Will a peak appear every 6 months become the norm?
Written by | Yan Xiaoliu
Source | "Medical Community" public account
According to a report by the World Health Organization (WHO) on April 27, the number of new COVID-19 confirmed cases and deaths worldwide continues to decline. Compared with the previous week, the number of new confirmed cases fell by 21%.
But South Africa is an exception.
On the day of the WHO report, the South African Centre for Epidemiological Response and Innovation (CERI) forwarded a statement from Ridhwaan Suliman, senior researcher at the South African Council on Scientific and Industrial Research, with a warning: "Wave 5 has arrived. Please be careful. ”
At this time, it is only more than 3 months since South Africa came out of the last wave of the epidemic.
Image from Twitter
On April 29, local time, Redwan Suliman posted on social media "Twitter" that due to the Opmi Kejung asian BA.4 and BA.5 pandemics, the number of new confirmed cases in South Africa increased by 120% compared with the previous week. The number of new infections doubles every 6 days.
Gauteng Province, which has been repeatedly hit hard by the epidemic, has once again become the "epicenter". The province has a population of 25% of South Africa. In the past two weeks, the number of new infections has doubled every 4.8 days.
Redwan Suliman said this may indicate that South Africa's "immunity levels" and "infection numbers" are decoupled. That is, on the basis of high antibody positivity rate and population immunity, the transmission of the virus has not been interrupted.
Photo caption: Daily positive rate curve during the pandemic in South Africa. /Twitter Ridhwaan Suliman
"Vaccination rates in South Africa are low, mainly relying on natural infections and the formation of an immune barrier. For a long time, local outbreaks have been cyclical. To find out the antibody positivity rate, infection rate and re-infection rate of the general population, the relevant analysis will have global reference value. Jin Dongyan, a professor at the School of Biomedical Sciences at the University of Hong Kong School of Medicine, told the "medical community."
Two indicators indicate a resurgence of the epidemic
"We are closely watching South Africa." Jacob Lemieux, an associate professor at Harvard Medical School and an infectious disease physician at Massachusetts General Hospital, said two important indicators have changed.
First, the positive detection rate of new crown, which is regarded as a bellwether for the speed of virus transmission, continues to rise.
On April 26, Gauteng's positive detection rate rose to 20.2 percent, the highest level since January. In contrast, on April 4, South Africa's COVID-19 positive detection rate was 5.4%.
"Nucleic acid or antigen detection is down 5 to 10 percent, but detection rates are increasing. This suggests that there may be a large number of infected people who have not been detected. Redwan Suliman said.
On the other hand, wastewater analysis, one of the "early warning systems for COVID-19", also suggests a comeback. In Gauteng, KwaZulu-Natal, Free State and the Western Cape, the odds of COVID-19 detected in wastewater samples are on the rise.
Currently, the number of hospitalizations in Gauteng, Free State and KwaZulu-Natal provinces has increased. Gauteng province admitted 83 patients in intensive care, with a 59% increase in hospitalizations, but still below baseline. Ridwan Suliman believes that given the lag between infection and death, it is not yet possible to assess the severity of the current outbreak.
"All indications are that infection and severity may be decoupled." Professor Marc Mendelson, former president of the International Society of Infectious Diseases and expert in infectious diseases at Groote Schuur Hospital in South Africa and head of the Department of Infectious Diseases and HIV Medicine, said.
Picture caption: The blue line is the number of infections; the red line is the number of hospitalizations; the green line is the number of deaths. /Twitter Ridhwaan Suliman
Déjà vu decoupling
Redwan Suliman said the current growth curve of the epidemic in South Africa is "familiar". The decoupling of "immunity level" and "number of infections" reflected in it is worth paying attention to.
According to Our World in Data, South Africa has confirmed more than 3.7 million cases of COVID-19, or 6.2% of the country's total population.
"In Gauteng, population immunity is 80%-90% based on previous natural infections and vaccinations. But it is clear that, once again, high levels of immunity have not stopped a new wave of outbreaks. Redwan Suliman said.
The last time there was a "decoupling" was when Omikeron became the main epidemic strain in South Africa, causing the fourth wave of the epidemic. Thankfully, due to the decline in the pathogenicity of Omikejong, the number of infections and severe diseases and deaths of this round of epidemics have also been decoupled.
Tulio de Oliveira, a virologist at Stellenbosch University in South Africa, is the director of CERI and is known worldwide for being the first to report on the variants Beta and Omikron.
He said the rapid rise in the curve of infections in South Africa was "also very similar to the beginning of the Omiljung epidemic".
Photo caption: Data as of April 28. The red curve is the 5th wave of the epidemic in Gauteng Province, South Africa; the purple is the 4th wave of the Hauteten outbreak in The Ohmi kerong Epidemic. /Twitter Ridhwaan Suliman
According to Tulio de Oliveira, part of the reason may lie: "This time, South Africa's opponents are The Aumi-Kjungyan BA.4 and BA.5. ”
On April 14, local time, the World Health Organization (WHO) reported that it is paying close attention to some Opmi-Kronian viruses, including BA.4 and BA.5.
