Urine Sample Better Test Than Serum Test in Zika Virus Patients

Urine samples can successfully be used for the detection of the Zika virus (ZIKV), a mosquito borne pathogen, according to a study published in Emerging Infectious Diseases.

Researchers from the Institut Pasteur in New Caledonia investigated the diagnostic utility of urine as a source for detection of ZIKV RNA by real-time reverse transcription PCR (RT PCR). Previously, confirmation of ZIKV infection is based on detection of virus RNA in serum by using RT PCR.

In humans, ZIKV manifests in the form of a mild fever, arthralgia in small joints like hands and feet, myalgia, headache, retro-orbital pain, conjunctivitis, and cutaneous maculopapular rash. The disease is often asymptomatic or mildly symptomatic in most cases. However, because of this it is often also misdiagnosed. It is believed to be transmitted to humans by infected mosquitoes, and was isolated in 1947 from a rhesus monkey in the Zika forest in Uganda. An epidemic of ZIKV occurred in the South Pacific region in 2007, leading researchers to determine that ≤70 percent of the region had been infected.

The clinical symptoms of 6 ZIKV patients were recorded, including maculopapular rash of the trunk and extremities. A blood count demonstrated discreet perturbation common in many viral infections like mild leucopenia and thrombocytopenia associated with activated lymphocytes.

In order to detect ZIKV in samples, 2 sets of primers/probes specific for ZIKV were used. The blood samples were tested for dengue virus and chikungunya virus by real time RT PCR and showed negative results. ZIKV virus was initially detected in 4 out of the 6 patients in which symptoms were demonstrated. Then, urine samples from 2 other patients were also ZIKV positive, and showed a higher viral load than corresponding serum samples. To compare, the researchers tested urine samples from 6 healthy patients and found no detection of ZIKV.

The researchers commented that because ZIKV is primarily benign and poorly described, the infection has likely been underdiagnosed and underreported in disease endemic settings or in returning travelers.

“ZIKV was detected in patient serum until a rash was observed (days 2-3 after disease onset),” the authors wrote, while noting that future studies into this topic would likely evaluate whether live infectious ZIKV are excreted in patients’ urine to observe for other arboviruses. “However, urine was preferred for virus detection. We observed a slight increase in ZIKV RNA from urine over the first few days after disease onset and rash.”

Though it was a small sample of ZIKV positive patients, the results suggest that urine would be useful in ZIKV positive confirmation because the virus was detected at higher levels and for a longer duration than in serum samples, the authors concluded.