HIV is most commonly transmitted to children by

In young children, HIV infection is nearly always acquired from the mother. More than 90% of HIV-infected children in the United States acquired the infection from their mother, either before or around the time of birth (called vertical transmission or mother-to-child transmission). Most of the remaining children now living with AIDS acquired the infection from sexual activity, including, rarely, sexual abuse. Because of improved safety measures regarding screening of blood and blood products, in recent years almost no infections have resulted from the use of blood and blood products in the United States, Canada, or Western Europe.

As many as 7,000 HIV-infected women give birth each year in the United States. Without preventive measures, 25 to 33% of them would transmit the infection to their baby. The risk of transmission is highest among mothers who acquire HIV infection during pregnancy or while breastfeeding, who are severely ill, or who have more virus in their body. Transmission often takes place during labor and delivery. However, transmission has declined significantly in the United States from about 25% in 1991 to 1% in 2009. Mother-to-child transmission has been reduced because of an intensive effort to test and treat infected pregnant women during both pregnancy and delivery.

The virus also can be transmitted in breast milk. About 12 to 14% of infants not infected at birth acquire HIV infection if they breastfeed from an HIV-infected mother. Most often, transmission occurs in the first few weeks or months of life but may occur later. Transmission by breastfeeding is more likely in mothers who have a high level of virus in their body, including those who acquired the infection during the time period in which they were breastfeeding their infant.

In adolescents, transmission is the same as in adults (see Through sexual activity):

Heterosexual and homosexual adolescents are at increased risk of HIV infection if they have unprotected sex. Adolescents who share infected needles while injecting drugs are also at increased risk.

In very rare cases, HIV has been transmitted by contact with infected blood on the skin. In almost all such cases, the skin surface was broken by scrapes or open sores. Although saliva may contain the virus, transmission of infection by coughing, kissing, or biting has never been confirmed.

HIV is not transmitted through

Common symptoms of HIV infection in untreated children include

Sometimes children have repeated episodes of bacterial infections, such as a middle ear infection (otitis media), sinusitis, bacteria in the blood (bacteremia), or pneumonia.

A variety of symptoms and complications can appear as the child's immune system deteriorates. About one third of HIV-infected children develop lung inflammation (lymphoid interstitial pneumonitis), with cough and difficulty breathing.

Children born with HIV infection commonly have at least one episode of Pneumocystis jirovecii pneumonia (see Pneumonia in Immunocompromised People). This serious opportunistic infection can occur as early as 4 to 6 weeks of age but occurs mostly in infants 3 to 6 months of age who acquired HIV infection before or at birth. More than half of untreated children infected with HIV develop the pneumonia at some time. Pneumocystis pneumonia is a major cause of death among children and adults with AIDS.

In a significant number of HIV-infected children, progressive brain damage prevents or delays developmental milestones, such as walking and talking. These children also may have impaired intelligence and a head that is small in relation to their body size. Up to 20% of untreated infected children progressively lose social and language skills and muscle control. They may become partially paralyzed or unsteady on their feet, or their muscles may become somewhat rigid.

Anemia (a low red blood cell count—see Overview of Anemia) is common among HIV-infected children and causes them to become weak and tire easily. About 20% of untreated children develop heart problems, such as rapid or irregular heartbeat, or heart failure.

Untreated children also commonly develop inflammation of the liver (hepatitis—see Overview of Hepatitis) or inflammation of the kidneys (nephritis). Cancers are uncommon in children with AIDS, but non-Hodgkin lymphoma and lymphomas of the brain may occur somewhat more often than in uninfected children. Kaposi sarcoma (see Kaposi Sarcoma), an AIDS-related cancer that affects the skin and internal organs, is common among HIV-infected adults but is very rare in HIV-infected children.

