Community and Public health for Medical Laboratory Science.

• HIV is a retrovirus, a virus that uses RNA as its genetic material instead of the more usual DNA.
• • The course of infection with HIV takes place over a number of years. After being exposed to HIV, a person may or may not notice mild, flu-like symptoms for a few weeks, during which time the virus is present in the blood and body fluids and may be easily transmitted to others by sex or other risky behaviors. The body’s immune system responds as it would to any viral infection, producing specific antibodies that eliminate most of the circulating viruses. 
• The infection then enters a latent period, with the viruses mostly hidden in the DNA of the T4 cells, although a constant battle is taking place between the virus and the immune system. Billions of viruses are made, and millions of T4 cells are destroyed daily.
• The immune system begins to lose the struggle, and so many of the T4 cells begin to die that they cannot be replaced rapidly enough. When the number of T4 cells drops below 200 per cubic millimeter of blood, about 20 percent of the normal level, symptoms are likely to begin appearing, and the person is vulnerable to opportunistic infections and certain tumors
• The major pathways of HIV transmission vary in different populations. Homosexual relations between men are still the leading route of exposure for men in the United States. Injection drug use accounts for 10 percent of new HIV infections in Americans.
• • Transmission by heterosexual relations, especially male to female, is becoming increasingly common in this country; it is the leading route of infection for females. In the developing countries of Asia and Africa, where HIV infection is spreading rapidly, heterosexual relations are the most common means of transmission.
• Several studies have found that circumcision protects men against contracting HIV from infected women; circumcision does not appear to protect women against contracting HIV from infected men. Studies of the effect of circumcision on male-to-male transmission have yielded mixed results.
• According to the World Health Organization (WHO), 40 percent of injections worldwide are given with unsterile needles. Transfusion with HIV-contaminated blood is no longer a significant source of HIV infection in the United States, but it still occurs in countries too poor to screen donated blood.
• A special case of HIV transmission occurs from mother to infant, in utero or during delivery, in 25 to 33 percent of births unless antiretroviral drugs are given. The virus can also be transmitted to breast-fed babies in their mother’s milk.
• All infants of HIV-positive women will test positive during the first few months after birth. This is The Biomedical Basis of AIDS 137 because fetuses in the womb receive a selection of their mothers’ antibodies, providing natural protection against disease (though not HIV) during their first months of life.
• • Drug therapies are now capable of preventing transmission of the virus from mother to infant in 99 percent of cases. Similar drug treatment of mothers and/or infants can prevent transmission in breast milk.
• Progress in treating HIV/AIDS over the past two decades has been dramatic. Early therapy focused on treating opportunistic infections, which were often the immediate cause of death in AIDS patients.
• The first antiretroviral therapy, zidovudine (AZT), was approved by the Food and Drug Administration (FDA) in 1987. The drug interfered with the replication of HIV by inhibiting the enzyme that copies the viral RNA into the cell’s DNA. However, the virus’s tendency to mutate rapidly leads to the development of resistance to the drug, meaning that its effectiveness can wear off.
• As scientists gained a better understanding of the virus, they developed drugs that target different stages of viral replication. Protease inhibitors, which interfere with the ability of newly formed viruses to mature and become infectious, were introduced in 1995. At the same time, scientists recognized that treating patients with a combination of drugs that attack the virus in different ways reduces the opportunity for HIV to mutate and develop resistance.
• The introduction of these drug combinations called highly active antiretroviral therapy (HAART), led to dramatic improvements in the survival of HIV-infected patients. As a result, the number of AIDS deaths fell by more than half between 1996 and 1998 and has continued to decline since then.
• Virus can survive extreme conditions such as treatment with alcohol and drying in a vacuum and become active again when they are injected into a living cell. They reproduce themselves by taking control of the cell’s machinery, often killing the cell in the process. The human diseases caused by this, include smallpox, yellow fever, polio, hepatitis, influenza, measles, rabies, and AIDS, as well as the common cold.
• Pertussis - Whooping Cough Vaccine
• About 40 percent of patients treated with protease inhibitors develop lipodystrophy, characterized by abnormal distributions of fat in the body, sometimes accompanied by other metabolic abnormalities. Moreover, the virus can develop resistance to these drugs if used improperly. A survey of blood samples taken between 1999 and 2003 found that 15 percent were resistant to at least one drug.
• New drugs continue to be developed, including a class called “fusion inhibitors,” introduced in 2003, which interfere with HIV’s ability to enter a host cell, and a class called integrase inhibitors, introduced in 2002, which prevents the virus from integrating into the genetic material of human cells.
• Thus for many patients, HIV infection has become a chronic disease, necessitating life-long therapy but enabling them to live a relatively normal life. The drugs are expensive however, costing an average of $23,000 per year per patient, and many insurance plans cover only a limited portion of the cost.
• Early hopes for the rapid availability of a vaccine against AIDS have faded, however. In fact, after several promising vaccine candidates failed in clinical trials, the National Institutes of Health (NIH) held a meeting of vaccine researchers in March 2008, to reassess whether a vaccine would ever be possible and what new approaches could be tried.
