Infectious diseasesepidemiology and surveillance

Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures | International measures | Additional sources of information

Victorian statutory requirement

Both HIV infection and AIDS are Group D notifications. A separate notification form is required for HIV and AIDS diagnoses. Written notification is required within five days of the initial diagnosis.

School exclusion is not required unless the child has a secondary infection.

Infectious agent

Human immunodeficiency virus (HIV) types 1 and 2 are a member of family retroviridae. A number of subtypes exist within HIV–1 and HIV–2.

Identification

Clinical features
AIDS is a severe, life-threatening disease that represents the late clinical stage of infection with the HIV. Several weeks after infection with HIV, a number of infected individuals will develop a self-limited glandular fever-like illness lasting for a week or two. Infected persons may then be free of clinical signs or symptoms for months or years.

Treatment with antiretroviral medication has resulted in fewer cases of AIDS. The burden of illness is now increasingly due to non-AIDS infections, toxicities related to antiretroviral therapy including changes in body shape and metabolic markers such as diabetes and high cholesterol, and neurological and psychiatric manifestations of HIV.

Untreated individuals are at risk of specific opportunistic infections and malignancies and a range of other AIDS indicative diseases. Major diseases that may be indicative of AIDS include:

• Pneumocystis carinii pneumonia
• oesophageal candidiasis
• Kaposi’s sarcoma
• chronic herpes simplex infection
• cryptococcosis
• cryptosporidiosis
• toxoplasmosis
• cytomegalovirus infection
• mycobacteriosis
• lymphoma
• HIV encephalopathy
• HIV wasting disease

Method of diagnosis
Careful history and physical examination looking for risk factors and clinical manifestations of immunodeficiency are necessary.

Diagnostic testing includes:

• detection of HIV antibody by the ELISA screening test and confirmation by Western blot analysis
• detection of the viral p24 antigen in serum
• PCR tests to detect pro-viral DNA sequences
• HIV culture, although this is only performed in certain special clinical situations.

Incubation period

The period from infection to the primary seroconversion illness is three to eight weeks. The period from infection to development of anti-HIV antibodies is three weeks to three months.

The interval from HIV infection to the diagnosis of AIDS ranges from about nine months to 20 years or longer, with a median of 12 years. There is a group of people with a more rapid onset of disease who develop AIDS within three to five years of infection. Treatment with antiretroviral drugs and disease-specific prophylaxis has resulted in an 80% reduction in AIDS-associated illnesses.

Public health significance & occurrence

Occurrence is worldwide. There were 40 million people living with HIV/AIDS by the end of 2001 and in 2000 three million people died from HIV-related illnesses. The vast majority of HIV infections occur in developing countries.

For the period 1983 to 2003 there was a cumulative total of 4680 HIV diagnoses in Victoria. This represents about 21% of Australia’s total. Males accounted for 94% of the diagnoses. Male to male sexual contact including homosexual and bisexual contact accounts for the majority of new diagnoses in men. In females, heterosexual contact and injecting drug use are the most common risk factors.

Reservoir

Humans.

Mode of transmission

HIV can be transmitted from an infected person by:

• Sexual exposure to infected semen, vaginal fluids and other infected body fluids during unprotected sexual intercourse with an infected person. This includes oral sex.
• Inoculation with infected blood, blood products and through transplantation of infected organs such as bone grafts or other tissues, or by artificial insemination with infected semen.
• Breastfeeding of an uninfected infant by an HIV-positive mother. Interventions that decrease the risk of vertical transmission from an infected woman to her child include antiretroviral therapy during pregnancy and caesarean section. Avoiding breastfeeding also decreases transmission. With these interventions the risk of mother to child transmission is less than 5%. If there is no intervention, the risk of mother to child HIV transmission has been estimated to be 20–45%.
• Sharps injuries including needle stick injuries or other exposure to blood and body fluids. The rate of seroconversion following a needle stick injury involving HIV infected blood is said to be less than 0.5%, but this is dependent on the type of needle stick injury (deep versus shallow) and the viral load of the infected person.

Period of communicability

All antibody positive persons carry the HIV virus.

Infectivity is presumed to be life long, although successful therapy with antiretroviral drugs can lower the viral load in blood and semen to undetectable levels.

Susceptibility & resistance

Everyone is susceptible to infection.

The presence of other sexually transmitted infections, especially those with skin or mucosal ulceration, may increase susceptibility.

Control measures

Preventive measures
Preventive measures for HIV centre on personal and institutional factors.

