H5N1

COVID-19 Epidemiological Update - 29 September 2023

WHO has published COVID-19 Epidemiological Update - 29 September 2023. Click or tap through to download the full report. The overview:

Globally, the number of new cases decreased by 55% during the 28-day period of 28 August to 24 September 2023 as compared to the previous 28-day period, with over 685 000 new cases reported. The number of new deaths decreased by 34% as compared to the previous 28-day period, with over 1900 new fatalities reported. As of 24 September 2023, over 770 million confirmed cases and over 6 million deaths have been reported globally. 

 In this edition, we include:  

• The COVID-19 epidemiological update at the global and the regional levels.  

• An update on hospitalizations and ICU admissions.  

• An update on the SARS-CoV-2 variants of interest (VOI) and variants under monitoring (VUM).

WHO: Weekly epidemiological update on COVID-19 - 3 August 2023

WHO has published Weekly epidemiological update on COVID-19 - 3 August 2023. Click or tap through to download the complete report. The overview:

Globally, over one million new COVID-19 cases and over 3100 deaths were reported in the last 28 days (3 to 30 July 2023). While five WHO regions have reported decreases in the number of both cases and deaths, the Western Pacific Region has reported an increase in the number of cases and a decrease in the number of deaths. 

As of 30 July 2023, over 768 million confirmed cases and over 6.9 million deaths have been reported globally. Currently, reported cases do not accurately represent infection rates due to the reduction in testing and reporting globally. 

During this 28-day period, 46% (107 of 234) of countries and territories reported at least one case to WHO – a proportion that has been declining since mid-2022. 

In this edition, we include:  

• The COVID-19 epidemiological update at the global and the regional levels  

• An update on hospitalizations and ICU admissions  

• An update on the SARS-CoV-2 variants of interest (VOI) and variants under monitoring (VUM)  

• An update on the vaccine effectiveness of primary series and booster vaccination against the Omicron and its descendant lineages

The evolution of SARS-CoV-2 seroprevalence in Canada: A time-series study, 2020–2023

Via CMAJ: The evolution of SARS-CoV-2 seroprevalence in Canada: a time-series study, 2020–2023. The abstract:

Background: During the first year of the COVID-19 pandemic, the proportion of reported cases of COVID-19 among Canadians was under 6%. Although high vaccine coverage was achieved in Canada by fall 2021, the Omicron variant caused unprecedented numbers of infections, overwhelming testing capacity and making it difficult to quantify the trajectory of population immunity.  

Methods: Using a time-series approach and data from more than 900 000 samples collected by 7 research studies collaborating with the COVID-19 Immunity Task Force (CITF), we estimated trends in SARS-CoV-2 seroprevalence owing to infection and vaccination for the Canadian population over 3 intervals: prevaccination (March to November 2020), vaccine roll-out (December 2020 to November 2021), and the arrival of the Omicron variant (December 2021 to March 2023). We also estimated seroprevalence by geographical region and age.  

Results: By November 2021, 9.0% (95% credible interval [CrI] 7.3%–11%) of people in Canada had humoral immunity to SARS-CoV-2 from an infection. Seroprevalence increased rapidly after the arrival of the Omicron variant — by Mar. 15, 2023, 76% (95% CrI 74%–79%) of the population had detectable antibodies from infections. The rapid rise in infection-induced antibodies occurred across Canada and was most pronounced in younger age groups and in the Western provinces: Manitoba, Saskatchewan, Alberta and British Columbia.  

Interpretation: Data up to March 2023 indicate that most people in Canada had acquired antibodies against SARS-CoV-2 through natural infection and vaccination. However, given variations in population seropositivity by age and geography, the potential for waning antibody levels, and new variants that may escape immunity, public health policy and clinical decisions should be tailored to local patterns of population immunity.

WHO: Weekly epidemiological update on COVID-19 - 3 August 2023

WHO has published Weekly epidemiological update on COVID-19 - 3 August 2023. Click or tap through to download the full report. The overview:

Globally, over one million new COVID-19 cases and over 3100 deaths were reported in the last 28 days (3 to 30 July 2023). While five WHO regions have reported decreases in the number of both cases and deaths, the Western Pacific Region has reported an increase in the number of cases and a decrease in the number of deaths. 