• At present, the most effective way to fight AIDS is to prevent transmission (step 3 in the chain of transmission). This requires education and efforts at motivating people to change their high-risk behavior, an exceedingly difficult task.
• HIV seems to have appeared from nowhere and to have spread over the entire world within a decade. Where did the virus come from? Genetic studies of HIV show that it is related to viruses that commonly infect African monkeys and apes, and it seems likely that a mutation allowed one of these viruses to infect humans.
• Symptoms of Acute HIV: Fever, Chills, Headaches, Night Sweats, Sore Throat, Muscle aches and pains, Joint pain, Fatigue, Swollen lymph nodes, mainly on the neck, and Mouth ulcers.
• The reasons for the recent emergence of HIV disease as a significant problem include the disruption of traditional lifestyles by the movement of rural Africans to urban areas, trends magnified by population growth, waves of civil war, and revolution.
• The apparent worldwide explosion of AIDS then occurred because of changing patterns of sexual behavior and the use of addictive drugs in developed and developing countries, together with the ease of international air travel.
• Ebola - In 1976, before the AIDS epidemic was recognized but while, as scientists now believe, the virus was spreading silently into African cities, another viral illness broke out with much more dramatic effect in Zaire and Sudan. Symptoms caused by the previously unidentified virus include fever, vomiting and diarrhea, and severe bleeding from various bodily orifices.
• Ebola - Several hundred people became ill from the disease, and up to 90 percent of its victims died. The disease spread rapidly from person to person, affecting especially family members and hospital workers who had cared for patients.
• The Ebola virus infects monkeys and apes as well as humans, and on a number of occasions infected monkeys have been imported into the United States. In 1989, a large number of monkeys imported from the Philippines died of the viral infection at a primate quarantine facility in Reston, Virginia. In that episode, which served as the basis for Richard Preston’s book, The Hot Zone, several laboratory workers were exposed to the virus, which fortunately turned out to be a strain that did not cause illness in humans.
• In 2014, a major Ebola epidemic spread through the populations of several countries in West Africa. Hardest hit were Liberia, Guinea, and Sierra Leone, poor countries that have been plagued by political unrest and inadequate medical care systems.
• More than 28,600 cases, with about 11,300 deaths, have been reported in the West African epidemic, and those numbers are thought to be undercounts.
• The virus came to the United States. The first patient was a Liberian man who became ill while visiting relatives in Dallas, Texas in September 2014. Thomas Eric Duncan was taken to a hospital, examined, and sent home with antibiotics. Although hospital staff were told he had been in Guinea, the information did not trigger alarm, and Ebola was not suspected. Three days later, Duncan’s condition worsened and he was taken back to the hospital, where he died on October 8.
• Two nurses who cared for Thomas Eric Duncan contracted the disease within days of his death. They were treated at two of four hospitals in the United States that have special units for treating dangerous infectious diseases: Emory University Hospital and the National Institutes of Health Clinical Center. Both women recovered.
• Another American patient of Ebola, Dr. Craig Spencer, arrived in New York in late October after treating patients in Guinea with Doctors Without Borders. He had been monitoring himself and was hospitalized at Bellevue Medical Center when he developed a fever. Dr. Spencer also recovered.
• The better outcomes achieved by American patients, compared with the high death rate among West Africans—which in some West African countries was more than 70 percent—is due in part to excellent supportive care provided to them in U.S. hospitals. One measure some of them received was transfusion with serum from survivors, which contains antibodies to the virus. Some patients were treated with ZMapp, an experimental drug.
• Dr. Ian Crozier, who contracted the disease when working with WHO in Sierra Leone and was evacuated to Emory University Hospital in September 2014, learned after his discharge that one eye was badly infected with virus and he was in danger of losing his sight. He was treated with an experimental drug and gradually recovered his vision. Many of the survivors have also reported other aftereffects of the disease, including extreme fatigue, joint and muscle pain, and hearing loss.
• Several drugs appear to show promise in treating Ebola, although none has yet proved itself effective in a clinical trial. ZMapp, a combination of three antibodies, proteins that can attach to the virus and neutralize them, has shown promise in monkey studies. It may have helped the nine patients in the United States that were treated with it, many of them healthcare workers returned from Africa.
• A drug called favipiravir, developed in Japan as a treatment for influenza, works by interfering with the virus’s ability to copy itself. It was given to a number of patients in Guinea and appeared to be helpful in patients whose viral load was low to moderate.
• An older anti-Ebola drug, TKM-Ebola, created to fight the strain prevalent in an earlier outbreak in Central Africa, has been adapted to the current West African strain and was found to be effective in treating monkeys infected with the virus. In March 2015, a clinical trial of TKM-Ebola was launched in Sierra Leone, where the disease was still spreading.
• Monkey Pox - The outbreak in the United States spread to 72 people in six Midwestern states. Fortunately, It is not highly contagious in humans, and it is a less severe disease than smallpox. No one died in the outbreak. However, the incident raised alarms about exotic pets.