- The news comes on a day Kenya confirmed its second Mpox case, sparking fresh fears about the spread of the disease within the country.
- Health CS Deborah Mulongo said he is a male truck driver screened at the Malaba One Stop Border Post in Busia county.
Image: CDC
The Africa Centre for Disease Control has written to Health ministers in AU member states, warning that a negative Mpox laboratory test is not a guarantee that the virus is absent in a sample.
The news comes on a day Kenya confirmed its second Mpox case, sparking fresh fears about the spread of the disease within the country.
The male truck driver was screened at the Malaba One Stop Border Post in Busia county.
Africa CDC Director General Dr Jean Kaseya said 13 African Union member states have so far reported 21,466 cases (3,350 confirmed; 18,116 suspected) and 591 deaths with a case fatality rate (CFR) of 2.9 per cent.
According to Dr Kaseya, the confirmed cases and deaths could just be the tip of the iceberg, considering Mpox is not 100 per cent detectable through lab tests.
“I would like to draw your Excellencies' attention to the fact that a negative test result in the laboratory does not mean there is no Mpox epidemic,” Kaseya said.
He said the conclusion was arrived at after consultations with Africa’s best epidemiologist and lab experts, as well as international experts and appropriate bodies like US CDC, China CDC, Europe CDC and WHO.
“The conclusion is that relying solely on laboratory test results for diagnosing Mpox is not advisable. It can sometimes yield a negative result in the laboratory even when the disease is present due to several factors,” the DG said.
Why Mpox lab test result can be false
According to Kaseya, there are six factors which can cause an Mpox lab test to yield a negative result even when the disease is present.
Timing of Sample Collection: The accuracy of Mpox testing depends significantly on when the sample is collected. If the sample is taken too early or too late in the course of the infection, the viral load might be too low to be detected.
Type of Sample Collected: The type of sample collected (e.g. from a lesion, blood, or other bodily fluids) can affect the test results. Lesion swabs are typically the most reliable, but if a different type of sample is used, it may not contain enough viral material for detection.
Quality of the Sample: Poor sample collection techniques can lead to inadequate samples, resulting in a false negative. This might include improper handling, storage, or contamination of the sample
Test Sensitivity and Specificity: No test is perfect, and some Mpox tests may have lower sensitivity, meaning they might not detect very low levels of the virus. This can result in a false negative if the viral load in the sample is below the test's detection threshold.
Viral Variability: Different strains or mutations of the Mpox virus might not be as easily detected by certain tests, especially if the tests were designed for a specific strain.
Host Immune Response: In some cases, an individual's immune system might clear the virus or suppress its replication to levels undetectable by laboratory tests, even though the disease was present.
Dr Kaseya said the continent needs a holistic approach that integrates laboratory testing with clinical assessment and epidemiological data that is essential for accurately diagnosing and managing Mpox.
Accurate Mpox diagnosis
The DG said accurate diagnosis of Mpox should involve a comprehensive approach that considers multiple factors.
These include clinical presentation: The signs and symptoms of Mpox, such as fever, rash, swollen lymph nodes and lesions.
Epidemiological Context: Understanding the patient’s exposure history, such as contact with known cases or travel to areas.
History and Risk Factors: Reviewing the patient’s medical history, including any recent exposure to animals or contaminated materials.
Laboratory Testing: While important, lab tests should be interpreted in conjunction with clinical and epidemiological data. A negative test does not entirely rule out Mpox.
Follow-up and Monitoring: Continuous monitoring of the patient’s symptoms and possibly repeating tests can help in making a definitive diagnosis.
Differential Diagnosis: Other conditions with similar symptoms (like chickenpox, measles, or bacterial skin infections) should be considered and ruled out.
The Africa CDC declared Mpox a Public Health Emergency of Continental Security (PHECS) on August 13, 2024.
A day later, the World Health Organization declared the disease a Public Health Emergency of international Concern (PHEIC).