As of 30 July 2023, over 768 million confirmed cases and over 6.9 million deaths have been reported globally. Currently, reported cases do not accurately represent infection rates due to the reduction in testing and reporting globally. 

During this 28-day period, 46% (107 of 234) of countries and territories reported at least one case to WHO – a proportion that has been declining since mid-2022. 

In this edition, we include:  

• The COVID-19 epidemiological update at the global and the regional levels  

• An update on hospitalizations and ICU admissions  

• An update on the SARS-CoV-2 variants of interest (VOI) and variants under monitoring (VUM)   

• An update on the vaccine effectiveness of primary series and booster vaccination against the Omicron and its descendant lineages

UK almost ‘flying blind’ on Covid this autumn, experts say

Via The Guardian: UK almost ‘flying blind’ on Covid this autumn, experts say. Excerpt:

The UK is nearly “flying blind” when it comes to Covid this autumn, experts have said, amid an increase in cases.  

While the UK Health Security Agency (UKHSA) continues to track some metrics of Covid, including hospitalisation numbers, many of the community surveillance studies tracking infection levels have finished.  

Now experts have said the situation is leaving the country in the dark about how Covid may play out in the months ahead.  

Christina Pagel, a professor of operational research at University College London, said a new wave of Covid appeared to be under way – possibly driven by waning immunity, new variants of Omicron, and factors including poor weather keeping people inside.  

With the autumn coming on and people returning to school and work, Covid pressures may increase, Pagel added.  

“We might see the wave continue to grow, and grow faster, in September,” she said.  

As well as public health measures including reintroducing high-quality masks within healthcare settings, Pagel said she would support bringing back the nationwide infection survey published by the Office for National Statistics for autumn and winter, as well as expanding it to cover flu and RSV.  

Failing that, she said, wastewater monitoring should be reinstated across the UK as a cheaper alternative that is used in many countries to track Covid prevalence and variants. Such schemes have recently been cut in England and Wales.  

“What worries me most is if we get a repeat of the last winter NHS crisis this winter again, with Covid, flu and RSV all hitting around the same time,” said Pagel. “We are definitely flying near blind.”  

Prof Rowland Kao, an epidemiologist at the University of Edinburgh, also highlighted the decline in surveillance.  

“With seasonal flu, we have of course a certain amount of predictability with the many years of data. However, with Covid, now that we don’t have those multiple data streams to rely on, it’s harder to say what is happening [in the general population],” he said.  

Kao added that the variant emergence patterns for Covid were largely unknown and Covid was not simply following seasonal patterns.

Outcomes and characteristics of patients hospitalized for COVID-19 in British Columbia, Ontario and Quebec during the Omicron wave

Thanks to FluTrackers for alerting me to this report in CMAJ Open: Outcomes and characteristics of patients hospitalized for COVID-19 in British Columbia, Ontario and Quebec during the Omicron wave. The abstract:

Background: Omicron is the current predominant variant of concern of SARS-CoV-2. We hypothesized that vaccination alters outcomes of patients hospitalized with COVID-19 during the Omicron wave and that these patients have different characteristics and outcomes than in previous waves. 

Methods: This is a substudy of the Host Response Mediators in Coronavirus (COVID-19) Infection (ARBs CORONA I) trial, which included adults admitted to hospital with acute COVID-19 up to July 2022 from 9 hospitals in British Columbia, Ontario and Quebec. We excluded emergency department visits without hospital admission, readmissions and admissions for another reason. Using adjusted regression analysis, we compared mortality and organ dysfunction between vaccinated (≥ 2 doses) and unvaccinated patients during the Omicron wave, as well as between all patients in the Omicron and first 3 waves of the COVID-19 pandemic.  

Results: During the Omicron wave, 28-day mortality was significantly lower in vaccinated (n = 19/237) than unvaccinated hospitalized patients (n = 12/127) (adjusted odds ratio [OR] 0.36, 95% confidence interval [CI] 0.15–0.89); vaccinated patients had lower risk of admission to the intensive care unit, invasive ventilation and acute respiratory distress syndrome and shorter hospital length of stay. Patients hospitalized during the Omicron wave had more comorbidities than in previous waves, and lower 28-day mortality than in waves 1 and 2 (adjusted OR 0.38, 95% CI 0.24–0.59; and 0.42, 95% CI 0.26–0.65) but not wave 3 (adjusted OR 0.81, 95% CI 0.43–1.51) and had less organ dysfunction than in the first 2 waves.  

