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article imageDormant viruses reactivate during spaceflight

By Karen Graham     Mar 18, 2019 in Science
Herpes viruses reactivate in more than half of crew aboard Space Shuttle and International Space Station missions, according to NASA research, presenting yet another physiological problem for scientists to solve before we journey out into deep space.
Besides the technical hurdles to overcome before humans can travel to Mars or even colonize our close neighbor, the moon, there are also health challenges that astronauts may face after being in space for prolonged periods of time.
Besides the effects of weightlessness, slowing of cardiovascular system functions, decreased production of red blood cells, balance disorders, and eyesight disorders, researchers have also been studying how prolonged periods in space can change the immune system.
In a recent NASA-funded study published in the peer-reviewed journal Frontiers in Microbiology, scientists found dormant viruses can reactivate in the human body during spaceflight, with four of the eight known human herpes viruses detected.
An astronaut goes on a spacewalk outside the International Space Station  where he may soon be joine...
An astronaut goes on a spacewalk outside the International Space Station, where he may soon be joined by tourists
The researchers found that while a small number of the astronauts developed symptoms, virus reactivation rates increase with spaceflight duration and could present a significant health risk on missions to Mars and beyond, reports
"NASA astronauts endure weeks or even months exposed to microgravity and cosmic radiation – not to mention the extreme G forces of take-off and re-entry," says Satish K. Mehta from the Johnson Space Center, and senior author on the new study.
"This physical challenge is compounded by more familiar stressors like social separation, confinement, and an altered sleep-wake cycle."
In order to study the physiological effects of spaceflight, the researchers analyzed saliva, blood and urine samples collected from astronauts before, during and after spaceflight.
The Epstein–Barr virus (EBV)  also called human herpesvirus 4 (HHV-4)  is one of eight known virus...
The Epstein–Barr virus (EBV), also called human herpesvirus 4 (HHV-4), is one of eight known viruses in the herpes family, and is one of the most common viruses in humans.
Liza Gross
The scientists found that there is a rise in the secretion of stress hormones like cortisol and adrenaline during spaceflight. These hormones are known to suppress the immune system. "In keeping with this, we find that astronaut's immune cells—particularly those that normally suppress and eliminate viruses—become less effective during spaceflight and sometimes for up to 60 days after,"{ Mehta said.
It is during this phase of increased stress that dormant viruses reactivate and resurface. "To date, 47 out of 89 (53%) astronauts on short space shuttle flights, and 14 out of 23 (61%) on longer ISS missions shed herpes viruses in their saliva or urine samples," reports Mehta, according to New Atlas.
Epstein–Barr virus (EBV), varicella-zoster virus (VZV), and herpes-simplex-1 (HSV-1) were all found to have reactivated and shed into saliva and urine samples in more than half of the studied astronauts. In most cases, the astronauts did not develop and specific symptoms, but during prolonged space flights, this could be a problem.
"These frequencies—as well as the quantity—of viral shedding are markedly higher than in samples from before or after a flight, or from matched healthy controls."
Risks to immunocompromised individuals
Only six astronauts showed any symptoms due to the reactivation of the viruses, and all of them were minor. However, the study found that "continued virus shedding post flight could endanger immunocompromised or uninfected contacts on Earth, like newborns. Infectious VZV and CMV were shed in body fluids up to 30 days following return from the International Space Station."
Herpes simplex lesion of lower lip  second day after onset
Herpes simplex lesion of lower lip, second day after onset
And herein lies the challenge - Longer spaceflights, like a mission to Mars, will require that we develop countermeasures to virus reactivation. Mehta says, "The ideal countermeasure is vaccination for astronauts—but this is so far available only against VZV."
Trials of other herpes virus vaccines show little promise, so our present focus is on developing targeted treatment regimens for individuals suffering the consequences of viral reactivation."
The human herpes viruses
Eight major herpes viruses parasitize humans with worldwide infection rates of 70–95 percent. Five of the viruses are extremely widespread among humans, with more than 90 percent of adults having been infected with at least one of these. After the initial infection, the viruses stay in the body but become dormant.
Various viruses from the Herpesviridae family seen using an electron micrograph Amongst these member...
Various viruses from the Herpesviridae family seen using an electron micrograph Amongst these members is varicella-zoster (Chickenpox), and herpes simplex type 1 and 2 (HSV-1, HSV-2).
The human herpes viruses are as follows:
HHV-1 - Herpes simplex virus-1 (HSV-1) causing Oral and/or genital herpes (predominantly orofacial), as well as other herpes simplex infections.
HHV-2 - Herpes simplex virus-2 (HSV-2) causes oral or genital infections, primarily genital.
HHV-3 - Varicella-zoster virus (VZV) causes Chickenpox and shingles.
HHV-4 - Epstein–Barr virus (EBV), lymphocryptovirus. This virus is responsible for Infectious mononucleosis, Burkitt's lymphoma, CNS lymphoma in AIDS patients, post-transplant lymphoproliferative syndrome (PTLD), nasopharyngeal carcinoma, HIV-associated hairy leukoplakia.
HHV-5 - Cytomegalovirus (CMV). Causes Infectious mononucleosis-like syndrome, and retinitis.
HHV-6A and 6B - Roseolovirus, Herpes lymphotropic virus. Causes Sixth disease (roseola infantum or exanthem subitum)
HHV-7 - No known name, but it targets T-Cells. This virus causes a drug-induced hypersensitivity syndrome, encephalopathy, hemiconvulsion-hemiplegia-epilepsy syndrome, hepatitis infection, postinfectious myeloradiculoneuropathy, pityriasis rosea, and the reactivation of HHV-4
HHV-8 - Kaposi's sarcoma-associated herpesvirus (KSHV), a type of rhadinovirus. This virus is responsible for Kaposi's sarcoma, primary effusion lymphoma, and some types of multicentric Castleman's disease.
More about herpes viruses, Spaceflight, Astronauts, reactivation, physiological problem
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