New Zika Serotypes May Emerge, Researcher Warns
SÃO PAULO, Brazil -- October 10, 2017 -- Zika virus is mutating so fast in Brazilian patients that different serotypes of the pathogen could appear in the near future, as is already the case with dengue virus.
This would hinder the production of a vaccine and impair the effectiveness of the diagnostic tests already developed.
The alarm was sounded by Edison Luiz Durigon, University of São Paulo's Biomedical Science Institute (ICB-USP), São Paulo, Brazil.
Such assertion is based on a study carried out by a group of scientists from the institute under the auspices of the Zika Virus Research Network in São Paulo (Rede Zika), which is supported by the São Paulo Research Foundation (FAPESP).
“Today there's only one Zika, and people become immune after being infected once,” said Durigon. “But the virus is constantly mutating, and I wouldn't be surprised if we see Zika 2, 3, and 4 emerging before long.”
For months, the team closely monitored 3 asymptomatic patients (2 men, 1 woman) and collected samples of the patients' blood, saliva, and urine, as well as semen in the men, every week. The material was sent to the United States, where whole-genome sequencing of the virus was performed thanks to a partnership with the US Army.
"Week by week, we examined the data to see what was different in the viral genome,” Durigon said. “In one patient, we found compartmentalised strains -- the virus present in his semen was different from the virus in his urine. In all cases, the pathogen we found in the final stage of the infection wasn't the same as the virus that entered the patient.”
According to Durigon, the male patients continued to excrete large amounts of Zika virus in their semen for up to 6 months. One was found to have the virus in his saliva for 3 months.
“Zika continued to replicate in the patient’s testicular cells all this time, and using an electron microscope, we could see that the spermatozoa were formed already infected,” he said. “This means a conception could occur with infected sperm. We have no idea whether pregnancy progresses in such cases, and if so, what the consequences would be for the fetus.”
The possibility of sexual transmission greatly increases Zika virus’s capacity to spread, Durigon added, stressing that in his view, medical culture must change, as the profession still focuses on antenatal care for women.
“It's no use testing only pregnant women to see if the virus is present, and advising only women to use insect repellent and avoid high-risk areas during pregnancy, while leaving men to go on with their lives as normal,” he said. “Women could be infected by their partners. Doctors aren't paying attention to this possibility.”
“After 2 years, we can at last say with pride that we’ve produced a genuinely effective serological test to detect Zika," Durigon said. "We've validated it in over 1,000 samples from the population of São José do Rio Preto in the interior of São Paulo State, and in 800 samples from patients in Salvador, Bahia, including women who had children with and without microcephaly and patients who had yellow fever and dengue. If this test can identify Zika in Salvador, it can work anywhere in the world.”
The next step is to collect more samples in São Paulo State and its capital in order to find out how many people have actually been infected to date in the region. Because up to 80% of cases may be asymptomatic, without the serological test, it is impossible to know the real magnitude of the epidemic and the percentage of the population that is still susceptible to the virus.
As soon as the serological test is available on a large scale, the largest possible number of children born during the period should be tested. Positive results should be assessed with caution and confirmed by imaging.
“What we're seeing is just the tip of the iceberg,” said Durigon. “We don’t know what's underneath.”
SOURCE: São Paulo Research Foundation