Both strains were first seen in South Africa and subsequently reported in many countries around the world. As of April 29, local time, the detection rate of BA.4 and BA.5 in sequencing cases in South Africa reached 60%-75%. Most samples collected at multiple wastewater sampling sites in Gauteng can detect BA.4.
On April 29, local time, CERI released a preprint study saying that compared with the Aumique Jungian BA.2, the daily growth advantages of BA.4 and BA.5 were 0.08 and 0.12, respectively. Compared to Omikeron, the daily growth advantage of BA.2 is 0.07.
That is to say, BA.4 and BA.5 are more disseminated than Omikeron and BA.2.
The article analyzes that this growth advantage may be contributed by multiple factors. For example, compared with Theomexon and its lineage variants, the spread and immune escape ability of BA.4 and BA.5 have been enhanced. Also, the fourth wave of the outbreak caused by Omi kerong is 4 months old, and the immunity generated by natural infections has begun to weaken.
In addition, on the night of April 4, South Africa ended the 750-day national disaster state. Since then, only some "transitional" epidemic prevention measures have been retained, such as the need to wear masks indoors and international travel restrictions, for a period of 30 days. After the relaxation of epidemic prevention, the movement of people has increased, which has also contributed to the spread of the virus between people.
Jacob Lemieux and others believe that the resurgence of the epidemic in South Africa has built a new crown immune barrier and poured cold water on it. "Many people have quantifiable immunity, but the growth rate of the number of cases has not declined. This either indicates a deficiency in the degree and breadth of immunity, or that viral mutations lead to stronger immune escape. ”
Tom Wenseleers, an evolutionary biologist and biostatistician at the University of Leuven in Belgium, points out that the best note for the 5th wave of the outbreak in South Africa, or "endemic epidemics", is that there is a peak every 6 months, accompanied by a significant increase in morbidity and mortality.
Image courtesy of Twitter TWenseleers
Professor Jin Dongyan disagreed on this. He told the "medical community" that there were many issues in South Africa that were "still unclear". For example, in wave after wave of outbreaks, what is the proportion of re-infections. Among them, the history of natural infection and the history of vaccination account for each proportion. Especially in this round of the epidemic, how many people have been infected with Omi kerong before.
The answers to these questions may be the key to revealing whether the outbreak is changing cyclically.
Citing several outbreaks in Hong Kong, China, as an example, he explained: "The Hong Kong SAR was hit hard for the first time in the fifth wave of the epidemic, and the number of infections soared. At present, the peak and epidemic evolution around the world are different. ”
When will the vaccine be upgraded?
But South Africans are too lazy to talk about COVID-19.
According to the Social Listening and Information Epidemiology Team of the South African Ministry of Health, in the week of April 18, South Africans posted on social media "Twitter" to discuss the popularity of the new crown vaccine, which dropped by 50%. Over the same period, participation in social media "Facebook" also fell by 60%.
Meanwhile, vaccination rates in South Africa have stagnated. According to the country's health department's original design, the vaccination target of 67% of the entire population should be reached by December 2021.
As of 24 April 2022, only 44.62% of South African adults were fully vaccinated. In people aged 34 years or younger, the full vaccination rate is about 31%.
More than half of adults are fully vaccinated in only 3 provinces: Free State, Western Cape and Limpopo.
A recent survey showed that there are not many factors that motivate South Africans to vaccinate, and that giving cash is useless. Only a few people choose to be vaccinated in order to find a job or keep a job.
Photo caption: Statistics on weekly vaccinations in South Africa. /Business Insider
According to Tom Winslers, while continuing to promote vaccination, more attention should be paid to vaccine upgrading.
"It's as if medical institutions haven't accepted the fact that covid-19 evolves 2.5 times faster than the fastest-evolving flu virus. Well, the COVID-19 vaccine should be updated twice as fast as the flu vaccine. ”
Image courtesy of Twitter TWenseleers
Source:
[1] South Africa enters fifth wave of Covid-19 pandemic. Africa News
[2] South Africa Likely to See Fifth COVID Wave.Medpage Today
[3] Twitter Ridhwaan Suliman
[4] South Africa:Wastewater Testing Shows Signs That Covid-19 Fifth Wave Looms.All Africa
[5] Omicron subvariants rise in prevalence as South Africa’s positivity rate jumps overnight. Daily Maverick
[6] Subvariants cause for alarm,hybrid immunity hard to beat. The Harvard Gazette
[7] South Africa has lost interest in Covid-19–just in time for a fresh wave of infections. Business Insider
[8] Continued Emergence and Evolution of Omicron in South Africa:New BA.4 and BA.5 lineages.medRxiv.MEDRXIV-2022-274406v1-deOliveira:(2022).
Source: Medical community
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