Viral Diseases Hivaids

The acquired immunodeficiency syndrome (AIDS) is caused by a retrovirus known as the human immunodeficiency virus (HIV), which attacks and impairs the body's natural defence system against disease and infection. HIV is a slow-acting virus that may take years to produce illness in a person. During this period, an HIV-infected person's defence system is impaired, and other viruses, bacteria and parasites take advantage of this "opportunity" to further weaken the body and cause various illnesses, such as pneumonia, tuberculosis and mycosis. When a person starts having such opportunistic infections, he or she has AIDS. The amount of time it takes for HIV infection to become full-blown AIDS depends on the person's general health and nutritional status before and during the time of HIV infection. The average time for an adult is approximately 10 years without antiretroviral therapy (ART). Women are more likely to be infected with HIV than men. Children are also at risk (4).

The number of people living with HIV globally has reached its highest level with an estimated 40.3 million people, rising from an estimated 37.5 million in 2003. More than three million people died of AIDS-related illnesses in 2005; more than 500 000 of them were children. Sub-Saharan Africa continues to be the most affected region globally, with 64% of new infections occurring there. HIV treatment has improved markedly, however, and hundreds of thousands of people are now living longer in better health because they are receiving ART: an estimated 250-350 000 deaths were averted in 2005 because of expanded access to HIV treatment (5).

Neurological complications occur in 39-70% of patients with AIDS and significantly impact on functional capacity, quality of life and survival. Neuropathological examination identifies abnormal neurological conditions in more than 90% of autopsies but is not always demonstrated clinically (6). The main etiological considerations include primary HIV-related syndromes, opportunistic conditions, inflammatory conditions, and medications (7) (see Table 3.5.1).

Table 3.5.1 Neurological diseases in the HIV-infected individual

Type of condition

Examples

Primary HIV-related syndromes

HIV-associated cognitive-motor complex HIV-associated myelopathy HIV-associated polyneuropathy HIV-associated myopathy

Opportunistic conditions

Toxoplasma encephalitis Cryptococcal meningitis Cytomegalovirus encephalitis/polyradiculitis Progressive multifocal leukoencephalopathy Primary central nervous system lymphoma

Inflammatory conditions

Acquired demyelinating neuropathies Aseptic meningitis

Treatment-associated conditions

Zidovudine-induced myopathy Nucleoside analog-induced neuropathy

Multiple investigations in recent years suggest that the effects of neurological complications and opportunistic infections related to HIV have a clear trend to diminish since the introduction of new and more powerful antiretroviral agents. Nevertheless, prolonging the life of patients infected by the virus, attributable to therapeutic success, paradoxically favours the emergence of some neurological affections as treatment-associated neuropathy/myopathy; these affections can be more important than the benefits of therapy to achieve viral suppression.

Accurately diagnosing neurological disease in the HIV-infected individual is crucial for several reasons. First, many complications are treatable and their treatment can lead to either increased survival or improved quality of life. Second, identifying currently untreatable conditions provides the patient with the opportunity to participate in a growing number of therapeutic trials. Further, an accurate and focused diagnostic assessment and treatment plan will limit therapeutic misadventures and lead to cost-effective care delivery.

The worldwide use of highly active antiretroviral therapy (HAART) has played an important role in changing the incidence of neurological complications in AIDS patients. Recent studies have shown that HAART has produced both quantitative and qualitative changes in the pattern of HIV neuropathology: an overall decrease in the incidence of some cerebral opportunistic infections such as toxoplasmosis and cytomegalovirus encephalitis, for which successful treatment is available, whereas other uncommon types and new variants of brain infections, such as varicella-zoster encephalitis, herpes simplex virus encephalitis or HIV encephalitis, are being reported more frequently as ART promotes some immune recovery and increases survival (8). In developing countries, some endemic infections such as tuberculosis and Chagas disease have re-emerged in direct association with the spreading of HIV, and are now being considered as markers of AIDS.

Unfortunately, some patients may develop paradoxical clinical outcomes after starting treatment with HAART, known as neurological immune restoration inflammatory syndrome (NIRIS). Some treatment-related neurological disorders, like zidovudine-induced myopathy, nucleoside analog-induced neuropathy and efavirenz-induced neuropsychiatric disorders, can be more important than the benefits of the therapy of viral suppression (9).

Some therapies can prevent, treat or even cure many of the opportunistic infections and relieve the symptoms associated with them, but there is no cure for HIV/AIDS. The core benefit of HAART lies in its ability to reduce the rate of opportunistic infections by enhancing immune function, slowing viral replication in the body and thereby improving patients' quality of life and diminishing mortality. The cost of antiretroviral drugs is declining but, unfortunately, the treatments are still not affordable or accessible for most people.

Nevertheless, these important advances over the last decade have transformed HIV infection from a short-term, inevitably fatal disease to a chronic condition amenable to medical management, similar to diabetes or congestive heart failure.

It is important to integrate HIV prevention and care, and the challenges are immense: worldwide, fewer than one in five people at risk of becoming infected with HIV has access to basic prevention services. Of people living with HIV, only one in ten has been tested and is aware of the infection. For prevention interventions to achieve the results necessary to get ahead of the epidemic, projects with short-term horizons must translate into long-term programmatic strategies. In settings in which HIV is largely sexually transmitted, information and education campaigns can save lives. For example, intensive prevention programmes in the Mbeya region of the United Republic of Tanzania led to an increase in the use of condoms and the treatment of sexually transmitted infections between 1994 and 2000; those changes were accompanied by a decline in HIV prevalence among 15-24-year-old women from 21% to 15% in the same period {10). In settings in which HIV transmission is linked more closely to injecting drug use, harm-reduction strategies {for example, the provision of clean injecting equipment as well as adequate therapy for drug dependence) have proved to be effective. Other measures include voluntary counselling and testing, and improving women's health — including access to family planning and safe childbirth — in order to prevent HIV transmission from mother to infant. There is no cure for HIV/AIDS.

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