Avert, a charitable organization based in the UK, has the sole aim of containing the spread of HIV/AIDS by educating people about the disease and its causes. According to Avert, HIV is contracted via unprotected anal sex predominantly. The anal canal is a very sensitive area and is more prone to injuries and ruptures during intercourse and, therefore, it is probably even more delicate than the vagina. The injuries in the canal are the entry points of the virus during unprotected anal sex. 

According to AIDS.org, there is a probability of 62 to 66 percent of contracting HIV virus through unprotected vaginal intercourse. This happens when precautions, such as condom usage, are not taken and the sexual body fluids of the infected person enter the other through cuts and lesions on the sex organs. 

According to AIDS.org, there is an estimated 30 percent probability of contracting HIV virus by using intravenous drugs when sharing a needle/syringe with an infected person. The Centers for Disease Control and Prevention (CDC), based in Atlanta, provides the reason: the HIV virus is passed via the infected blood that often remains within the used needle which can ultimately infect the person who shares the syringe. This kind of contraction of HIV is common when people use illegal drugs, but it can also happen when people are unknowingly administered a used syringe in the hospital when given an intravenous prescription drug. Hence, make sure you are using a sealed and fresh syringe.

The probability of contracting HIV via oral sex is below 5 percent as per the studies conducted by the University of California, San Francisco. In the case of oral sex, the HIV virus enters the human body via cuts and lesions inside an unaffected person’s mouth. It can also occur when the blood from the cut or sore inside the mouth of an HIV positive person’s mouth enters the system of the uninfected partner. As per AIDS.org, oral intercourse is another cause of contracting HIV, but the risk of getting it rises when a person has sores and cuts inside the mouth.

As per AIDS.org, there are 20 to 30 percent chances of babies contracting HIV from their mothers during pregnancy or delivery. However, the chances of contracting HIV during delivery remain the highest. HIV virus can be transmitted to the unborn child during pregnancy via the placenta, as per the reports by CDC. However, there are certain medications that can be prescribed for HIV positive expectant mothers in order to reduce the probability of their newborns contracting the virus during delivery. Therefore, doctors prefer Cesarean deliveries in order to prevent the HIV virus from entering the baby. 

According to Avert, there is a 14 percent chance of HIV positive mothers passing on the virus to their infants via breastfeeding. However, if the mother is on antiviral drugs, then this probability can be reduced to near about 4 percent. As per the CDC, the HIV virus is found in the break milk of HIV positive mothers, therefore, it is prescribed for them to feed their infants formula milk via bottles in order to prevent the virus from entering the latter’s bodies.

According to reports from the Mayo Clinic, it is stated that there is a higher chance of contracting the HIV virus when an uninfected person comes into contact with HIV positive blood. However, as per Avert, the probability of this occurring is below 5 percent as there have been a lot of advancements in testing and screening the disease.

The probability of contracting HIV via body piercing and tattoos when done with used equipment are as low as being below 4 percent. However, it is pertinent for the person getting the tattoo or body piercing to check that the equipment is disposable and not used again in order to make it a safe experience.

According to the Centers for Disease Control and Prevention, there is a probability of less than 3 percent of contracting HIV through the accidental pricking of a needle. However, it must be understood that this is a rare probability as most health care centers and hospitals follow strict guidelines in safe disposal of used needles. 

According to the reports by the Centers for Disease Control and Prevention, there is a very small chance of contracted HIV via sports wherein two wounded athletes (with one being HIV positive) inadvertently transfers the virus to the uninfected athlete via a flesh wound.