Personal factors include:

• public education on the use of condoms and safer sex practices
• public education should stress that having unprotected sex with unknown or multiple sexual partners and sharing needles (drug users) increases the risk of infection with HIV
• unprotected sexual intercourse with persons with known or suspected HIV infection should be avoided
• HIV-infected persons should be offered confidential counselling and access to screening and treatment for sexually transmissible infections and appropriate antiviral therapy for HIV
• care should be taken when handling, using and disposing of needles or other sharp items
• use of needle exchange programs by injecting drug users should be facilitated.

Institutional factors include:

• use of appropriate infection control measures by all health care and emergency workers
• use of appropriate infection control measures in all premises where skin penetration is carried out, for example electrolysis, tattooing or body piercing
• blood and blood products for transfusion and the donors of tissues and body fluids such as semen should be tested for the presence of markers of HIV
• sharps injuries, including needle stick injuries, and parenteral exposure to laboratory specimens containing HIV should be dealt with according to Infection control guidelines for the prevention of transmission of infectious diseases in the health care setting.
• non- occupational exposure to infected blood or body fluids should be assessed and managed according to the National guidelines for post-exposure prophylaxis after non-occupational exposure to HIV.

Control of case
Standard precautions (see Appendix 3) apply to all patients.

Additional transmission-based precautions apply for specific infections that occur in AIDS patients such as tuberculosis. Equipment contaminated with blood or body fluids should be cleaned and then disinfected or sterilised as appropriate.

Patients and their sexual partners should not donate blood, organs or other human tissue.

All HIV positive persons should be evaluated for the presence of tuberculosis.

Treatment
Anti-retroviral drug therapy is used to treat established HIV infection. As such treatment is specialised and constantly changing, only those doctors experienced in HIV management should prescribe antiretroviral therapy. For further information, see the current edition of the Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited). Other treatment includes specific treatment or prophylaxis for the opportunistic infectious diseases that result from HIV infection.

Control of contacts
If a person is diagnosed as having HIV infection, the diagnosing practitioner has a responsibility to ensure that sexual and needle-sharing contacts are followed up where possible.

Assistance with partner notification may be provided by Department of Human Services through its partner notification officers.

Pre and post-test counselling must be provided for all contacts seeking HIV testing.

Control of environment
The procedure for dealing with spills of blood and body fluids is in Appendix 5.

Outbreak measures

The epidemiology of HIV is closely monitored in Victoria and public health action is informed by enhanced epidemiological information notified to the Department.

Special settings
Health care workers
Registration boards should be consulted in relation to their policies regarding health care workers with blood-borne viruses. For example, the Medical Practitioners Board of Victoria (now Australian Health Practitioner Regulation Agency) has a policy on medical practitioners and medical students who carry a blood-borne virus, which is available at Australian Health Practitioner Regulation Agency website. Recommendations are also included in 'Recommendations are also included in the Australian Guidelines for the Prevention and Control of Infection in Healthcare' at the National Health and Medical Research Council (NHMRC).

Antenatal care
Antenatal care should include a comprehensive assessment of HIV risk factors. Women found to be at higher risk of HIV infection or exposure should be encouraged to undergo HIV antibody screening.

Other settings
All workplaces should have policies and procedures in place regarding action to be taken in the event of a blood spill or sharps injury. Further information can be found in Australian guidelines for the prevention and control of infection in healthcare, 2010.

International measures

WHO initiated a global prevention and control program in 1987. Since 1995, the global AIDS program has been coordinated by UNAIDS. Nearly all countries have developed an AIDS prevention and care program.

Additional sources of information

• Australian Government Department of Health and Family Services 1997, Contact tracing manual – A practical handbook for health care providers managing people with HIV, viral hepatitis, other STDs and HIV-related tuberculosis, Australian Government Department of Health and Family Services.
• Australasian Society for HIV Medicine Inc 2001, HIV/Viral hepatitis – A guide for primary care, http://www.ashm.org.au/
• Centers for Disease Control 2001, ‘Updated U.S. Public health service guidelines for the management of occupational exposures to HBV, HCV, and HIV and recommendations for postexposure prophylaxis’, MMWR, vol. 50, RR11, pp. 1–42, http://www.cdc.gov/mmwr
• Fleming, DT & Wasserheit, JN 1999, ‘From epidemiological synergy to public health policy and practice: the contribution of other sexually transmitted diseases to sexual transmission of HIV infection’, Sexually transmissible infections, vol. 73, pp. 3–17.
• Venereology Society of Victoria 2002, National management guidelines for sexually transmissible infections, Venereology Society of Victoria, http://www.mshc.org.au
• Australian Government Department of Health, The sixth national HIV strategy 2010-2013
  
• Working Group of the UK Chief Medical Officer’s Expert Advisory Group on AIDS 2000, Review of the evidence on risk of HIV transmission associated with oral sex – report of a working group of the UK Chief Medical Officer’s Expert Advisory Group on AIDS, Department of Health, London.