Ecological Tradeoff? A study is the first to document the While the exact cause remains unclear, the researchers found that more shark attacks than average occur during Chewing is also known to help prevent obesity, possibly by increasing the thermic effect of food consumption. But the factors behind this heat-generating effect of It is possible to bypass methanogenesis with the seemingly simpler and more environmentally friendly This changes our understanding of evolution and could one day help researchers breed better crops or even help humans fight But a new study shows Australia's Tasmanian devils have their own The work identifies the CLSY genes as major factors underlying epigenetic For You Children Patient Handouts.
What is respiratory syncytial virus RSV? How is respiratory syncytial virus RSV spread? RSV spreads from person to person through: The air by coughing and sneezing Direct contact, such as kissing the face of a child who has RSV Touching an object or surface with the virus on it, then touching your mouth, nose, or eyes before washing your hands People who have an RSV infection are usually contagious for 3 to 8 days.
Who is at risk for respiratory syncytial virus RSV infections? Certain people are at higher risk of having a severe RSV infection: Infants Older adults, especially those age 65 and older People with chronic medical conditions such as heart or lung disease People with weakened immune systems What are the symptoms of respiratory syncytial virus RSV infections?
The symptoms of RSV infection usually start about 4 to 6 days after infection. They include: Runny nose Decrease in appetite Cough Sneezing Fever Wheezing These symptoms usually appear in stages instead of all at once. How are respiratory syncytial virus RSV infections diagnosed? Your health care provider may use many tools to make a diagnosis: A medical history, including asking about symptoms A physical exam A lab test of nasal fluid or another respiratory specimen to check for RSV.
This is usually done for people with severe infection. Tests to check for complications in people with severe infection. The tests may include a chest x-ray and blood and urine tests. It has often been questioned whether a virus is alive. It is certainly not living in the everyday sense of the word. Many viruses, called enveloped viruses, have an additional outer membrane that encloses the protein coat. Enveloped viruses are then free to begin a new cycle of infection by fusing their cell-derived envelope with the cellular membrane of an uninfected cell.
In either case, the genetic material of the virus has invaded the cell through the barrier of its membrane, and infection will inevitably follow Fig. Infection can be prevented if fusion of the viral envelope with the cell or endosomal membrane can be blocked. Similarly, if a vaccine can be directed against the viral fusion protein, infection can be prevented. Vaccines against the influenza virus, for example, target the fusion proteins of the virus. Viral entry pathways. Virus can fuse either directly to the plasma membrane receptor-mediated fusion or after being swallowed into an endosome.
Which of these routes is followed depends on the type of virus. In fusion with the plasma membrane, the virus binds to a protein in the cell membrane. The function of this cellular protein a receptor for the virus, shown in green is perverted to induce a conformational change in the viral fusion protein, leading to fusion.
In either case, the viral genome passes through a fusion pore into cytosol, and infection is initiated. To see this figure in color, go online. Viral genetic material is relatively small, encoding only a few proteins. All enveloped viruses contain fusion proteins, which are the molecules responsible for fusing the envelope to a cellular membrane.
The precise genetic material, the amino acid sequence, and details in structure of a fusion protein are unique for each type of virus.
Consequently, broad-spectrum antiviral drugs do not exist, and specific vaccines and drugs typically need to be developed for each virus type. The viral surface of an individual virion contains multiple copies of its fusion protein. Influenza virus, for example, typically contains — copies, whereas HIV contains only about a dozen copies 1 , 2.
Because enveloped viruses use similar mechanisms for delivery of genetic material into cells, there may be ways to prevent infection before viral entry that would be effective for large numbers of different viruses. The membrane that is the skin of a cell and an enveloped virion, and is the gateway of viral entry, consists of lipids and proteins. Lipids are roughly linear molecules of fat that are attached at one end to a water-soluble headgroup. Lipids provide the cohesion that keeps biological membranes intact.
They spontaneously arrange themselves into a lipid bilayer because oily fat does not mix with water. The headgroups of one monolayer face an external aqueous solution, whereas the headgroups of the other monolayer face the interior of the cell.
Integral membrane proteins, such as viral fusion proteins, are inserted into the bilayer and project out from the lipid surface into the external solution-like icebergs. Membranes are able to fuse to each other because they are fluid 3 , and the lipids provide fluidity to the membrane. Viruses initially stick to cell membranes through interactions unrelated to fusion proteins.
The virus surfs along the fluid surface of the cell and eventually the viral fusion proteins bind to receptor molecules on the cell membrane 4. If only binding occurred, the two membranes would remain distinct. Fusion does not happen spontaneously because bilayers are stable.
Fusion proteins do the work of prodding lipids from their initial bilayer configuration. These proteins cause discontinuities in the bilayers that induce the lipids of one membrane e. Fusion proceeds in two major steps Fig.