Interpretation: Patients who were at least double vaccinated had lower mortality than unvaccinated patients hospitalized during the Omicron wave. Patients hospitalized during the Omicron wave had more chronic disease and lower mortality than in the first 2 waves, but not wave 3. Changes in vaccination, treatments and predominant SARS-CoV-2 variant may have decreased mortality in patients hospitalized during the Omicron wave.

WHO: Weekly epidemiological update on COVID-19 - 27 July 2023

WHO has published Weekly epidemiological update on COVID-19 - 27 July 2023. The overview:

Globally, over 868 000 new COVID-19 cases and over 3700 deaths were reported in the last 28 days (26 June to 23 July 2023). While five WHO regions have reported decreases in the number of both cases and deaths, the Western Pacific Region has reported an increase in the number of both cases and deaths.  

As of 23 July 2023, over 768 million confirmed cases and over 6.9 million deaths have been reported globally. Currently, reported cases do not accurately represent infection rates due to the reduction in testing and reporting globally. During this 28-day period, 52% (122 of 234) of countries and territories reported at least one case – a proportion that has been declining since mid-2022.    

In this edition, we include:  

• The COVID-19 epidemiological update at the global and the regional levels  

• An update on hospitalizations and ICU admissions  

• An update on the SARS-CoV-2 variants of interest (VOI) and variants under monitoring (VUM)

Swift and extensive Omicron outbreak in China after sudden exit from ‘zero-COVID’ policy

Via Nature Communications, a shocking report: Swift and extensive Omicron outbreak in China after sudden exit from ‘zero-COVID’ policy. The abstract, with my bolding, and then a comment:

In late 2022, China transitioned from a strict ‘zero-COVID’ policy to rapidly abandoning nearly all interventions and data reporting. This raised great concern about the presumably-rapid but unreported spread of the SARS-CoV-2 Omicron variant in a very large population of very low pre-existing immunity. 

By modeling a combination of case count and survey data, we show that Omicron spread extremely rapidly, at a rate of 0.42/day (95% credibility interval: [0.35, 0.51]/day), translating to an epidemic doubling time of 1.6 days ([1.6, 2.0] days) after the full exit from zero-COVID on Dec. 7, 2022. Consequently, we estimate that the vast majority of the population (97% [95%, 99%], sensitivity analysis lower limit of 90%) was infected during December, with the nation-wide epidemic peaking on Dec. 23. 

Overall, our results highlight the extremely high transmissibility of the variant and the importance of proper design of intervention exit strategies to avoid large infection waves.

In the discussion section of the report, the authors write:

With an infection fatality ratio between 0.1 and 0.2% for the Omicron variant, we would expect between 1.3 and 2.6 million COVID-19 deaths in China during Dec. 2022 as well as Jan. 2023 (because of the delay from infection to death).

And that is with a case fatality rate of 0.1-0.2 percent. So 1.37 billion people in China contracted the Omicron strain of SARS-CoV-2 in December 2022, and at least one or two in a thousand died of it. The government saw it coming because Omicron was already spreading, and dropped most "lockdown" measures. It was a calculated risk: one or two million dead in a little over a month, millions more needing hospitalization, and the country survived the blow.

China’s rolling COVID waves could hit every six months — infecting millions

Via Nature: China’s rolling COVID waves could hit every six months — infecting millions. Excerpt:

The latest surge in COVID-19 cases in China is not surprising to researchers, who say that China will see an infection cycle every six months now that all COVID-19 restrictions have been removed and highly infectious variants are dominant. But they caution that rolling waves of infection carry the risk of new variants emerging.  

“Unfortunately, a new reality with this virus [is that] we will have repeated infections,” says Ali Mokdad, an epidemiologist at the Institute for Health Metrics and Evaluation at the University of Washington in Seattle. “The fear is that this virus will produce a new variant that can compete with the current ones and is more severe.”  

