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队友们，4月16日周二的科技作业来了，大家加油哦。
另，标题用的是白色字体，选择就可以看到了。
Part I Speed
Artile I (Check title later)
Steady Increase in China's H7N9 Cases: Media Reports 38 Cases, 10 Deaths 【Time1】
At the time of this posting, the official WHO count remains at 33 cases and 9 deaths, but Chinese media reports 38 H7N9 cases and 10 deaths. The newest cases are from Shanghai (three cases and one death) and Jiangsu (two cases). HealthMap, along with several other disease surveillance groups, bloggers, scientists, and officials, has been closely following the outbreak as it unfolds.
The cases are geographically clustered in eastern China: Shanghai (18 cases and 6 deaths), Jiangsu Province (12 cases, 1 death), Anhui Province (2 cases, 1 death) and Zhejiang Province (6 cases and 2 deaths). The five cases reported this morning are from Shanghai, Jiangsu and Zhejiang Provinces.
Chinese media reports that genetic reassortment between wild birds from “east Asia” and chickens from “east China” are the source of the virus. The finding from scientists in Shenzen eliminates pigs as a potential host.
If this is true, the geographic spread makes some sense, at least according to Declan Butler. In a recently published piece in Nature, Butler explains that birds at live poultry markets in China arrive from a variety of sources and each source may send its birds to different markets. Butler also states that officials have found evidence of H7N9 in pigeons, ducks and chicken at live poultry markets in Shanghai and Hangzhou. As a result, live poultry markets in Shanghai, Nanjing and Hangzhou have been shut down and thousands of birds have been culled.
Among the most concerning characteristics of this virus are that it is a completely new virus in humans, so we do not have any immunity against it, and that it has adapted to infect mammal cells. So how can we protect ourselves against it?
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【Time2】
The New York Times recently reported that the CDC was participating in the production of a seed vaccine (meaning a vaccine made from a laboratory-produced virus) to protect against H7N9. In a press briefing on April 5, CDC Director Dr. Tom Frieden explained that vaccine manufacturing was out of “an abundance of caution,” and that it would only be produced if there is evidence of human-to-human transmission.
As Declan Butler writes, this is indeed the question that is on everyone’s minds: will the “novel avian influenza virus […] rapidly fizzle out, become established in animal hosts to fuel future human outbreaks, or morph into a virus that can spread easily between people and spark a deadly pandemic.”
For the time being, there is no evidence of human-to-human transmission. The WHO is sending out 140 character reassurances via Twitter. In fact, last week, the WHO announced that it would be publishing updates on Twitter first, and in press releases after. That the WHO is tweeting these statements is significant; it suggests an acknowledgement of the important of social media in disease detection and response.
There is some good news to be gleaned from using online data sources for disease surveillance. A HealthMap research fellow has been studying flu-related searches on Chinese search engine Baidu in relation to influenza cases. He has found a meaningful correlation between seasonal influenza and influenza-related searches on Baidu based on the past four years of data. Using these methods on recent data, he found a spike in searches this April, after the breaking news on the first H7N9 cases. The absence of an increase in flu-related searches before the H7N9 news broke indicates that there has not been an undetected surge in cases prior to the official announcement. While deducing true disease incidence from measurement of human behavior is an imperfect science, research in the past has demonstrated utility in this approach (Google Flu Trends, for example). As epidemiologists cautiously watch this outbreak develop, we welcome this bit of good news.
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Article II (Check title later)
Coronavirus Steals Media Spotlight with Promising New Research 【Time3】
Amidst all the articles on H7N9 in China, the novel coronavirus (nCoV) is making headlines again. While the number of cases continues to trickle upward, there has been rapid progress in developing tools for monitoring, detecting and researching the virus, leaving the public health community feeling slightly more prepared for what this virus may bring.
The virus itself has raised concern because it is from the same family of viruses as SARS, a respiratory virus that caused global concern in 2003. SARS ultimately infected over 8,000 people and killed around 750. While the novel coronavirus is still under investigation, and cannot be classified as “SARS-like,” scientists warn that nCoV still has pandemic potential.
