Geneva:

Covid-19 is still killing around 1,700 people a week around the world, the World Health Organization said Thursday, as it urged at-risk populations to keep up with their vaccinations against the disease.

WHO director-general Tedros Adhanom Ghebreyesus sounded a warning on declining vaccine coverage.

Despite the continued death count, “data show that vaccine coverage has declined among health workers and people over 60, which are two of the most at-risk groups,” the UN health agency’s chief told a press conference.

“WHO recommends that people in the highest-risk groups receive a Covid-19 vaccine within 12 months of their last dose.”

More than seven million Covid deaths have been reported to the WHO, though the true count of the pandemic is thought to be far higher.

Covid-19 also shredded economies and crippled health systems.

Tedros declared an end to Covid-19 as an international public health emergency in May 2023, more than three years on from when the virus was first detected in Wuhan, China, in late 2019.

The WHO has urged governments to maintain virus surveillance and sequencing, and to ensure access to affordable and reliable tests, treatments and vaccines.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

A worker fumigating a private building surroundings to control mosquitoes and to prevent spread of dengue. File
| Photo Credit: K. Bhagya Prakash

Can the dengue virus beat the coronavirus and is it why the early wave of the pandemic in 2020 resulted in fewer COVID deaths or severe infections compared to Europe or North America where dengue is not endemic? Research from the CSIR-Indian Institute of Chemical Biology, Kolkata hints at these intriguing possibilities following an analysis of antibodies from people infected with dengue and testing them against a kind of coronavirus called murine hepatitis virus (mouse coronavirus). In research settings, this virus — being part of the same family of human coronaviruses — is considered a good surrogate to study the behaviour of the coronavirus strains that infected people during the pandemic.

Their results, published in the peer-reviewed Journal of Medical Virology this week, suggest that the antibodies following a dengue infection were able to ‘neutralise’ these coronavirus. For their analysis, the scientists relied on a combination of computer-modelling studies as well as cell-culture studies, the latter demonstrating how antibodies from dengue were able to engulf and bind the coronavirus proteins.

However, this protective effect did not necessarily expand to all coronavirus variants.

These latest studies build on the lab’s work from 2020 that blood tests specific to check for dengue sometimes led to a positive SARS-CoV-2 test.

“We experimentally demonstrated that serum samples from dengue patients have the potential to bind to and “mask” the surface of several coronaviruses, including SARS-CoV-2. We performed “virus neutralization” tests in cell cultures and showed that such “masking” by dengue antibodies can indeed, block coronavirus entry into susceptible cells,” Dr. Subhajit Biswas, Principal Scientist and the main author of the study, told The Hindu.

The dengue family of viruses are different from the coronavirus family and hence infection from one, in normal circumstances, is not expected to protect against the other. What is known about dengue is that there are four major serotypes, or strains, that cause dengue infections. Strains Denv-1 and Denv-2 are the most common in India. However, being infected with one does not protect against the other and, in fact, a re-infection involving a different strain can be more dangerous — a phenomenon called antibody-dependent enhancement (ADE) in dengue. Whether the prevalence of dengue in dengue-endemic countries of Southeast Asia may be triggering newer mutations in the coronavirus is a factor that needs to be investigated more extensively, the authors suggest in their study.

That the early stages of the pandemic saw a decline in dengue in India has been independently reported. The National Vector Borne Disease Control Programme of India reported a sharp decline of 75% (39,419 versus 1,57,315) in dengue incidence during 2020 as compared with 2019. “The possible reasons for this reduction could be lower transmission of the vector, less exposure due to COVID-19 lockdown, and, potentially, a disparity in the reported data possibly due to underdiagnosis or underreporting because of increased attention to the COVID-19 pandemic,” said a 2021 study in the American Journal of Tropical Medicine and Hygeine.

“In this paper, we provided several pieces of experimentally obtained evidence that pre-existing dengue immunity might have played some protective role in reducing the COVID severity and mortality in dengue-prone regions like Southeast Asia compared to regions where dengue does not occur frequently, like Europe and North America. Perhaps this is why, historically, human coronaviruses have been rarely encountered as a causative agent of “severe acute respiratory infections, SARI” from India, highly endemic for dengue virus,” he added.

The dilemma was whether the cross-reactive antibodies would provide partial protection against severe dengue infection or lead to increased severity due to the well-known phenomenon of antibody-dependent enhancement seen in dengue.  We hypothesize that the presence of antibodies to SARS-CoV-2 might decrease the severity of dengue. Larger multicentric clinical studies or population data from dengue endemic regions might help in understanding the existence of the cross-reactive, cross-protective association between these two single-stranded, positively coiled +SS RNA viruses.

