|
Tuberculosis, Other Sexually Transmitted Diseases and Hepatitis B and C
Because of the interrelationships between tuberculosis (TB) sexually transmitted diseases (STD), HBV, HCV and HIV, a brief discussion of each of these is included in this course.
Tuberculosis and HIV
Globally, there are probably 2 billion people (1/3 of the world's population) infected with TB, and 8 million active cases of TB each year. Tuberculosis is one of the leading causes of death in the world.
Photo Courtesy of the Public Health Image Library.
Mycobacterium tuberculosis (TB) is the bacteria that cause tuberculosis. It is transmitted by airborne droplets from people with active pulmonary or laryngeal TB during coughing, sneezing, or talking. Although the TB bacteria can live anywhere in the body, infectious pulmonary or laryngeal TB poses the greatest threat to public health.
Latent infection, which is asymptomatic and not infectious, can last for a lifetime. A presumptive diagnosis of active TB is made when there are positive test results or acid-fast bacilli (AFB) in sputum or other bodily fluids. The diagnosis is confirmed by identification of M. tuberculosis on culture, which should be followed by drug sensitivity testing of the bacteria.
The TB bacteria are carried through the bloodstream and lymph system, pumped through the heart, and then disseminated through the body.
The largest amount of bacteria goes to the lungs. In most cases, this process, called primary infection, resolves by itself and something called "delayed-type hypersensitivity" is established. This is measured with the tuberculin skin test. The incubation period for this primary infection is two to 10 weeks. In most cases, a latent state of TB develops. 90% of people with latent TB never experience subsequent disease. Other than a positive tuberculin skin test, people with latent TB infection have no clinical, radiographic (x-ray), or laboratory evidence of TB and cannot transmit TB to others.
Among the other 10% of infected individuals, the TB infection undergoes "reactivation" at some time and they develop active TB. About 5% of newly infected persons do so within the first two years of primary infection and another 5% will do so at some point later in life.
The period from time of initial exposure to conversion of the tuberculin skin test is four to 12 weeks. During this period, the patient shows no symptoms. The progression to active disease and symptoms, such as cough, weight loss, and fever, usually occurs within the first two years after infection, but may occur at any time.
It is important to recognize the behavioral barriers to TB management, which include deficiencies in treatment regimens, poor client adherence to TB medications, and lack of public awareness. Primary healthcare providers need adequate training in screening, diagnosis, treatment, counseling, and contact tracing for TB through continuing education programs and expert consultation. Promoting patient adherence to the sometimes complicated medication schedule, also requires consideration of the patient's cultural and ethnic perceptions of his/her health condition. Providing strategies and services that address the multiple health problems associated with TB (such as alcohol and drug abuse, homelessness, and mental illness) also builds trust and promotes adherence to treatment plans.
Clinical trials have shown that daily preventive therapy for 12 months reduces the risk for TB disease by more than 90% in patients with latent TB infection who complete a full course of therapy. There is evidence that six months of preventive therapy with Isoniazid may also prevent disease in approximately 69% of patients who complete the regimen. Every effort should be made to ensure that patients adhere to this therapy for at least six months. Children should receive at least nine months of preventive therapy.
In order to prevent drug resistance and cure TB, the CDC recommends that TB be treated with a multidrug regimen, which may last six to 12 months.
Treatment of multidrug-resistant TB (MDR-TB) is much more difficult and must be individualized. The patient with MDR-TB requires treatment for two years or more.
TB/HIV Co-infection
HIV/TB co-infected persons are at considerably greater risk of developing TB disease than those who only have TB. Studies suggest that the risk of developing TB disease is 7% to 10% each year for persons who are infected with both M. tuberculosis and HIV, whereas it is 10% over a lifetime for a person infected only with M. tuberculosis.
In an HIV-infected person, TB disease can develop in either of two ways. A person who already has latent TB infection can become infected with HIV, and then TB disease can develop as the immune system is weakened. Or, a person who has HIV infection can become infected with M. tuberculosis and TB disease can then rapidly develop because their immune system is not functioning.
Pulmonary TB and extrapulmonary TB are among the conditions included in the 1993 AIDS surveillance case definition. Any HIV-infected person with a diagnosis of TB disease should be reported as having TB and AIDS.
