Bats’ immune defenses let the animals safely carry viruses, such as Marburg and Ebola, that can cause deadly outbreaks in people, Erin Garcia de Jesus reported in “Why bat viruses are so dangerous” (SN: 3/14/20, p. 7).
Reader Lori J. Stratton wondered how viruses from bats spread to humans.
Viruses can spill over from bats into people in a variety of ways, says Garcia de Jesus. People can contract Ebola and Marburg by eating infected bats, eating produce contaminated with infected bat saliva or urine, or through other contact with infected bats’ bodily fluids, according to the U.S. Centers for Disease Control and Prevention. The winged mammals also can transmit the viruses to chimpanzees, gorillas, monkeys and other animals, which can then infect people.
Reader Fauzi Saleem wondered if an amino acid from bat milk could be used to treat people with COVID-19. Bats can transmit immune proteins, which are made of amino acids, to offspring through milk.
It’s unclear if bats are the direct source of the new coronavirus, Garcia de Jesus says. Scientists know that the virus came from bats at some point, but it may have taken a detour through another animal first (SN Online: 3/26/20). “Even so, no single amino acid on its own will protect an animal from an infectious disease,” she says. The amino acid must be part of an antibody or another part of the immune response.” Bat antibodies wouldn’t help people because bats’ immune systems are vastly different from the human immune system. “Our immune defenses would probably try to fight off the bat antibodies as well as the virus,” she says.
Science News reporters Tina Hesman Saey, Aimee Cunningham, Jonathan Lambert and Erin Garcia de Jesus are following the latest research to keep you up to date on the coronavirus pandemic. As the virus spreads, the team is answering reader questions about COVID-19.
“Does the initial amount of viral particles inhaled affect the severity of the disease?” reader John Salmon asked.
Researchers are still in the early stages of figuring out whether the number of viral particles that launch an infection influences disease severity. While that appears to be the case for influenza, more research is needed to know if it’s true for COVID-19.
Some preliminary research hints that infected patients who have more virus in their bodies, or higher viral load, over the course of an infection may have more severe disease. Researchers tracking the viral load of patients hospitalized with COVID-19 in Nanchang, China, found that patients with more severe disease had a viral load 60 times as high on average as that of patients with mild cases, the team reported March 19 in the Lancet. But other studies of patients in Italy and China have found no association between viral load and disease severity.
Reader Terry Provost asked about the rates of false-positive and false-negative results for COVID-19 diagnostic tests.
False positives, where someone is told they have the virus but really don’t, are likely rare. Diagnostic tests use a technique called real-time RT-PCR to detect small amounts of the virus’s genetic material. If the virus’s RNA is present in a throat or nasal swab, RT-PCR finds it and amplifies it, resulting in a positive test. If there is no RNA from the virus, there is nothing for RT-PCR to amplify.
False negatives may be more common. One small study, posted online February 17 at medRxiv.org, found that tests that rely on nasal swabs failed to detect the virus in around 30 percent of previously confirmed cases. Throat swab tests failed to detect nearly 40 percent of confirmed cases. When this magazine went to press, the study had yet to be peer-reviewed.
A negative test result does not rule out the possibility of having COVID-19, and any final diagnosis should be made by a clinician.
News you can use
Hundreds of readers have written to Science News about COVID-19. Some people want to know more about the coronavirus. Others have asked about practical steps they can take to reduce their risk of catching it.
Reader Jen Cole wondered how she could disinfect her phone. “So much contradictory information out there,” Cole wrote.
A household cleaning wipe that has at least 70 percent isopropyl alcohol will work, says molecular biology and senior writer Tina Hesman Saey. Avoid bleach and spraying products directly on your phone, as that may introduce too much moisture.