The current surge is caused mainly by a highly infectious subvariant of Omicron called XBB.1.5, first identified in India last August. According to Nanshan Zhong, a prominent respiratory physician in China, as many as 65 million people could become infected per week by the end of June.  

This is the first major reinfection wave that China has seen since the central government dropped all its COVID-19 control measures in December, prompting a widespread Omicron outbreak.  

China has vaccinated more than 90% of its population, and the outbreak in December infected at least 85% of its people, says Zhong. But immunity is waning, and XBB can evade protection from vaccines and prior infections. Mokdad says that, although XBB has not caused a major rise in hospitalizations and deaths, the sheer number of infections could put pressure on China’s health-care system.  

XBB is also causing minor waves in other parts of the world, such as Singapore and the United States.  

“This is what we see everywhere, but with a large population such as China, it is more apparent,” says Mokdad.  

Yunlong Cao, an immunologist at Peking University in Beijing, and his team have found that antibodies generated against Omicron variants BA.5 and BF.7, the dominant strains during the December wave in China, can provide about four months of protection against strains such as XBB.  

Kayoko Shioda, an epidemiologist at Boston University in Massachusetts, says that previous COVID-19 surges in other countries have shown that XBB is more transmissible than earlier forms. “Once it enters the population, XBB spreads and becomes the predominant variant much quicker than other variants,” she says.  

Last December, more than 200 million people in China contracted COVID-19 in 20 days. This time, the wave is spanning several months, owing to the differences in people’s immune backgrounds, such as antibody levels, says Cao.  

“The peak of COVID-19 waves will generally become flatter and more stretched out after each cycle, which is a pattern we see in countries like the US. People are still getting infected in the US, just not all at once,” he adds. A flatter wave would also lessen the burden on health-care systems, Cao says.

COVID's future: Mini-waves rather than seasonal surges

Via Nature: COVID's future: mini-waves rather than seasonal surges. Excerpt:

Whether you call it a surge, a spike, a wave or perhaps just a wavelet, there are signs of a rise in SARS-CoV-2 infections — again. A growing proportion of tests in some countries are coming back positive, and new variants, most notably a lineage called XBB.1.16, are pushing aside older strains, fuelling some of the uptick in cases.  

Welcome to the new normal: the ‘wavelet’ era. Scientists say that explosive, hospital-filling COVID-19 waves are unlikely to return. Instead, countries are starting to see frequent, less deadly waves, characterized by relatively high levels of mostly mild infections and sparked by the relentless churn of new variants.

Wavelets don’t always create a dramatic spike in hospitalizations and deaths; their effects on health vary between countries. But the relentless series of wavelets looks very different from the slower, annual circulation patterns of influenza and cold-causing coronaviruses, and it seems increasingly unlikely that SARS-CoV-2 will settle into a flu-like rhythm anytime soon, say scientists.  

“We haven’t slowed down in the last year, and I don’t see what factors would cause it do so at this point,” says Trevor Bedford, an evolutionary biologist at the Fred Hutchinson Cancer Center in Seattle, Washington. “It will be a continually circulating respiratory disease. It may be less seasonal than things we’re used to.”  

Victorious variant  

In March, scientists in India started seeing signs that a new SARS-CoV-2 variant was causing a rise in infections. The XBB.1.16 lineage has displaced others that drove case surges in India several months ago, says Rajesh Karyakarte, a microbiologist at Byramjee Jeejeebhoy Government Medical College in Pune, India. “We see that it has almost replaced all other variants in India, and we think the same thing will be followed everywhere.” 

In a study posted to the medRxiv.org preprint server, Karyakarte and his colleagues analysed more than 300 cases, from last December to early this month, and found that XBB.1.16 infections tend to cause mild symptoms similar to those from earlier Omicron variants, with few hospitalizations and deaths. “We didn’t see much,” Karyakarte says. The study has not yet been peer reviewed.

The World Health Organization declared XBB.1.16 a ‘variant of interest’ on 17 April. But whether it or another new variant will cause a spike in infections in a particular country will probably depend on the size and timing of the country’s earlier waves, says Tom Wenseleers, an evolutionary biologist at the Catholic University of Leuven in Belgium.