Other Sexually Transmitted Diseases and HIV
The term sexually transmitted disease (STD) is not specific for any one disease, but refers to the more than 25 infectious organisms that are transmitted through sexual activity and the dozens of clinical syndromes that they cause. STDs affect both men and women and can also be transmitted from mothers to babies during pregnancy and childbirth. These may also be called sexually transmitted infections (STIs).
Fluorescent antibody-stained micrograph depicts a positive result testing for the presence of gonorrhea. Courtesy of Public Health Image Library.
 |
Different bacteria cause STDs such as chlamydia, gonorrhea and syphilis. Herpes, genital warts, hepatitis B and HIV have different viral causes. Scabies are caused by mites, and pubic lice cause "crabs." Trichomoniasis is caused by tiny organisms called protozoa; "yeast" infections are caused by fungi. STDs such as pelvic inflammatory disease can have more than one cause - a woman may have both gonorrhea and chlamydia causing this condition. A man may have more than one cause for epididymitis.
In 1999, the World Health Organization estimated that there were 340 million new cases of the four common curable STDs (gonorrhea, chlamydia, syphilis and trichomoniasis) worldwide among people age 15-49. Since the beginning of the AIDS epidemic, researchers have noted the strong association between HIV and other STDs.
Nationally, five of the top 10 most frequently reported communicable diseases are STDs. In the US in 1999, 659,441 new cases of chlamydia were reported to the CDC. Reported cases of gonorrhea rose to 360,076 in that year.
|
Primary and secondary cases of syphilis declined to 6,657 cases. The Kaiser Family Foundation's website (www.kff.org) lists estimates for incidence (new cases) and prevalence (total number of cases) of both bacterial and viral STDs in the US, noting that by age 24, at least one in three sexually active people are estimated to have contracted an STD.
Primary STD infections may cause pregnancy-related complications, congenital infections, infertility, ectopic pregnancy, chronic pelvic pain and cancers. STDs can also accelerate other infections like HIV.
HIV and STDs
STDs are transmitted in the same way that HIV is transmitted: by anal, vaginal and oral sex. In addition, skin-to-skin contact is important for the transmission of herpes, genital warts, syphilis, scabies and pubic lice.
In the past, there was a great emphasis on symptoms as indicators of STD infection. Research has changed this. We now know that 80% of those with chlamydia, 70% of those with herpes and a great percentage of those with other STDs have no symptoms, but can still spread the infections.
Along with prompt testing and treatment for those who do have symptoms, the emphasis in the U.S. is screening for infection based on behavioral risk. Patients cannot assume that their healthcare providers do STD testing. In other words, women who are getting a pap test or yearly exam should not just assume that they are also being tested for chlamydia or any other STD.
At some sites, new urine LCR tests for some STDs are available. Western Blot blood tests for herpes and hybrid capture tests for genital warts may also be available. In most places, however, cultures, wet preps and blood draws for syphilis remain the standard testing method. It is vital that women get pap tests, and that both men and women disclose a history of STD during medical workups.
STD treatment is based on lab work and clinical diagnosis. Treatments vary with each disease or syndrome. Because of developing resistance to medications for some STDs, check the latest CDC treatment guidelines.
Hepatitis B and HIV
Hepatitis is the inflammation of the liver that may be caused by many things, including viruses. Current viruses include Hepatitis A (not usually sexually transmitted or transmitted by blood), B, C, D and others.
Hepatitis B (HBV) is a virus that is transmitted by the blood and body fluids of an infected person.
A vaccine to prevent HBV is available. It is taken in a series of three injections over 6 months. More than 90% of people who take the 3 injections become immune to HBV.
Hepatitis B virus under electron microscope. Courtesy of Public Health Image Library.
HBV vaccine is relatively inexpensive for infants and children. The adult doses are more expensive (costing about $150 per person.) This cost is the likely reason that most adults are not vaccinated against HBV.
Each year in the U.S. an estimated 200,000-300,000 people become infected with HBV. Of these, about 10% of adults will become chronically infectious carriers of the virus. There are 1,250,000 carriers of HBV in the U.S. Each year, over 11,000 people will be hospitalized and about 4,000-5,000 people will die in the U.S. from chronic liver disease or liver cancer caused by HBV.
