Needle Stick Injury (Healthcare)
Unprotected Sex (Receptive Anal)
Unprotected Sex (Insertive Anal)
Unprotected Sex (Receptive Vaginal)
Unprotected Sex (Insertive Vaginal)
Needle Sharing (IV Drug User)
Known Positive
Unknown
Known Negative
Understanding HIV Infection Risk
This calculator is designed to provide an estimated risk of HIV infection based on several key factors. It's crucial to understand that this is a simplified model and should not replace professional medical advice. For accurate assessment and management, consult a healthcare provider immediately after a potential exposure.
Factors Considered:
Type of Exposure: Different activities carry different baseline risks. For instance, needle-stick injuries in healthcare settings or specific types of sexual contact can have varying probabilities of transmission.
Viral Load of the Source: The concentration of HIV in the infected person's blood or bodily fluid. A higher viral load generally means a higher risk of transmission.
Source HIV Status: Whether the source person is known to be HIV-positive significantly impacts the calculation. If unknown, a conservative estimate may be used.
Time Since Exposure: Prompt initiation of Post-Exposure Prophylaxis (PEP) is critical. PEP is most effective when started within hours of exposure and is generally recommended up to 72 hours. This calculator uses time in hours to guide the urgency of seeking medical attention.
How the Calculation Works (Simplified Model):
The calculation is based on estimated baseline transmission probabilities for different exposure types, modified by the viral load and the source's HIV status. The time since exposure is critical for determining the urgency of seeking medical care for PEP.
Baseline Probabilities (Estimates): These are derived from various studies and guidelines. For example:
Needle Stick Injury (Healthcare): ~0.3%
Unprotected Receptive Anal Sex: ~1.38%
Unprotected Insertive Anal Sex: ~0.11%
Unprotected Receptive Vaginal Sex: ~0.08%
Unprotected Insertive Vaginal Sex: ~0.04%
Needle Sharing (IVDU): Varies significantly, but often higher than sexual contact due to direct blood-to-blood contact. (This calculator uses a simplified representation).
Viral Load Adjustment: A simplified adjustment is made. For instance, if the viral load is very high (e.g., >100,000 copies/mL), the baseline risk might be considered higher. If undetectable, the risk is significantly reduced. For this calculator, we use a qualitative adjustment based on typical ranges.
Source HIV Status Adjustment: If the source is unknown, the calculation may default to a moderate risk or assume a higher likelihood based on population prevalence if specific context isn't provided. If known negative, the risk is effectively zero.
Time Factor: While not directly reducing the calculated *risk percentage*, the time factor strongly emphasizes the need for immediate medical consultation for PEP. The calculator highlights this urgency.
Disclaimer: This calculator is an educational tool. It provides estimates and does not constitute medical advice. HIV transmission is complex, and individual risk can be influenced by many factors not included here (e.g., presence of STIs, adherence to PEP). Always consult a qualified healthcare professional for diagnosis, treatment, and management of potential HIV exposure.
Immediate Action: If you have had a potential exposure, seek medical attention immediately. Post-Exposure Prophylaxis (PEP) is a course of HIV medications taken shortly after a possible exposure to prevent infection. It is most effective when started within 72 hours.
function calculateRisk() {
var exposureType = document.getElementById("exposureType").value;
var viralLoadInput = document.getElementById("viralLoad").value;
var sourceHivStatus = document.getElementById("sourceHivStatus").value;
var timeSinceExposureInput = document.getElementById("timeSinceExposure").value;
var resultDiv = document.getElementById("result");
var riskPercentage = 0;
var riskDescription = "";
var urgency = "";
// — Base Risk Probabilities (Estimates from various sources, e.g., CDC, WHO) —
var baseRisks = {
needle_stick: 0.3, // 0.3%
unprotected_sex_receptive_anal: 1.38, // 1.38%
unprotected_sex_insertive_anal: 0.11, // 0.11%
unprotected_sex_receptive_vaginal: 0.08, // 0.08%
unprotected_sex_insertive_vaginal: 0.04, // 0.04%
needle_sharing_ivdu: 0.64 // 0.64% (Can vary widely, this is a general estimate)
};
// — Input Validation —
var viralLoad = parseFloat(viralLoadInput);
var timeSinceExposure = parseFloat(timeSinceExposureInput);
if (isNaN(viralLoad) || viralLoad < 0) {
resultDiv.innerHTML = "Please enter a valid viral load.";
return;
}
if (isNaN(timeSinceExposure) || timeSinceExposure 100000) {
riskPercentage *= 1.5; // Higher viral load increases risk
} else if (viralLoad > 50000) {
riskPercentage *= 1.2; // Moderate viral load increases risk
} else if (viralLoad 10) riskPercentage = 10; // Example cap at 10% for severe cases
// — Determine Urgency based on Time —
if (timeSinceExposure <= 72) {
urgency = "Immediate Medical Attention Required! Seek PEP (Post-Exposure Prophylaxis) within 72 hours.";
} else {
urgency = "It has been over 72 hours. PEP may no longer be effective, but consult a healthcare provider immediately for assessment and guidance.";
}
// — Formulate Result Description —
if (sourceHivStatus === "negative") {
riskDescription = "Based on the information provided, the source is known to be HIV negative, so the estimated risk is 0%.";
} else {
riskDescription = "Estimated Risk: " + riskPercentage.toFixed(3) + "%";
}
resultDiv.innerHTML = riskDescription + "" + urgency + "";
}