HIV stands for human immunodeficiency virus. This is a virus in the group of viruses called retroviruses. HIV destroys cells in the body called CD4 T-cells. CD4 T-cells are a type of lymphocyte (a white blood cell). These are important cells that protect the body against various bacteria, viruses and other 'germs'. HIV actually multiplies within CD4 cells. HIV cannot be destroyed by white blood cells as it keeps on changing its outer coat so protecting it.
AIDS stands for acquired immunodeficiency syndrome. This is a term which covers the range of infections and illnesses which can result from a 'weakened' immune system caused by HIV.
• Sexual transmission. This is the most common way the virus is passed on. You can become infected if you have sex with an infected person (vaginal, anal or oral sex). Semen, vaginal secretions and blood from an infected person contains HIV. The virus can enter the body through the lining of the vagina, vulva, penis, rectum or mouth during sex.
• Needle sharing. HIV (and other viruses such as hepatitis B and C) can be transmitted by drug users who share needles, syringes and other injecting equipment which is contaminated with infected blood.
• Infected blood. In the past quite a number of cases occurred from infected blood transfusions and other blood products. This is now rare in the UK as since 1985 all blood products are checked for HIV before being used. It is still a significant problem in developing countries.
• Accidental needlestick injuries. The risk is extremely low; health care workers who have been injured accidentally by contaminated needles only have a risk of 3 in 1000.
• From mother to child. Pregnant women with HIV can pass the infection on to their babies during pregnancy or childbirth. Studies suggest that about 1 in 7 babies born to HIV-infected mothers are likely to be infected, although this is higher in Africa. However, treatment with anti-HIV drugs during pregnancy greatly reduces the risk of passing on the virus. Having a caesarean section to deliver the baby reduces the risk even further. HIV can occasionally be passed to babies through breast milk during breastfeeding. If formula milk is available, mothers with HIV are encouraged not to breastfeed.
Blood pressure is the pressure of blood in your arteries (blood vessels). Blood pressure is measured in millimetres of mercury (mmHg). Your blood pressure is recorded as two figures. For example, 150/95 mmHg. This is said as '150 over 95'.
• The top (first) number is the systolic pressure. This is the pressure in the arteries when the heart contracts.
• The bottom (second) number is the diastolic pressure. This is the pressure in the arteries when the heart rests between each heartbeat.
High blood pressure is a blood pressure that is 140/90 mmHg or above each time it is taken. That is, it is 'sustained' at 140/90 mmHg or above. High blood pressure can be:
• Just a high systolic pressure, for example, 170/70 mmHg.
• Just a high diastolic pressure, for example, 120/104 mmHg.
• Or both, for example, 170/110 mmHg.
However, it is not quite as simple as this. Depending on various factors, the level at which blood pressure is considered high enough to be treated with medication can vary from person to person.
Blood pressure of 160/100 mmHg or above
This is definitely high. All people with a blood pressure that stays at this level are usually offered medication to lower it (described later).
Blood pressure of 140/90 mmHg or above but below 160/100 mmHg
This is sometimes called 'mild' high blood pressure. Ideally, it should be lower than this but for many people the risk from mild high blood pressure is small, and drug treatment is not indicated. However, certain groups of people with blood pressure in this range are advised medication to lower it. These are people with:
• a high risk of developing cardiovascular diseases (see below), or
• an existing cardiovascular disease (see below), or
• diabetes, or
• damage to the heart or kidney (organ damage) due to high blood pressure.
Blood pressure between 130/80 and 140/90 mmHg
For most people this level is fine. However, current UK guidelines suggest that this level is too high for certain groups of people. Treatment to lower your blood pressure if it is 130/80 mmHg or higher may be considered if you:
• Have developed a complication of diabetes, especially kidney problems.
• Have had a serious cardiovascular event such as a heart attack, transient ischaemic attack (TIA) or stroke.
• Have certain chronic (ongoing) kidney diseases.
Cardiovascular diseases are diseases of the heart (cardiac muscle) or blood vessels (vasculature). However, in practice, when doctors use the term 'cardiovascular disease' they usually mean diseases of the heart or blood vessels that are caused by atheroma. Patches of atheroma are like small fatty lumps that develop within the inside lining of arteries (blood vessels). Atheroma is also known as 'atherosclerosis' and 'hardening of the arteries'.
Cardiovascular diseases that can be caused by atheroma include: angina, heart attack, stroke, transient ischaemic attack (TIA), and peripheral vascular disease. In the UK, cardiovascular diseases are a major cause of poor health and the biggest cause of death.