herd immunity Archives - Amazing Health Advances

Will COVID-19 Become a Seasonal Virus?

AHA Publisher — Wed, 07 Oct 2020 07:00:15 +0000

Interview conducted by Emily Henderson, B.Sc. via News-Medical Net – In this News-Medical interview, Dr. Hadi Yassine and Dr. Hassan Zaraket speak about their research efforts during the COVID-19 pandemic, and their research into whether COVID-19 will become a seasonal virus. What provoked your research into the current COVID-19 pandemic? The question of whether COVID-19 will become seasonal and just wane in summer has been of interest since the beginning of the pandemic. Therefore, we decided to review the current knowledge on seasonality of respiratory viruses including common cold coronaviruses as well as drivers of seasonality and build on that evidence to project whether COVID-19 will follow suit of other seasonal respiratory viruses. Can you describe what is meant by a ‘seasonal virus’ and what are the common seasonal patterns observed? Seasonal viruses are those viruses that tend to circulate and peak during specific seasons (months) in the year. Respiratory viruses such as influenza, respiratory syncytial viruses, and common cold coronaviruses are known to spread and peak during cold months in countries with a temperate climate. Why do respiratory viruses follow seasonal patterns in temperate regions but not in tropical regions? This is not fully understood. Many factors affect seasonality including host susceptibility and behavior, and virus stability. Although respiratory viruses tend to circulate year-around in tropical regions, the peak activity is usually associated with the rainy season. Research has shown that for instance for influenza viruses low and high humidity promotes viral transmission, while moderate humidity does not promote transmissibility. It is worth noting here that transmission could be either by direct contact with infected persons/contaminated objects or airborne. These modes of transmissions are determined by temperature and humidity. For example, higher relative humidity will result in the formation of a large viral particle, which settles down on surfaces much faster, and hence, transmission occurs mostly through direct contact of contaminated surfaces. This could be one reason for the different seasonal patterns of respiratory viruses observed in tropical and temperate regions. How did you carry out your research into SARS-CoV-2 potentially becoming a seasonal virus? What did your results show? We reviewed existing knowledge on the seasonality of respiratory viruses and the current knowledge about SARS-CoV-2. We hypothesized that COVID-19 will continue to circulate year-round until herd immunity is achieved. In your research you stated that COVID-19 could become a seasonal virus but only when herd immunity is reached. Why is this? As population immunity builds up, the transmission rate of the virus will drop making it more susceptible to environmental factors that govern seasonality. How could herd immunity be reached for SARS-CoV-2? Ideally, vaccination and natural infections and cross-immunity with common cold coronaviruses can also contribute to reaching herd immunity. Why is it so critical that public health measures are introduced to help control the virus? The majority of populations are still susceptible to the infection. With the absence of effective vaccines and antivirals drugs, public health measures remain the only way to mitigate the pandemic. We have seen a tremendous rise in cases in many countries after the ease of restrictions. Do you believe that if strong public health measures are introduced, we could potentially manage the virus and prevent it from becoming a seasonal respiratory virus? It is difficult to say. Public health measures reduce COVID-19 transmission anyway, so it will be difficult to tell whether the reduction in virus activity is affected also by seasonal factors. Since 2000, four new coronaviruses appeared in the human population: one was controlled in about two years (SARS-Cov-1; 2002-2004), two became seasonal (HKU1 and NL63; 2005-ongoing), and one still causing sporadic cases, mostly in the Gulf States (MERS-CoV; 2012-ongoing). On the other hand, we experienced rapid and worldwide spread of SARS-CoV-2. We expect the virus to continue to spread until herd immunity is achieved and mostly become seasonal like HKU1 and NL63. On a related subject, FLU viruses have shown diminished circulation in most countries, even after the start of the fall season. This could be partially attributed to the social measures being applied (no big gathering, no schools, etc) in the community that have some level of immunity to the virus. What are the next steps in your research into COVID-19 and viruses? We will be monitoring respiratory viral infection including COVID-19 to determine any potential interferences among them. We will also monitor changes in the SARS-CoV-2 that might lead to evading the immune response. Where can readers find more information? https://www.frontiersin.org/articles/10.3389/fpubh.2020.567184/full About Dr. Hadi Yassine Dr. Yassine is an associate professor of infectious diseases and the section head of research at the Qatar University ‎Biomedical Research Center‎. He obtained his Ph.D. from the Ohio State University in 2009 and worked for five years at the Vaccine Research Center of NIH before he joined Qatar University in 2015. He published more than 70 articles and contributed to several patents on viral vaccines. About Dr. Hassan Zaraket Dr. Zaraket is an assistant professor of virology and assistant laboratory director of the Center for Infectious Diseases Research at the Faculty of Medicine, American University of Beirut (AUB). He has 14 years’ experience working on respiratory viruses including influenza. Before joining AUB, he worked at the Center of Excellence for Influenza Research and Surveillance at St Jude Children’s Research Hospital, USA. His work included studying emerging influenza viruses with pandemic potential such as H5N1 and H7N9.

