Zika persists for up to thirty days in tears
Zika virus (ZIKAV) seems to persist in the tears and conjunctival swabs of patients 30 days after the illness, reports a new study from Singapore.
Therefore, according to researchers, “[i]t is important to assure that samples of conjunctivae and tears are tested negative for ZIKAV in patients to ensure no risk of virus spread through casual contact.”
Conjunctival swabs were obtained from 29 patients (mean age 40 years) admitted to the Tan Tock Seng Hospital. Patients included had confirmed Zika infection via quantitative reverse-transcription polymerase chain reaction (RT-PCR) of serum and urine samples. Real-time RT-PCR was performed to measure ZIKAV concentration in the swabs.
Of the 29 patients, three patients had conjunctival swabs that tested positive for ZIKAV RNA at 30 days after the illness. All positive samples were from the right eye, and ZIKAV RNA concentrations ranged from 5.2 to 9.3 copies. [Sci Rep 2017;7:11194]
All patients who tested positive were female, with ages ranging from 22 to 47 years, and were of different ethnic backgrounds. All three presented with rashes, while two had conjunctivitis. One patient also had fever and retro-orbital pain in addition to the mentioned symptoms.
“Interestingly, viral load in blood for [one of the positive patients] was moderately high at 19.8 and 272.7 copies during the acute (5 days postillness) and early convalescent (13 days postillness) phases of the infection, respectively, that persisted till late convalescence,” added researchers.
On the other hand, one of the females whose conjunctival samples tested positive had no detectable levels of Zika viral load in the blood and urine.
While it has been proven that Zika persists in body fluids such as blood, urine and semen for a long time after the onset of the illness, this phenomenon has not been reported in tears and conjunctival samples yet, researchers claimed.
The present study is thus the first to show that ZIKAV RNA persists in conjunctival samples for 30 days after illness onset, the longest on record. While transmission of the disease through tears is uncommon, the current findings still warrant caution.
“[T]he important clinical significance of this report is that ocular transmission of the ZIKAV through contact with ocular discharge is potentially possible even up to the late convalescent phase of ZIKAV infection,” said researchers.
Majority (75.9 percent; n=22) of the recruited patients were of Chinese ethnicity. This was followed by the Malay (10.3 percent; n=3) and Indian (10.3 percent; n=3) ethnicities. One patient was from Bangladesh.
The most common presenting symptom was rashes, seen in 96.6 percent (n=28) of the patients. This was followed by fever, present in 69 percent (n=20). Three patients (10.3 percent) experienced eye pain, while eight patients (n=27.5 percent) presented with conjunctivitis, all of whom reported watering and nonpurulent discharge with discomfort.
Zika virus is a flavivirus that is transmitted to humans by a mosquito vector. While it was first discovered in macaque monkeys in Uganda and had its first outbreak in the Western Pacific, it has found its way into the Southeast Asia region. In August of 2016, Singapore had its first local case of Zika transmission. [Trans R Soc Trop Med Hyg 1952:46:509-520; N Engl J Med 2009;360:2536-2543; Euro Surveill 2016;21]