HBV is transmitted the same way as HIV, through sexual intercourse and sharing needles. HBV is much more concentrated in blood, and it is more infectious than HIV.
The average incubation period for HBV is 120 days. People are infectious when they are "Hepatitis B surface antigen positive" (HbsAg) either because they are newly infected, or because they are chronic carriers.
Most people recover from their HBV infection and do not become carriers. Carriers (about 10% of adults who become infected) have the virus in their body for months, years, or for life. They can infect others with HBV through their blood or other body fluid contact.
HBV causes damage to the liver and other body systems, which can range in severity from mild, to severe, to fatal.
Others who are infected with HBV experience more severe symptoms, and may be incapacitated for weeks or months.
A vaccine for HBV has been available since prior to 1990. This vaccine is suitable for people of all ages, even infants. People who may be at risk for infection should get vaccinated.
Infants born to mothers who are HBV carriers have a greater than 90% reduction in their chance of becoming infected with HBV, if they receive a shot of hepatitis B immune globulin and hepatitis B vaccine shortly after birth plus two additional vaccine doses by age six months.
It is vital that the women and their medical providers are aware that the woman is a HBV carrier.
People with HBV should not donate blood, semen or body organs.
There is no cure for HBV. There are two approved drug treatments for HBV, but these treatments do not cure, the virus. The vaccine is not used to treat HBV infection once a person is infected.
Hepatitis C and HIV
Hepatitis C is a liver disease caused by the hepatitis C virus (HCV), which is found in the blood of persons who have this disease. Hepatitis C is the leading cause of chronic liver disease in the United States. Hepatitis C was discovered in the late 1980s, although it was likely spread for at least 40-50 years prior to that.
Globally, 200 million people are infected with HCV. As of 1999, almost 4 million Americans, or 1.8% of the U.S. population, have antibodies to HCV. This means that they have a current or previous infection with the virus. About 3 million are chronically infected, and the majority of them have some liver damage.
The CDC estimates that as many as 1 million Americans were infected with HCV from blood transfusions, and that 3.75 million Americans do not know they are HCV-positive. Of these, 2.75 million people are chronically infected, and are infectious for HCV. In the U.S., 8,000-10,000 deaths per year are attributed to HCV-associated liver disease. The number of deaths from HCV is expected to triple in the next 10-20 years.
HCV is transmitted primarily by blood and blood products. Blood transfusions and the use of shared or unsterilized needles and syringes have been the main causes of the spread of HCV in the US. The primary way that HCV is transmitted now is through injection drug use. Since 1992, all blood for donation in the U.S. is tested for HCV.
Sexual transmission of HCV accounts for 10 - 20% of new infections, but is unusual. If a pregnant woman is infected with HCV, she may pass the virus to her baby. However, this occurs in only about 5% of those pregnancies.
Household transmission is possible if people share personal care items such as razors, nail clippers, toothbrushes, etc.
People with HCV should not donate blood, semen or body organs.
Currently there are two approved antiretroviral treatments for HCV. The cost of the treatments can be high, and the side effects can be significant (fatigue, flu-like symptoms, nausea, depression and anemia). People infected with HCV should abstain from alcohol use, as this can further damage the liver.
Many people who are infected with HCV are unaware of their status.
Testing for HCV is available through physicians and some health departments.
In 1999, the Food & Drug Administration approved the first home test for HCV. The test kit, called "Hepatitis C Check" is available from the Home Access Health Company. The test is accurate if it has been at least six months since the possible exposure to HCV.
HIV/HCV Coinfection
Many people who become infected with HIV from injection drug use are already infected with HCV. Some estimate that 40% of HIV-infected people in the U.S. are also infected with HCV. People who are co-infected with both viruses and have immune system impairment, may progress faster to serious, chronic or fatal liver damage.
Most new HCV infections in the U.S. are among injecting drug users. The majority of hemophiliacs who received blood products contaminated with HIV also are infected with HCV. Treating HIV in someone with HCV may be complicated, because many of the medicines that are used to treat HIV may damage the liver.
Continue on to
|
Infection
