SARS-CoV-2, like any rapidly replicating virus, adapts to the environment relatively easily. This was seen in the emergence of different variants last year. This has been produced by a specific situation: the absence of previous immunity, which has allowed high replication rates with the selection of viral variants, better adaptation to the environment, and easier replication.
Populations currently have a degree of immunity, either due to having suffered different waves of infection or due to vaccination; the rates of viral replication are lower, and, therefore, the risk of a variant appearing is lower. However, the situation throughout the world is not homogeneous. And, in a globalized world, what happens anywhere can move anywhere.
“In a globalized world, what happens anywhere can move anywhere.”
The situation in the UK is similar to other countries where vaccination with an effective vaccine has been extended to the entire population. Also, there have been different waves of the virus.
Several variants emerged when the viral replication rate, and the number of seriously infected, were very high. However, in recent months there have been increases in the number of symptomatic cases without having a great impact on the health system (Figure 1) due to a more transmissible but less severe variant. This situation is expected to remain steady in the coming months. The coexistence of different respiratory viruses (SARS-CoV-2, influenza, RVS…) will show up as epidemic outbreaks with cold-season increased incidence but without returning to the scenario of extreme severity experienced previously.
In summary, in the UK, vaccines have effectively reduced the impact of infections on hospitalizations and deaths, but emerging variants have been much more transmissible. The hospital admission rate and deaths involving COVID-19 are lower now than earlier in the pandemic, despite similar or higher infection levels (1).
Fig 1. SARS-CoV-2 reported cases in the UK across the pandemic (1)
From a world point of view at this moment, there are two situations that call attention. On the one hand, in the United States, there is a rapid growth of the XBB.1.5 subvariant, which already represents 40% of covid-19 cases. XBB.1.5 is a sub-lineage of XBB, which evolved from two earlier lineages of Omicron, with an additional spike change. It was first detected in the US in October 2022 and has been growing in proportion in the US and many countries worldwide since then. Increased prevalence of XBB.1.5 cases has eclipsed the previously dominant Omicron subvariant BQ.1.1 and BQ.1, which were offshoots of BA.5. (CDC).
The XBB 1.5 subvariant does not seem to have more serious features than the previous variants, and a catarrhal episode occurs with high fever and muscle aches and may require symptomatic treatment at some point. People with debilitating conditions will need more medical attention.
The situation in the USA in the coming weeks is expected to be one of growth in the incidence of these variants with a moderate increase in hospitalizations. Symptomatic treatment, reassuring the population, and carefully selecting the people who should go to hospitals can help improve control of the disease at this time.
Fig 1. Weekly SARS-CoV-2 cases in the United States reported to CDC (2)
On the other hand, China. The situation there is radically different. During the last two years, a Covid-zero policy has been chosen, which has meant that a large part of the population has not been repeatedly exposed to the virus (as has happened in other parts of the world) to this must be added the fact that vaccination has been carried out with vaccines (Sinovac or Sinopharm) whose efficacy is estimated at around 50% of those vaccinated.
In addition, WHO reports show that 87% of the population in China is vaccinated with two doses of local vaccines (Sinopharm and Sinovac-Coronavac), and only 55% have a booster dose. Above the age of 80, the figure drops to around 40%. This means that the situation in that country at this time can be comparable to that of the rest of the world after the first waves, and, therefore, it is possible that new waves with a large number of hospitalized people can be seen in that country.
Fig 2. Updated China situation to date 20th January 2023. Where COVID-zero policy shows how increases takes place once restrictions have been lifted (3)
At this time, the Chinese government has chosen to lift the restrictions and allow the movement of people and the consequent interaction. This has led to a very significant increase in cases. Many of these cases present with more severe forms of the infection because the population had not been confronted with the virus before, and the efficacy of the administered vaccine is less than expected.
A priori, this situation will be very particular to China, and the rest of the world, with its peculiarities, will be calmer regarding the SARS-CoV-2 infection.
But we must remain vigilant and carefully select who should go to a hospital or receive specific treatment in case of infection.
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