So far there have been 17 cases of nCoV, 11 of which have been fatal. The latest death was an Emerati man who died in a German hospital. He followed a trend: all of the cases have links to countries in the Middle East like Jordan and Saudi Arabia. Two cases had mild symptoms, appearing like a common cold. Since colds are usually mild and self-limited (i.e. go away without medical intervention), there are an unknown number of undiagnosed mild cases.
A number of reference laboratories have developed antibody tests (antibodies are proteins in the blood that look for and neutralize pathogens) for nCoV, giving clinicians the ability to determine who has been exposed to the virus. The presence of certain antibodies indicates that specific pathogens are or were present somewhere in the body.
The new serologic tests (tests looking for antibodies in bodily fluids) will help to identify more infected people, regardless of whether the symptoms are mild or severe. This will ultimately help clarify the ratio of severe to mild cases and give an indication of how efficiently the virus spreads. While human-to-human transmission has occurred, it seems as though this is not an efficient method of transmission for the virus as the latest patient who died in Germany passed away without infecting any of 60 potential contacts.
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【Time4】
Much research remains to be done, however, as it is still unclear whether the detected cases represent the extent of the disease or if there are larger reservoirs of mild disease. Scientists in Germany have agreed to work with partners in the United Arab Emirates to extend capacity in laboratories there. A wider distribution of testing will help ensure the broadest surveillance network to determine the true extent and severity of this novel illness.
Most recently, scientists announced they have developed an animal model for the disease, using rhesus macaques, permitting more clinical studies and vaccine research. An animal model is useful because it allows scientists to study the disease without infecting humans. Unfortunately, rhesus macaques are some of the largest and most expensive animals for these studies, but after research testing ferrets or hamsters as potential models, the primates are the best alternative.
Overall, rapid progress is being made to facilitate detection, surveillance and research on nCoV. The new serologic tests will make it easier to detect cases of nCoV. Since the new tests require less expensive equipment, it will also make it easier for more laboratories to offer the test, expanding the surveillance network to detect cases that may appear beyond the Middle East. The development of an animal model for the disease will help us understand how the virus can cause such severe symptoms, and will enable researchers to start testing potential vaccine candidates.
While the threat of an epidemic is still present, these new advances will help public health officials be more prepared.
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Article III (Check title later)
New Research on HIV Antibodies: Is a Vaccine in Sight?
【Time5】
Researchers are taking a new approach to combat HIV; rather than focus on the virus, scientists are now looking at patients for an answer. Specifically, researchers are looking at those who have successfully held HIV at bay. New research, published in Nature, may be key in the development of a vaccine for HIV.
HIV is the virus that causes AIDS, a disease that destroys the immune system. When a person is infected by any pathogen, the immune system starts producing antibodies, or proteins that identify and neutralize pathogens. For the first few weeks after infection, antibodies can fight off HIV, even as it mutates. However, the body cannot keep up with these mutations and eventually fails to produce enough antibodies to fight HIV.
The researchers, led by a team at the Duke University Human Vaccine Institute, were interested in a special type of antibody called broadly neutralizing antibodies (bNAbs). bNAbs are unlike regular antibodies because they can continually fight HIV even as it mutates. However, only about twenty percent of people produce this type of antibody as a response to infection with HIV.
The scientists collected blood samples over several years from a patient who was known to produce bNAbs. They studied how the virus evolved from soon after he was infected and how the patient’s body responded by producing bNAbs.
If scientists can understand what triggers the production of these powerful antibodies, they could theoretically create a vaccine that could also initiate production of bNAbs. A vaccinated person’s body would then have the antibodies needed to fight off HIV.
Future work will need to look at the immune response of other people who naturally produce bNAbs in addition to this one case. Dr. Barton Haynes, a leader of the research at Duke, explained to Time Magazine, “The hope is that by mapping individual pathways to generating broadly neutralizing antibodies, we can find some commonalities among people even though everyone is different.”
