
  • The use of suppressive antiviral therapy by persons with genital herpes reduces HSV-2 transmission to susceptible partners, though the effectiveness of this approach in HIV-infected patients has not been evaluated.
  • Patients who are CMV seronegative should be advised that CMV can be sexually transmitted.
  • To decrease risk of exposure to enteric pathogens during sex, patients can:
  • Use barriers such as dental dams during oral-anal contact.
  • Change condoms after anal sex.
  • Wear latex gloves during digital-anal contact.
  • Wash hands after sex.
Injection Drug Use Associated
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • HIV
  • HCV
  • HBV
  • CMV
  • Staphylococcus aureus, including MRSA
  • Pseudomonas aeruginosa
  • Streptococcus
  • Clostridium
  • Enteric bacteria and oral anaerobes
  • Leishmania
  • Fungi
  • Injection drug users are at risk of a host of infections, including viral hepatitis, skin and soft-tissue infections, infective endocarditis, and pulmonary infections.
  • Injection drug use also may put users at risk of acquiring TB and STDs.
  • Infection may occur from contaminated drug-injection equipment (needles, syringes, water, and other preparation equipment).
  • Infection also may occur from the user's own skin or mouth bacteria, which can enter the bloodstream.
  • The drug itself, or an adulterating substance, may be contaminated.
Recommended avoidance measures
  • Injection drug users should be advised not to share needles or drug preparation equipment, and should be educated about needle exchange programs.
  • If receptive, injection drug users should be referred to substance abuse treatment programs.
  • Injection drug users should be educated about methods of reducing risk, including the following:
  • If equipment is being reused, clean with bleach and water.
  • Avoid dangerous injection sites such as groin and neck.
  • Do not crush capsules or tablets in the mouth prior to injecting, as this may introduce harmful oral bacteria into the bloodstream.
  • Do not lick injection needles or syringes.
  • Use boiled water for preparing drugs for injection; if not available, use tap water.
  • Boil the drug before injecting.
  • Use a new or disinfected "cooker," and a new filter to prepare drugs for injection.
  • Always clean injection sites with alcohol before injecting.
  • Be aware that black tar heroin may be contaminated with Clostridium spores, which are not killed by heating the drug prior to use.
Other Bloodborne Related
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • HIV
  • HCV
  • HBV
  • CMV
  • Tattooing and body piercing.
  • Reuse of medical equipment and transfusion of infected blood (primarily outside the United States).
  • Occupational exposures (e.g., needlesticks) of health care workers.
Recommended avoidance measures
  • Persons considering tattooing or piercing should be educated about the potential risk of bloodborne pathogen transmission if proper infection control procedures are not followed.
  • When receiving a transfusion, HIV-infected patients who are seronegative for CMV should be administered only CMV antibody-negative or leukocyte-reduced cellular blood products in nonemergency situations.
  • Universal precautions always should be followed by health care workers.
Pet and Animal Related
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • Toxoplasma
  • Cryptosporidium
  • Salmonella
  • Campylobacter
  • Shiga toxin-producing Escherichia coli
  • Bartonella
  • Leptospira
  • Brucella
  • Capnocytophaga
  • Cryptococcus
  • Mycobacterium avium and marinum
  • H. capsulatum
  • For the most part, people with HIV infection can and should keep their pets.
  • HIV-infected persons should be made aware of the potential risks posed by animals and of the avoidance measures for decreasing risks of infection.
  • Exposure may occur though a lick, a bite, or a scratch, or through contact with a pet's stool. Some infections may be spread though contact with an animal's coat or skin.
  • Fleas may spread some infections to pet owners.
  • Patients also may be exposed while performing occupational tasks that bring them into contact with animals (e.g., in pet stores, veterinary clinics, farms, and slaughterhouses).
Recommended avoidance measures
  • Always wash hands after handling animals, and after cleaning cages or aquariums.
  • When acquiring a new pet, avoid animals <6 months of age (cats younger than 1 year) and those with diarrhea.
  • Stray animals may carry many infections and should be avoided.
  • Avoid contact with animal stool.
  • Avoid animals with diarrhea.
  • Pets with diarrhea should be examined by a veterinarian and should have stool checked for Cryptosporidium, Salmonella, Campylobacter, and Shiga toxin-producing E. coli.
  • Wash any bites or scratches with soap and water, and seek medical attention.
  • Animals should not be allowed to lick people in the mouth, or on any open cuts or wounds.
  • Cats may increase risk of Toxoplasma and Bartonella infection.
  • To minimize risk of Toxoplasma exposure:
  • Litter boxes should be cleaned daily, preferably by someone who is not HIV infected or pregnant.
  • If an HIV-infected person is cleaning a litter box, gloves should be used, and hands should be washed afterward.
  • Keep cats indoors and do not allow them to hunt.
  • Do not feed cats raw or undercooked meat.
  • In areas where histoplasmosis is endemic, avoid contact with bird droppings, including soil under bird roosting sites.
  • Always use gloves when cleaning aquariums to avoid contact with Mycobacterium marinum .
  • Avoid contact with reptiles (such as lizards, snakes, and turtles), as well as chicks and ducklings, as these may carry Salmonella.
  • Avoid exotic pets such as monkeys, ferrets, and other wild animals.
Contact with Children
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • CMV
  • Cryptosporidium
  • Giardia
  • HAV
  • Influenza
  • VZV
  • Enteric pathogens
  • HIV-infected persons who work as childcare providers, or who have children in daycare, may be exposed to opportunistic pathogens.
  • The poor personal hygiene habits of children facilitate spread of infection.
  • Risks specific to the individual, given his/her immune status and medical history, should be discussed with a health care provider.
  • CMV infection may occur through contact with many body fluids, including stool, urine, and saliva.
  • Diapering may bring a person into contact with Cryptosporidium and other enteric pathogens.
  • In addition to opportunistic pathogens, childcare providers are exposed to other illnesses, carried by children, to which they may be more susceptible.
Recommended avoidance measures
  • Wash hands thoroughly after contact with stool or urine.
  • Wash hands after diapering and disinfect changing station often.
  • Wash hands after contact with saliva or objects covered with saliva, such as cups or pacifiers.
  • Ensure that the immunization status of HIV-infected persons is up to date, as appropriate for their immune status.
  • HIV-infected persons who are susceptible to VZV should avoid exposure to people with chickenpox or shingles.
  • VZV-susceptible household contacts of HIV-infected persons should be vaccinated against VZV if they are HIV negative, so that they will not transmit VZV to their HIV-infected contact.
Travel Related
Mechanisms of TransmissionDetails and Recommendations for Avoidance
  • Enteric pathogens
  • Plasmodium species (malaria)
  • Yellow fever virus
  • Dengue virus
  • Other geographically specific infections
  • Travelers to developing countries are at risk of foodborne and waterborne infections.
  • Malaria is transmitted by the bite of an infected female Anopheles mosquito.
  • HIV-infected patients are at higher risk of severe malaria.
  • Yellow fever and dengue fever are spread by mosquito bites.
Recommended avoidance measures
  • Plan the travel itinerary, vaccinations, and prophylaxis in consultation with a health care provider experienced in travel medicine.
  • Discuss area-specific risks and avoidance measures with the health care provider.
  • The U.S. Centers for Disease Control and Prevention (CDC) Traveler's Health website has detailed information on most issues pertaining to infections in travelers (
  • Review and update routine vaccination history prior to travel.
  • Generally, live vaccines for HIV-infected persons should be avoided, with some exceptions:
  • Measles vaccination is recommended for all nonimmune persons with CD4 counts of ≥200 cells/µL. Measles immune globulin should be considered for those with CD4 counts of <200 cells/µL who are traveling in measles-endemic areas.
  • Varicella vaccination can be considered for VZV-seronegative persons with CD4 counts of ≥200 cells/µL.
  • Yellow fever vaccination may be considered, see below.
  • Inactivated (killed) enhanced-potency polio and typhoid vaccines should be given instead of the live, attenuated forms.
  • Killed and recombinant vaccines including influenza, diphtheria-tetanus, rabies, HAV, HBV, Japanese encephalitis, and meningococcal vaccines should be administered as they would be for HIV-uninfected persons preparing for travel.
  • The oral cholera vaccine (not available in the United States) is not recommended for most travelers by the CDC.