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Immunity of Recovered COVID-19 Patients Could Cut Risk of Expanding Economic Activity

AHA Publisher — Sat, 09 May 2020 07:00:42 +0000

Georgia Institute of Technology via Newswise – While attention remains focused on the number of COVID-19 deaths and new cases, a separate statistic – the number of recovered patients – may be equally important to the goal of minimizing the pandemic’s infection rate as shelter-in-place orders are lifted. The presumed immunity of those who have recovered from the infection could allow them to safely substitute for susceptible people in certain high-contact occupations such as healthcare. Dubbed “shield immunity,” the anticipated protection against short-term reinfection could allow recovered patients to expand their interactions with infected and susceptible people, potentially reducing overall transmission rates when interactions are permitted to expand. New modeling of the virus’ behavior suggests that an intervention strategy based on shield immunity could reduce the risk of allowing the higher levels of human interaction needed to support expanded economic activity. The number of Americans infected by the novel coronavirus is likely much higher than what has been officially reported, and that could be good news for efforts to utilize their presumed immunity to protect the larger community. Serological Tests However, there are two important caveats to the strategy. The first is that the duration of immunity to reinfection by SARS-CoV-2 remains unknown; however, individuals who survived infections by related viral infections, like SARS, had persistent antibodies for approximately two years – and those who survived infection to MERS had evidence of immunity for approximately three years. The second issue is that determining on a broad scale who has antibodies that may protect them from the coronavirus will require a level of reliable serological testing not yet available in the United States. “Our model describes ways in which serological tests used to identify individuals who have been infected by and recovered from COVID-19 could help both reduce future transmission and foster increased economic engagement,” said Joshua Weitz, professor in the School of Biological Sciences and founding director of the Interdisciplinary Ph.D. in Quantitative Biosciences at the Georgia Institute of Technology. “The idea is to think in advance about how identifying recovered individuals could help serve the collective good, using information collected on neutralizing antibodies in new ways.” A paper describing the modeling behind the concept of shield immunity was published May 7 in the journal Nature Medicine by a team of researchers from Georgia Tech, Princeton University and McMaster University. The researchers studied the potential impacts of presumed immunity among recovered persons using a computational model of COVID-19 epidemiological dynamics, building upon a SEIR (susceptible-exposed-infectious-recovered) framework. In a population of 10 million citizens, for example, the model predicts that in a worst-case transmission scenario, implementation of an intermediate shielding strategy could help reduce deaths from 71,000 to 58,000, while an enhanced shielding plan could cut deaths from 71,000 to 20,000. The model also suggests that shielding could enhance the effects of social distancing strategies that may remain in place once higher levels of economic activity resume. Identification of individuals who have protective antibodies against the novel coronavirus has begun only recently. Antibody tests are not 100% specific, implying that tests can lead to false positives. However, targeted use of antibody testing in groups with elevated exposure will lead to increases in positive predictive value, even with imperfect tests. The serological antibody test differs from widespread polymerase chain reaction (PCR) testing being done to determine whether people are actively infected with the virus. Identifying Recovered Individuals Among healthcare professionals, serological testing could identify recovered individuals who might then be able to interact with patients with reduced concern for infection. Other recovered individuals could be used to help reduce transmission risk in nursing homes, the food service industry, emergency medical services, grocery stores, retailing and other essential operations. Across society, the relatively small number of individuals with immunity could substitute for people whose immunity status isn’t known; reducing transmission risk both for recovered individuals and those who remain immunologically naive. “We want to think about serology as an intervention,” Weitz said. “Finding out who is immune to the coronavirus could make a big difference in trying to reduce the risk to people who would be vulnerable by interacting with someone who could pass on the disease.” Serological testing to identify those with immunity might begin with healthcare workers, who may be more likely to have been infected by the coronavirus because of their exposure to infected persons, Weitz said. Because so many infections do not produce the distinctive COVID-19 symptoms, it’s likely that many people have recovered from the illness without knowing they’ve had had it, potentially expanding the pool of recovered persons. “There may be a deeper pool of individuals who can help within their own fields and other fields of specialization to reduce transmission,” Weitz said. “The reality is that people within high-contact jobs probably are likely to have a higher incidence of infection than other groups.” But using antibody information about individuals would create potential privacy issues, and require that those individuals make informed decisions about accepting additional risks for the greater good of the community. “What this model says is that if we could identify individuals who are immune, there is a chance that some individuals would not have to reduce their level of interaction with others because that interaction would be less risky,” he added. “Rather than trying to keep reducing interactions, which is helpful for reducing transmission but bad for what it does for the economy, we might be able to maintain interactions while reducing the risk, combined with other mitigation approaches.” Ultimately, addressing the pandemic will require development and mass production of a vaccine that could boost immunity levels beyond 60 percent in the general population. Until that is available, Weitz believes that shield immunity could become part of the approach to the challenge. “We don’t have a silver bullet,” he said. “Until we have a vaccine, we will have to use a combination of strategies to control COVID-19, and shield immunity is potentially one of them.” To read the original article click here.