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【Rest】
Many successful vaccines have been developed to prevent other devastating viral infections, including measles and smallpox, for example. HIV, however, has some key differences that have made the development of a successful vaccine difficult for over thirty years. Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, cited HIV’s ability to hide from the immune system and mutate quickly as key reasons for this difficulty. Cost and the difficulty of clinical trials are also barriers to developing a vaccine.
This research is by no means the only work being done on a vaccine for HIV. The International AIDS Vaccine Initiative Report catalogues scientists’ work on an HIV vaccine around the world. The site includes a database of vaccines that are currently being or have been tested in clinical trials.
While this research is very promising, it presents many questions for future research to address. Dr. Louis Picker, an HIV vaccine specialist at Oregon Health and Science University cautioned that the findings are "a road map to vaccine development, yes -- but it's like one of those maps of the world from the year 1400.”
The research at Duke also focused on a single bNAb antibody called CH103. Researchers agree that a successful vaccine will need to trigger the production of more than one bNAb in order to produce a sufficient defense against HIV. William Schief, a protein engineer who specializes in vaccine design at the Scripps Research Institute pointed this out. “It poses the question for the vaccine-design field of how much of that viral diversity we need to incorporate into our vaccine regimens to try to elicit broadly neutralizing antibodies.”
Since HIV emerged in 1981, over 25 million people have died from the disease. In Sub-Saharan Africa, where the disease is most highly concentrated, one in twenty people are living with HIV. While the disease has no cure, antiretroviral drugs can effectively treat the infection.
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Part II Obstacle Article IV (Check title later)
The New Virus on the Block: H7N9 Case Counts, Explanations and Updates
The much-awaited springtime seems to have an unfortunate knack for bringing us scary diseases. Almost exactly ten years ago, surgical masks were à la mode, and the World Health Organization was reacting to the outbreak of what we now know as Severe Acute Respiratory Syndrome, or SARS. Four years ago this month, we were working hard to track and stop the spread of the 2009 H1N1 pandemic swine flu.
Today, the public health and medical worlds are faced with not one, but two emerging diseases: the novel coronavirus, and avian influenza H7N9 – a virus previously only seen in animals.
We are rapidly learning a lot about both of these viruses. Yet, there is one key fact that remains unknown: what is transmitting this virus to humans? What is the reservoir for this virus?
As previously reported, on March 31, three cases (including two deaths) of H7N9 were confirmed in Shanghai and Anhui Province, China. These marked the first documented cases of human H7N9.
Since March 31, the case count has steadily increased up to 16 cases including six deaths. The latest cases, a 61-year-old woman and a 79-year-old man from Nanjing, were reported this morning (EDT). Sixty-five contacts are now under surveillance – officials are looking for abnormal symptoms and evidence of human-to-human transmission.
As Canadian reporter Helen Branswell explains, through genetic sequencing of this virus, scientists know that all the genes are avian, but it’s a bird flu virus that knows how to adapt to mammals – specifically, humans. The WHO suggests not only that this virus can bind to human cells, but it can also grow at temperatures close to the human body temperature.
Yesterday, the Chinese Ministry of Agriculture revealed that strains of H7N9 that bore serious resemblance to the H7N9 infecting humans, were found in pigeons in Shanghai. In an encouraging sign of transparency, the Chinese government promptly reported the finding to the OIE (the world health organization for animals). As a result, Shanghai officials are ordering the slaughter of poultry.
Influenza infects and spreads in different animals. Birds, pigs, dogs, horses, and aquatic mammals (seals and whales) can all be infected and sick with the flu. Let’s review. There are three different types of influenza: A, B, and C. Influenza A can be broken down into subtypes differentiated by the proteins, hemagglutinin and neuraminidase, that are found on the virus. Some of these different subtypes are influenza A H1N1, H3N8, H3N2, H5N1, and the now famous H7N9. These subtypes can be broken down into different strains. For example, there are different strains of H1N1.