With ART, children with HIV infection do not necessarily develop any symptoms of HIV infection. ART has significantly changed the way HIV infection manifests in children. Although bacterial pneumonia and other bacterial infections (such as bacteremia and recurring otitis media) occur slightly more often in HIV-infected children, opportunistic infections and growth failure are much less frequent than in the era before ART.

Although ART clearly lessens the effects of brain and spinal cord disorders, there seems to be an increased rate of behavioral, developmental, and cognitive problems in treated HIV-infected children. It is unclear whether these problems are caused by HIV infection itself, the drugs used to treat HIV, or other biologic, psychologic, and social factors that are common among HIV-infected children.

Because ART has allowed children and adults to survive for many years, more people are developing long-term complications of HIV infection. These complications include obesity, heart disease, diabetes, and kidney disease. These complications appear to be related both to HIV infection itself and to the effects of certain ART drugs.

The symptoms of HIV infection acquired during adolescence are similar to those in adults (see Human Immunodeficiency Virus (HIV) Infection : Symptoms).

Current preventive therapy for infected pregnant women is highly effective at minimizing transmission. HIV-infected pregnant women should begin ART by mouth. Ideally, ART should begin soon after HIV infection is diagnosed but at least during the 2nd and 3rd trimesters (last 6 months) of pregnancy. HIV-infected pregnant women who are already on ART should continue the therapy. The antiretroviral drug zidovudine (ZDV) is also given by vein (intravenously) during labor and delivery to many women. ZDV is then given to the newborn twice a day by mouth for 6 weeks. This treatment reduces the rate of transmission from 25 to 33% to about 1 to 2%. Also, cesarean delivery (c-section—see Cesarean Delivery) done before labor begins reduces the newborn's risk of acquiring HIV infection. Doctors may recommend cesarean delivery for women whose infection was not well controlled by ART.

In countries where good infant formulas and clean water are readily available, HIV-infected mothers should bottle-feed formula to their infants and should be advised never to breastfeed their infants or donate their breast milk to milk banks. In countries where the risks of undernutrition or infectious diarrhea resulting from using unclean water to feed infants or prepare formula are high, the benefits of breastfeeding outweigh the risk of HIV transmission. In these developing countries, HIV-infected mothers should continue to breastfeed for the first 6 months of the infant's life and then rapidly wean the infant to food.

Because a child's HIV status may not be known, all schools and day care centers should adopt special procedures for handling accidents, such as nosebleeds, and for cleaning and disinfecting surfaces contaminated with blood. During cleanup, personnel are advised to avoid having their skin come in contact with blood. Latex gloves should be routinely available, and hands should be washed after the gloves are removed. Contaminated surfaces should be cleaned and disinfected with a freshly prepared bleach solution containing 1 part of household bleach to 10 to 100 parts of water. These practices (called universal precautions) are followed not only for children with HIV infection, but for all children and in all situations involving blood.

Prevention for adolescents is the same as for adults (see Human Immunodeficiency Virus (HIV) Infection : Prevention). All adolescents should have access to HIV testing and should be taught how HIV is transmitted and how it can be avoided, including abstaining from high-risk behaviors and sex or using safe-sex practices.

To prevent Pneumocystis pneumonia, doctors give trimethoprim/sulfamethoxazole to certain children with proven HIV infection and a significantly impaired immune system and to all infants who were born to HIV-infected women beginning at 4 to 6 weeks of age (continued until testing shows the infants are not infected). Children who cannot tolerate trimethoprim/sulfamethoxazole can be given dapsone, atovaquone, or pentamidine.

Children with a significantly impaired immune system also are given azithromycin or clarithromycin to prevent Mycobacterium avium complex infection. Rifabutin is an alternative drug.