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Sweden May Reach ‘Herd Immunity’ in Weeks as the Country Resists Total Lockdown

AHA Publisher — Sat, 25 Apr 2020 07:00:05 +0000

Angela Betsaida B. Laguipo, BSN via News-Medical Net – Herd immunity is a form of indirect protection against infectious diseases where a population develops sufficient immunity to a disease that that infection cannot spread within the group. A population can reach herd immunity if a large proportion has been exposed to the virus. Now, Sweden resisted total lockdown measures, unlike its neighboring countries, while experts believe herd immunity will be achieved in Stockholm within weeks. Europe has been badly hurt by the coronavirus disease (COVID-19). Several countries in Europe report a high number of confirmed cases, including Spain, Italy, France, Germany, and the United Kingdom. These countries have imposed lockdown measures, social distancing behaviors, and travel bans, in the attempt to contain the spread of the virus that causes COVID-19, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). “In major parts of Sweden, around Stockholm, we have reached a plateau (in new cases), and we already see the effect of herd immunity, and in a few weeks, we’ll see even more of the effects of that. And in the rest of the country, the situation is stable,” Dr. Anders Tegnell, chief epidemiologist at Sweden’s Public Health Agency, said in a statement. Voluntary Measures The country’s top epidemiologist says that Stockholm could attain herd immunity in weeks amid the country’s low-level lockdown measures. The measures are voluntary, and the government has faith in the residents that they will avoid social contact, while the country’s borders have remained open. Herd immunity is reached when approximately 60 percent of the population becomes immune to a virus. However, without a vaccine, scientists are analyzing if exposure and recovery from the COVID-19 will provide long-term immunity. In some countries such as Japan, China, and South Korea, reinfections of SARS-CoV-2 have been reported. “Each country has to reach ‘herd immunity’ in one way or another, and we are going to reach it in a different way,” Dr. Tegnell added. There are enough signals to show that we can think about herd immunity, about recurrence. Very few cases of reinfection have been reported globally so far. How long the herd immunity will last, we do not know, but there is definitely an immune response. As of writing, the country has reached an infection toll of 16,755 and a death toll of 2,021, which is a fatality rate of 12 percent, higher than the rates in other countries. Dr. Tegnell also said that the mortality rate in the country is high because the virus was introduced to nursing homes, endangering the lives of older adults. The sudden spike in novel coronavirus cases in Stockholm has raised questions about the country’s decision to combat the pandemic without resorting to lockdowns, which have left most of the countries in Europe in a standstill. Most countries have closed schools and have taken authoritarian measures to impose social distancing, implement curfews, band meeting of more than two people in public, and limit exposure to potential carriers. Sweden did something different. Rather than imposing strict social distancing measures and policies, the country aimed to keep public life as open as possible. People are still allowed to go to restaurants, send their children to school, and get a haircut, even if the cases have been rapidly increasing and the number of deaths has mounted. Stockholm alone accounts for more than half the fatalities. Little Restrictions Sweden’s foreign minister, Ann Linde, explains that the country’s approach is not similar to other countries. The government has not imposed a lockdown, and it relies on the people taking responsibility themselves. The coronavirus measures the country has rolled out include bars, restaurants, and malls remain open, and school classes are not suspended. The government has encouraged everyone against nonessential travels, while those who are 70 years old and above to stay at home. The only restrictions are that crowds of more than 50 people are banned, restaurants and bars are to serve only those who are seated, and people are barred from visiting nursing homes. Regardless of lenient lockdown measures, the country has ramped up its testing capacities, Sweden initially tested those who report symptoms or those who came to the hospital. Increasing testing capacities is the key to help the health system cope with the number of admissions. This way, the country can flatten the curve and prevent overwhelming the health system. The country is testing around 20,000 people each week but plans to increase that to about 100,000 in a few weeks. To read the original article click here.

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