“In 2020, deaths around the world rose by 10.8% compared to 2019, and in 2021, they rose by 7.5% relative to 2020.”
| Photo Credit: Reuters

COVID-19 (coronavirus) replaced stroke to become the second-leading cause of death globally in 2021, causing 94 deaths per one lakh population and slashing life expectancy by 1.6 years, an international research published in The Lancet journal has found.

“Disrupting more than three decades of consistent improvements in life expectancy and deaths, COVID-19 reversed this long-standing progress to emerge as “one of the most defining global health events of recent history,” researchers said.

“In 2020, deaths around the world rose by 10.8% compared to 2019, and in 2021, they rose by 7.5% relative to 2020. Death rates too followed a similar trend, rising by 8.1% in 2020 and an additional 5.2% in 2021,” the study estimated.

“Globally, COVID-19 and related deaths were responsible for slashing life expectancy by 1.6 years between 2019 and 2021, even as reduced deaths from infections, stroke, and of newborns, among others, had helped steadily enhance life expectancy between 1990 and 2019,” the researchers found.

“India lost 1.9 years of life expectancy due to COVID-19, resulting in a net gain of 7.9 years of life expectancy between 1990 and 2021,” the study showed. “COVID-19 had a pronounced influence on the reduction in global life expectancy that occurred,” the authors wrote.

The researchers forming the Global Burden of Disease (GBD) Causes of Death Collaborators estimated mortality and years of life lost from 288 causes of death across 204 countries and territories for every year from 1990 until 2021. Region-wise, death rates from COVID-19 were the highest in the sub-Saharan Africa.

“In Latin America and the Caribbean, it was at 271 per one lakh population and almost 200 deaths per one lakh population, respectively. The rate was the lowest in southeast Asia, east Asia, and Oceania at around 23 deaths per one lakh population,” the researchers estimated.

“The impact of COVID-19 on life expectancy was found to be wide-ranging in severity, with Andean Latin America seeing a loss of 4.9 years and the southern sub-Saharan Africa seeing a reduction of 3.4 years, to the east Asia, which witnessed almost no change,” they said in the study.

“The leading cause of death worldwide in 2021 continues to be ischaemic heart disease, as was the case in 2019 and 1990,” the researchers found. The disease is caused by a reduced blood flow to a certain body part due to clotting or constricting blood vessels.

Stroke, at the third position amongst the top five causes of death, was found to be followed by chronic obstructive pulmonary disease (COPD) at fourth, and other pandemic-related mortality at fifth. COPD is a lung condition usually seen to affect heavy smokers.

The GBD study, providing “latest comprehensive estimates of cause-specific mortality,” gives insights about the global landscape of disease before and during the first two years of the pandemic, revealing changes in disease-burden patterns that followed, according to the researchers, coordinated by the Institute for Health Metrics and Evaluation (IHME), University of Washington, U.S.

File photo used for representational purpose only.

Children infected with the Omicron variant remain infectious for three days on average after testing positive for the SARS-CoV-2 virus, according to a study.

Researchers at the University of Southern California (USC) and Stanford University in the U.S. noted that school policies that require students with COVID-19 to stay out of the classroom for five days are more than sufficient.

“We are basically saying five days is more than sufficient; public health and education leaders may consider shorter durations,” said study co-author Neeraj Sood, Director of the COVID-19 Initiative and a senior fellow at the USC Schaeffer Center.

The study, published in the journal JAMA Pediatrics, found that the median time of infectivity was three days, with 18.4% and 3.9% of children still infectious on day five and day 10, respectively.

The researchers also found no association between how long children were infectious and whether they were vaccinated, suggesting return-to-school policies may not need discriminate by vaccine or booster status.

The study seeks to inform policymakers who grapple with how long children must isolate when they contract COVID-19. Such self-isolation policies, aimed at halting the spread of the virus, can negatively interrupt children’s education.

“We want to protect other children in the school who could potentially get infected, but at the same time, we don’t want to disrupt education for the child who is infected, given the amount of disruption that’s already happened,” said Mr. Sood.

“The duration of infectivity is an important parametre into figuring out what the optimal duration of self-isolation should be,” he added.

The researchers partnered with a virus testing company and examined nasal swabs from 76 children in Los Angeles County who were between the ages of seven and 18 and tested positive for COVID-19.

Survey participants provided samples during five home visits over a 10-day period and samples were examined in a lab to find evidence of cell death, a sign of infectivity. All participants were infected with the Omicron variant of COVID-19.

“We wanted to capture how infectivity changed over the 10-day window,” said study lead author Nikhilesh Kumar, a Doctor of Medicine student at the USC Keck School of Medicine.