In the second step, the fusion proteins disrupt this single bilayer to create a pore that provides an aqueous pathway between the virus and the cell interior. It is through this fusion pore that the viral genome gains entry into a cell and begins infection. The steps of fusion. Virus binds to specific receptors each illustrated as a small cactus on a cell membrane. Initially, four monolayers in blue separate the two interior aqueous compartments. After fusion peptides insert into the target membrane, monolayers that face each other merge and clear from the merged region.
The noncontacting monolayers bend into the cleared region and come into contact with each other, forming a new bilayer membrane known as a hemifusion diaphragm. At this point hemifusion , only two monolayers separate the compartments. The fusion protein acts as a nutcracker to force the formation of a pore within the hemifusion diaphragm. This establishes continuity between the two aqueous compartments and fusion is complete. Hemifusion and pore formation appear to require comparable amounts of work, but the exact amount of energy needed for each step is not yet known 5.
These energetic details may be important because the more work required to achieve a step, the easier it may be to pharmacologically block that step. It can also be spread through smaller virus-containing particles that remain in the air over longer distances and time, according to the Centers for Disease Control and Prevention. Nearly 23 million eligible children have received at least one dose of the coronavirus vaccine since the most recent group of 5-toyear-olds got the green light late last year and started rolling up their sleeves.
But many families are anxiously awaiting a pediatric vaccine for the youngest Americans — ages 6 months through 4 years — as the omicron variant surges across the United States. Federal health officials said Wednesday that the United States has agreed to buy hundreds of thousands of doses of a covid treatment developed by drugmaker AstraZeneca. AstraZeneca officials cheered the news. The Food and Drug Administration issued an emergency-use authorization last month for Evusheld, an antibody cocktail designed to help prevent covid in immunocompromised people.
It is authorized only for those who have a moderate to severely compromised immune system or a history of severe adverse reactions to the coronavirus vaccines or their components.
Officials hope the drug can serve as an alternative prevention option for those whose immune systems are unable to mount an adequate response to the vaccines, as well as those who cannot take them. Zients touted the treatment as one of several the U. The Biden administration is weighing making high-quality masks more widely available, officials said Wednesday, as some experts urge the Centers for Disease Control and Prevention to recommend KN95 and N95 masks amid the case surge driven by the highly transmissible omicron variant.
Speaking at a news briefing, White House coronavirus response coordinator Jeffrey Zients said the CDC continues to recommend that well-fitting masks be worn in indoor public settings.
That could include multiple-layered cloth masks, N95s or KN95s, he added. The seven-day average of cases in the country is about , per day, up about 47 percent from last week, according to figures released during the briefing.
The seven-day average of hospital admissions is about 19, per day, an increase of about 33 percent over the previous week. The seven-day average of deaths is about 1, per day, about 40 percent higher than the previous week — though health authorities attribute that increase to the delta variant. CDC Director Rochelle Walensky said at the briefing that the agency is updating its website to provide more information on the types of masks and the protection they offer.
She added that the best mask is one a person can tolerate wearing when needed. Some of the culprits for this round of shortfalls are the same as in the early days of the pandemic, and some can be chalked up to new problems bumping up against old ones. Here are some of the reasons an array of your favorite items may be out of stock at grocery stores: Read the full story. And wiggled. West Virginia Gov. He added that his wife, first lady Cathy Justice, tested negative. A health official gathering information from people at a drive-through coronavirus testing site in Houston last week discovered what appeared to be a child inside the trunk of one of the vehicles.
The driver of the vehicle, Sarah Beam, a year-old high school teacher, confirmed that her year-old son was in the trunk, according to the health official. Beam said her son had tested positive for the coronavirus, so she put him in the trunk to avoid exposure on her way to the site to have him tested again, the official said. Beam is facing a felony charge of endangering a child, according to court records.
Beam did not immediately return a message seeking comment late Monday, and court records do not list her attorney. She is due in court Thursday. As the omicron variant threatens the halls of Congress and some GOP lawmakers continue entering the House chamber maskless, despite racking up tens of thousands of dollars in fines, Assistant House Speaker Katherine M.
Clark D-Mass. In a letter to the House sergeant-at-arms on Tuesday, Clark requested that lawmakers who flout the mask mandate be cordoned off in a plexiglass-enclosed section in the House gallery to help protect other members from exposure to the coronavirus.
New Orleans will reinstitute an indoor mask mandate in an attempt to curb the highly contagious omicron variant as the city prepares for Mardi Gras visitors. Starting 6 a. Avegno said the mandate would also apply to participants in the annual Mardi Gras balls that take place in the city. Mardi Gras — also known as Fat Tuesday — falls on March 1 this year.
But parades, which draw large crowds of locals and visitors to city streets, begin in the last two weeks of February.
0コメント