Traveler's diarrhea:

  • See sections on foodborne and waterborne infections (above) for risk-reduction strategies.
  • Antimicrobial prophylaxis is not routinely recommended for HIV-infected persons traveling in developing countries.
  • Prophylaxis may be appropriate in select situations (for example, high risk of infection and short length of travel).
  • For those to whom prophylaxis is given, fluoroquinolones (such as ciprofloxacin 500 mg PO QD) may be considered for nonpregnant patients.
  • HIV-infected patients traveling in developing countries should bring antibiotics to be used empirically in the event of developing diarrhea.
  • Appropriate regimens include:
  • Ciprofloxacin 500 mg PO BID for 3-7 days
  • Azithromycin 500 mg PO QD as an alternative, and for pregnant women
  • Antiperistaltic agents such as loperamide or diphenoxylate can be useful in the treatment of traveler's diarrhea.
  • Do not use antiperistaltic agents if high fever or blood in the stool is present. Stop use if symptoms persist >48 hours.
  • Seek medical care if diarrhea is severe, bloody, accompanied by fever and chills, leads to dehydration, or does not respond to empiric therapy.
Recommended avoidance measures


  • HIV-infected patients should be advised to avoid travel in malarious areas.
  • If travel to a malarious area cannot be avoided, effective chemoprophylaxis should be given. Consult the CDC Traveler's Health website ( for specific information.
  • Be aware that some malaria prophylaxis medications may have drug-drug interactions with antiretrovirals.
  • Personal protection measures should be followed, including avoidance of peak biting times and use of insect repellants, protective clothing, and permethrin-soaked bed netting.

Yellow fever:

  • HIV-infected patients should be discouraged from visiting areas where yellow fever infection is a risk.
  • Vaccination may be considered in some HIV-infected persons with high CD4 counts who cannot avoid potential exposure, after discussion of risks and benefits.
  • Vaccine response may be poor, and serologic testing can be considered.
  • If vaccination is not administered, patients should be advised about the risk of yellow fever, instructed about avoiding the bites of vector mosquitoes, and provided with a vaccination waiver letter.
  • Personal protection measures should be followed, including avoidance of peak biting times and use of insect repellants, protective clothing, and permethrin-soaked bed netting.

Other geographically specific opportunistic infections include visceral leishmaniasis, Penicillium marneffei infection, coccidiomycosis, histoplasmosis, and TB.