The findings are consistent with previous research on adults who contracted the Omicron variant, which showed no association between vaccination status and time of infectivity.

“That research, published in the New England Journal of Medicine, showed adults with Omicron were infected for a slightly longer duration, with a median time of five days,” the authors noted.

The team called for further research so that policymakers can consider adjusting the time students must stay out of the classroom.

Many tiny organisms including bacteria, fungi and viruses normally live on our bodies, and even inside us. These are called the microbiome. The large number of these organisms living in the gastrointestinal tract are collectively known as the gut microbiome.

Increasingly the gut microbiome is recognised as playing a large part in health and disease, particularly relating to human physiology, metabolism and immune function.

There are now more than 700 published papers looking at the interaction between COVID and the gut microbiome. Many of these studies demonstrate the possible contribution of gut bacteria to COVID infection and severity, as well as the effect COVID (and its treatment) potentially has on our gut bacteria.

Now, a new study has found severe COVID may be related to fungal bugs in our gut microbiome. This could be through a variety of changes to the immune system in response to specific fungal species.

Also Read | Humans evolved with their microbiomes – like genes, your gut microbes pass from one generation to the next

What the study did

Fungal organisms in the microbiome are referred to as the fungal microbiota, or mycobiota. While it’s normal to have a range of fungal organisms in the gut, changes in the types or amount can be linked to disease, just like with variations in gut bacteria.

In the study published in Nature Immunology, the researchers investigated the possible relationship between mycobiota and COVID in a few different ways.

First, they compared patients with and without COVID, looking at the levels of certain fungal organisms in samples from their gastrointestinal tracts. This included 66 people with severe COVID, 25 with moderate COVID and 36 without COVID.

The researchers also measured antibodies in the participants’ blood against these same organisms, which lets us know that they triggered an immune response.

Explained | How does the gut microbiome link to autism spectrum disorders?

To investigate further, the researchers conducted experiments in mice. They gave the mice some of the fungal organisms taken from COVID patients and measured some of the same outcomes, including antibodies in the blood. They also looked to see if certain treatments, such as antifungals, would make a difference.

While this isn’t the first study looking at gut mycobiota and COVID, it’s very comprehensive and reports some interesting findings.

What the study found

The researchers detected a greater amount of fungal organisms in patients who had COVID compared with controls who did not.

Antibodies to certain fungi were also heightened in the blood of COVID patients. In other words, the presence of these fungal organisms and an associated immune response seems to be linked to a more severe COVID infection. In particular, two Candida species and S. cerevisiae were linked to disease severity.

When the researchers isolated live fungi from fecal samples of COVID patients, Candida albicans was common in the gut of patients with COVID, and its growth correlated with more severe disease.

Also Read | COVID and your gut: How a healthy microbiome can reduce the severity of infection – and vice versa

To look at the impact of these fungal species on immune responses, mice were colonised with Candida strains isolated from the COVID patients.

The researchers found older mice who were colonised with C. albicans and then infected with COVID showed a very different immune response compared to mice that weren’t given the Candida fungus. This included having more immune cells called neutrophils in the blood and increases in other markers of inflammation including in the lungs.

Some of these changes were partially resolved with anti-fungal treatment or other specific anti-inflammatory medications that have shown benefit in COVID patients.

Some limitations

All of this suggests variations in the mycobiota may contribute to the excessive inflammatory immune response seen in severe cases of COVID. A link between the fungal microbiome and inflammation isn’t completely new – other studies have shown an impact on inflammatory conditions linked to similar changes in the mycobiota.

As with all studies, there are some limitations to consider here. First, the number of human participants was relatively low, with only 91 patients with COVID included, and 36 in the control group. Many parts of the study analysed even smaller groups of patients or patient samples.

Also Read | Are you sure you contain 10x as many microbes as human cells? 

Second, the study was conducted in 2020 during the first wave of COVID infections. A lot has changed since then including the virus itself. And most people have now not only been vaccinated but also previously exposed to the virus.

Nonetheless, this study raises many possibilities including perhaps being able to look at who might be a greater risk of more severe COVID based on their mycobiota. There may even be a possibility of trying to change the mycobiota to reduce the risks from COVID infection. But to get to these points we need a lot more research.

There are multiple factors that determine the make-up of our microbiome, including mycobiota. These are likely to include diet and lifestyle factors alongside other factors like medical conditions and treatments, such as antibiotics.

At this stage there are fewer proposed interventions for influencing mycobiota than for gut bacteria. But studies such as this one demonstrating the importance of the fungal bugs in our gut will hopefully lead to more research in the area.