Different subtypes of the virus can infect and cause disease in different species. Birds, according to the WHO, provide a vast reservoir for influenza A viruses. One of the most concerning is H5N1. H5N1 historically only infected birds, but in 1997, there was an outbreak among humans in Hong Kong. The virus reemerged in people in 2003 and 2004. Since 2003, about 387 people have been infected with H5N1 and 245 have died. The good news is that this virus is not well adapted to humans, so human to human transmission is rare, at least for the moment. If there is no sustained human-to-human spread of H7N9, this virus could prove similar to H5N1. In the rare case when human-to-human transmission of H5N1 was suspected, it was typically in a small cluster. Clearly, we will have to continue careful monitoring of the spread of H7N9.
So why is it called ‘avian influenza’ or ‘swine flu,’ yet, people get sick? Welcome to Reassortment 101. When someone becomes sick with influenza, the influenza virus is actually latching on to the human host cells and hijacking their DNA to allow itself to replicate. Once the virus is replicated, it leaves the cell to infect other cells. Reassortment can occur when a host is infected with more than one influenza virus at a time, and some of the influenza virus RNA segments mix together. So, when the new influenza virus – that which has been produced inside the human host cell – is ready to bust out and infect other cells, it can be a combination of segments from two different influenza viruses.
The likelihood a host will be infected with two different influenza viruses depends on the host and the influenza viruses circulating. This is where pigs come in. Pigs are susceptible to infection from both avian and human influenza viruses, making them a playground for segment-swapping viruses. Both human and avian influenza viruses require the existence of very specific cells to bind to, if they are to cause infection. Mammals don't have the binding or “receptor” cells that birds do, and vice versa. However, pigs have both of these receptor cells in their respiratory tracts. Pigs can either serve as an intermediary host, transmitting influenza from one species to another, or they can serve as a “mixing vessel,” where influenza viruses reassort and new viruses (reassortants) emerge.
The bottom line is that we should take the flu far more seriously than we do. It is an immensely tricky virus that is prone to change and therefore a constant challenge to vaccine producers. We have seen influenza viruses change in the past and cause outbreaks both mild and quite serious (2009 H1N1 pandemic). H7N9 is typically a low pathogenic virus in birds, meaning that if it in infects birds, it causes a mild illness that is not very obvious. This makes it hard to know how common it is in China’s healthy appearing birds.
It seems to be more pathogenic in humans, but we can’t say for certain. As Branswell points out, flu illness follows a certain pattern in people: there are a few severe and fatal cases, and loads of sick people with mild illness that may not even know they have the flu. For the most part, people stick out the illness in bed, without giving it a second thought. So, we should remember that the cases we are counting now, do not necessarily represent the whole spread of this virus. There could be very mild cases not being diagnosed. If that is the case, maybe the virus is not as severe as it seems. Also, it could suggest that something different about how it spreads.
People infected with H7N9 are presenting with severe pneumonia. The WHO recommends that people wash their hands. All the time, and then again. No travel or trade restrictions have been issued for China.
There is currently no vaccine for H7N9, but experts are debating the development of one. Reuters reports that creating an H7N9 vaccine would be at the expense of seasonal flu shots. One of my professors famously stated that public health is “The art and science of deciding who dies, when, and with what degree of misery.” Public health policy decisions are based on maximizing the overall public health, but there is no way to protect everyone from everything. The seasonal flu may not be serious for most of those infected, but every year between 3,000 and 49,000 Americans die from the flu. Experts are working to learn more about the biology of the virus, and H7N9’s potential to cause a pandemic so that they can make fully informed decision on vaccine manufacturing
There is no specific treatment, either, but the WHO states that H7N9 is susceptible (vulnerable) to certain drugs such as oseltamivir and zanamivir. In the meantime, enhanced surveillance for unexplained pneumonias, epidemiological investigations of the contacts of cases and animal health investigations are being conducted.
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发表于 2013-4-15 15:41:35
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