Commercial blood test
The diagnosis of pregnant travellers worried a Zika infection upon their return home was cited as one example. Waiting for a diagnosis is just a few hours.
Researchers at the University Hospital, Freiburg and at the Bernhard Nocht Institute for Tropical Medicine have now substantiated the use of a commercial blood test for antibodies. ‘This test detects Zika virus antibodies reliably and, unlike other procedures, shows no cross reactivity with other, related viruses,” confirmed Dr Daniela Huzly, head of Diagnostics at the Institute of Virology in Freiburg. Professor Thomas Mertens, President of the Society for Virology, added: ‘The availability of a reliable and fast test for the specific and sensitive detection of Zika virus antibodies is a great relief for those who may be infected as well as for doctors.’
A small window of time
In a patient with an acute infection the Zika virus has generally been confirmed via direct virus detection, a so-called PCR test. However, diagnosis is only possible during a small window of time and only works during the first few days of an infection. Most patients therefore require a serological examination, i.e. a test for antibodies.
One problem with this is that the antibodies developed by the body against the Zika virus show a distinct cross reactivity with antibodies against related viruses in most of the previously used blood tests. Thus a test reacts positive when antibodies against other viruses circulate in the blood, such as those against FSME, Yellow fever or Dengue fever. This is a problem not only for those already infected but also those previously vaccinated against one of these viruses.
Ascertaining whether a patient really is infected with the Zika virus therefore required further, extensive tests that can only be carried out in a few specialist laboratories. The new test, however, does not require extensive diagnostics and can be carried out in any laboratory that routinely tests for antibodies.
Also test men with pregnant wives
The Society for Virology and the Bernhard Nocht Institute for Tropical Medicine recommend confirming a potential Zika virus infection not only for pregnant travellers returning from locations where the Zika virus has spread, but also for men who have spent time in those areas and have pregnant partners. In both cases testing is also recommended when no symptoms or illness are present.
Returning travellers who had symptoms typical of a Zika virus infection, such as fever, headache, lethargy, muscle and joint pains, rash, conjunctivitis, can also be tested to check whether they are infected, even when symptoms may have been mild.
Source: Society for Virology, http://g-f-v-org/newsletter