PAHO/WHO develops new test for confirming Zika infections

By Benjamin Flowers
Staff Reporter

To aid in Zika virus control efforts, the Pan American Health Organization/World Health Organization (PAHO/WHO) has set new guidelines on how to identify a case of infection.
PAHO/WHO is working with the Arbovirus Laboratory Network (RELDA) and has already agreed on new guidelines using a new algorithm for lab detection which was based on an established regional platform for laboratory surveillance of Dengue. The algorithm was established using 22 national reference laboratories of the RELDA network, and will be able to quickly differentiate between Zika, Chikungunya and Dengue.

While the WHO is working on making mass amounts of the new lab test available, it is also working with experts from the region to develop a tool to help primary care physicians perform differential diagnosis of Zika, Dengue and Chikungunya.
PAHO/WHO’s new guidelines are also to help gather epidemiological data, to learn more about the behaviour of the virus so it can recommend appropriate public health action to fight the disease.

“The best time for laboratory testing for Zika is in the first five days of the onset of symptoms, when PCR tests can detect genetic material [RNA] from the virus,” Jairo Mendez, PAHO’s regional adviser on viral diseases explained. “In that period, test results are more accurate than those made at a later stage where results may be presumptive.”
Currently there are no vaccines or treatment for Zika and the only way to confirm an infection is through a blood test. The testing, however, causes difficulty for health systems because the virus usually circulates in the blood of an infected person for five days or less. While antibodies can be detected for longer periods using other tests, the antibodies to Zika are similar to those of Dengue and yellow fever, which can produce false positives.

Health services have also had a difficult time with identifying and reporting Zika, because 80 percent of those infected will not experience any symptoms at all. Of those that do experience symptoms, many are very mild so patients do not seek medical attention. Of the cases which produce severe symptoms, they are very similar to that of both Chikungunya and Dengue which include: fever and rash, muscle or joint pain. Zika is differentiated by an onset of conjunctivitis (pink eye).

PAHO/WHO said the diagnosis of the Zika virus is important, especially for the care and monitoring of pregnant women because of the possible, but unconfirmed, link between the virus and the birth of babies with microcephaly and the recent suspicion of it causing Guillain-Barre syndrome (a neurological disorder which could end in paralysis.)
Since Brazil first reported cases of Zika in 2015, the virus has spread to 31 countries and territories in the Americas, prompting the WHO to declare the virus a global health emergency. The Ministry of Health in Belize had three suspected cases, however, lab results showed that none were Zika infections. The ministry has been working with all its partners in preparing and executing a national response plan for Zika, emphasizing on prevention and citizen participation.

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