VIRAL DISEASES: H7N9 BIRD FLU
China is undergoing its worst epidemic of human cases of H7N9 bird flu since the virus’s discovery in 2013, some 460 cases between last October and February of this year. Most human patients are seriously ill, and 40% have died.
Nearly all human cases have occurred after exposure to infected poultry, according to the Centers for Disease Control and Prevention. Human-to-human transmission of the virus is currently possible but rare.
H7N9 has already undergone genetic changes that have made it more pathogenic for birds. Public health officials worry that additional mutations could make it more transmissible between people, according to Lena Sun at To Your Health. CDC is working on a vaccine. At MedpageToday, Michael Smith says recent genetic changes in H7N9 could have boosted its ability to resist antiviral drugs such as Tamiflu, although the changes might also have resulted from the therapy.
H7N9 has not yet been detected in the US. The World Health Organization says current risk of a pandemic is low. But public health authorities think the risk could be much higher in the next few years. Julia Belluz walks us through the reasons why at Vox. First, Trump has not yet filled the job of CDC director, and the agency’s budget is likely to be cut. Belluz thinks the “America First” mindset and border restrictions likely also contribute to heightened risk.
VIRAL DISEASES: ZIKA
Being bitten by a mosquito carrying the Zika virus usually causes mild illness, and often no noticeable symptoms at all. But Zika virus infection during pregnancy is a different matter entirely. It can cause birth defects, especially the otherwise rare head and brain deformity called microcephaly.
Now the CDC has quantified the risk. The agency says the rate of birth defects in children born to Zika-infected mothers is 20 times higher than normal, Julie Beck reports at The Atlantic. She says it’s clear that the cohort of babies being born now in the US will have abnormally high rates of microcephaly. The normal rate is 7 cases per 10,000 births.
It turns out that Zika is not always a benign infection in adults, either. It is now suspected of causing heart failure and atrial fibrillation as a result of a small study in Venezuela, according to Crystal Phend at MedPageToday. The study needs confirmation with larger samples, of course. But heart problems can be a consequence of other viral infections, such us dengue, so they wouldn’t be too surprising in Zika infection.
Zika also appears to hit some patients a lot harder than others. At Motherboard, Kate Lunau describes a study of Canadian travelers that found higher rates of complications–including devastating Guillain-Barré Syndrome–from Zika virus infection than from dengue.
VIRAL DISEASES: HERE COMES YELLOW FEVER?
And that’s not all. At Ars Technica, Beth Mole says that unusually active outbreaks of yellow fever are occurring in rural Brazil. She quotes an alarmed Wednesday commentary in the New England Journal of Medicine from scientists at the National Institute of Allergy and Infectious Diseases, Catharine Paules and Anthony Fauci.
Paules and Fauci are worried that the virus could spread quickly, including to the US, if it moves from its current hosts, forest mosquitoes, into the ubiquitous Aedes aegypti. They say, “As we have seen with dengue, chikungunya, and Zika, A. aegypti–mediated arbovirus epidemics can move rapidly through populations with little preexisting immunity and spread more broadly owing to human travel.”
Mole points out that there’s a big difference between yellow fever and the other viruses, like Zika, that are carried by Aedes aegypti. It’s far more deadly. There’s a little-used vaccine, and treatment is symptomatic only. If yellow fever emerged in the US, it would be the first time in more than a century.
DENISOVAN SKULLS IN CHINA?
Paleoanthropologists have identified several of our forebears by examining their fossilized bones. But there’s one human ancestor known essentially only from DNA. The DNA was extracted from a fragment of a young girl’s pinky bone and big wisdom teeth from two men.
These fragments turned out to be from a previously unknown but distinct human group that we’ve been calling Denisovans because they were preserved for 21st century examination by the very cold Denisova cave in the Altai mountains of Siberia. The pinky fragment and teeth are all that has been found of these enigmatic people.
All that has been found so far. The possibility is not mentioned in the paper itself, but there’s some hope that two partial skull caps from China reported on in the March 2 Science might show us something of what the Denisovans looked like.
Philipp Gunz, an evolutionary anthropologist at the Max Planck Institute in Leipzig, told Ben Guarino at the Washington Post that the skull pieces “certainly look like what many paleoanthropologists (myself included) imagine the Denisovans to look like.”
DNA could settle the matter immediately. But attempts to extract DNA from the skull fragments have so far failed, according to Ann Gibbons at Science. The skulls possess prominent brow ridges that are Neandertal-like but thinner. One of these humans had a huge brain, at 1800 cc as large as the largest Neandertal and modern human brains.
The Denisovans mated with both the Neanderthals and modern humans, which makes them Homo sap‘s direct ancestor. One of many, as it turns out. The scientists who found them say the Chinese crania display a mixture of Neandertal and modern human traits, according to Annalee Newitz at Ars Technica.
Some of today’s East Asians possess about 1% of Denisovan DNA. Larger amounts are found among people living on islands of Southeast Asia and Oceania, according to Bridget Alex’s recent Discover feature. (This is a useful roundup of what’s known about the Denisovans, and also contains a terrific clear graphic illustrating the timeline of human evolution beginning about 4 million years ago.)
The Chinese skull fragments have been dated at between 105,000 and 125,000 years ago, making them a little older than the Denisova cave finds. They were excavated at the Lingjing site in China’s Henan Province between 2007 and 2014, Seth Augenstein notes at Laboratory Equipment.
Senior author Erik Trinkaus, Washington University in St. Louis, appears to be a lumper, not a splitter. He resists the notion that the Chinese finds should be labeled “Denisovan.” “What we’re talking about is a unified humanity, and a modest level of diversity on top of that,” he told Augenstein. “The parallel that has been said by anthropologists over and over and over again is that, distinct races do not exist in modern humanity – we only see clear contrasts when we look at people from very different parts of the world and the modern dispersal nature emphasizes those.”