Children are treated with most of the same antiretroviral drugs as adults (see Antiretroviral drugs), typically an ART combination consisting of both of the following:

However, not all of the drugs used for adults are available to small children, in part because some are not available in liquid form. In general, children develop the same types of side effects as adults but usually at a much lower rate. However, the side effects of drugs may also limit the treatment. A doctor monitors the effectiveness of treatment by regularly measuring the amount of virus present in the blood and the child's CD4+ cell count (see Human Immunodeficiency Virus (HIV) Infection in Children : Diagnosis). Increased numbers of virus in the blood may be a sign that the virus is developing resistance to the drugs or that the child is not taking the drugs. In either case, the doctor may need to change the drugs. To monitor a child's progress, the doctor examines and does blood and other laboratory tests on the child at 3- to 4-month intervals.

Adherence to prescribed ART dosing schedules is extremely important. If children take ART drugs less often than they are supposed to, the HIV in their system can rapidly become permanently resistant to one or more of the drugs. Yet, it may be difficult for parents and children to follow and adhere to complicated drug regimens, which can limit the effectiveness of therapy. To simplify regimens and improve adherence, tablets containing three or more drugs may be given. These tablets may need to be taken only once or twice a day. The liquid forms of drugs are now better-tasting, which may improve adherence.

Adherence to ART may be more difficult for adolescents than for younger children. Adolescents also have difficulty adhering to treatment regimens for other chronic diseases such as diabetes and asthma. Adolescents want to be like their peers and can feel set apart by their illness. Skipping or stopping treatment may be a way for them to deny having an illness. Additional issues that may complicate treatment and reduce adherence in adolescents include

In addition, adolescents may not be able to understand why drugs are necessary when they do not feel ill and they may worry greatly about side effects. Despite frequent contact with a pediatric health care team, adolescents who have been infected since birth may fear or deny their HIV infection or distrust information provided by the health care team. Instead of directly confronting adolescents who have poor support systems about the need to take their drugs, care teams sometimes help the adolescent focus on practical matters such as how to avoid opportunistic infections and how to obtain information about reproductive health services, housing, and succeeding in school.

Nearly all HIV-infected children should receive the routine childhood vaccinations (see Childhood Vaccination Schedule), including

Some vaccines containing live bacteria, such as bacille Calmette-Guérin (which is used to prevent tuberculosis in some countries outside the United States), or live viruses, such as the oral polio virus, varicella, and measles-mumps-rubella, can cause a severe or fatal illness in children with HIV whose immune system is very impaired. However, the live measles-mumps-rubella vaccine and live varicella vaccine are recommended for children with HIV infection whose immune system is not severely impaired.

The live rotavirus vaccine may be given according to the routine schedule to infants exposed to or infected with HIV.

Yearly inactivated (not live) influenza immunization is also recommended for all HIV-infected children over 6 months of age, and inactivated or live immunization is recommended for household members.

However, the effectiveness of any vaccination is less in children with HIV infection. HIV-infected children with very low CD4+ cell counts are considered susceptible to vaccine-preventable diseases when they are exposed to one (such as measles, tetanus, or varicella) regardless of whether they have received the vaccine for that disease and may be given immune globulin by vein (intravenously). Intravenous immune globulin or immediate vaccination with measles-mumps-rubella vaccine also should be considered for any nonimmunized household member who is exposed to measles.

For children who need foster care, child care, or schooling, a doctor can help assess the child's risk of exposure to infectious diseases. In general, transmission of infections, such as chickenpox, to the HIV-infected child (or to any child with an impaired immune system) is more of a danger than is transmission of HIV from that child to others. A young child with HIV infection who has open skin sores or who engages in potentially dangerous behavior, such as biting, should not attend child care.

HIV-infected children should participate in as many routine childhood activities as their physical condition allows. Interaction with other children enhances social development and self-esteem. Because of the stigma associated with the illness, the routine use of universal precautions in schools and day care centers, and the fact that transmission of the infection to other children is extremely unlikely, there is no need for anyone other than the parents, the doctor, and perhaps the school nurse to be aware of the child's HIV status.

As a child's condition worsens, treatment is best given in the least restrictive environment possible. If home health care and social services are available, the child can spend more time at home rather than in a hospital.