Contrary to the popular opinion of some of the commenters here, I'm not just trying to scaremonger about the virus. Therefore, today I want to cover the most surprising trend in the last five weeks: the incidence of corona is decreasing in large parts of the world. Is this a seasonal phenomenon? Do the vaccines work? Dr.Roey Tsezana reviews all the alternatives
Contrary to the popular opinion of some of the commenters here, I'm not just trying to scaremonger about the virus. Therefore, today I want to cover the most surprising trend in the last five weeks: the incidence of corona is decreasing in large parts of the world.
Here are some examples:
- In the United States, the number of those diagnosed dropped from 315,000 per day on January 8, to 73,000 on February 19. The decrease in the number of those diagnosed was gradual and consistent throughout the intervening time[1]. All this, with a faltering vaccination campaign in which only 11.5 percent of the entire population was vaccinated[2].
- In the UK, the rate of those diagnosed dropped from one in eighty (about two weeks ago) to one in 115 (last week). In the same period of time, the infectivity of the virus in the UK decreased from 0.7-0.9 to 0.6-0.9. That is, every ten people who get infected with the virus, themselves infect between six and nine others. Similar results also come from the other three regions in the United Kingdom: Scotland, Wales and Northern Ireland.[3]. Currently, approximately 25 percent of all UK residents have received the first dose of the vaccine[4].
- In Spain, the rate of diagnosed cases dropped from two thousand per million people, to 310 per million people between January 25 and February 18[5]. This despite a rate of immunizers (at least the first dose) of approximately five percent.
- In many European countries we see that the rate of increase in morbidity is not great, and that the number of daily diagnoses remains more or less the same in the last month.
- In India, there was a decrease from 47 diagnosed cases per million people, to nine diagnosed cases per million people. And although it is rightly claimed that the data coming from India cannot be trusted, the general picture seems to support the possibility that there is indeed a widespread decrease worldwide in the rate of morbidity.
So what's going on here?
Before we continue, it is important to clarify that the trend is not valid worldwide. In Brazil, for example, we actually see an almost fourfold increase in the number of those diagnosed between November and February. Some place the blame on the new strain that is rampant there, possibly re-infecting the people who have recovered from the original strain of the virus as well. Right now, no one is sure.
Basically, this whole situation can be summed up in a few words: we don't know why this is happening.
But there are some guesses. If you want to read mostly how much we don't know, you can scroll down straight to the fifth guess, which unfortunately is also the best of them all at the moment.
First guess: behavioral change and closures
The past two months have seen lockdowns pop up all over the world as the virus reared its head again around October. Britain went into national lockdown at the beginning of January, for example, so it's no surprise that the number of people diagnosed in the United Kingdom has decreased[6]. Germany has closed large parts of the country - including schools, non-essential businesses, bars and restaurants - since November[7].
But the closures are not enough to explain the change in other countries. In the United States, no large-scale lockdowns can be found, and the response to the epidemic varies among the different sub-states. Nevertheless, a general decrease in morbidity can be seen there. Similarly, Spain chose not to impose a lockdown in recent months - and experienced a similar decrease in the rate of morbidity.
It is always possible that the world finally understood how to use masks and was convinced of their necessity. that people made more of an effort to maintain social distancing. But how to say gently? This explanation is simply not sufficient to justify the general decrease in morbidity, especially given the differences between the conduct of citizens in different countries.
Still, it is likely that the closures and behavioral changes led to a certain decrease in morbidity. But even if so - it is clear that this cannot be the only explanation.
Second guess: the virus is seasonal
Last October, a comprehensive review was published in the "Open Forum for Infectious Diseases", in which the researchers tried to understand how sensitive the virus is to the seasons. The researchers reviewed more than seven hundred different studies, and came to the conclusion that corona viruses in general reach their peak infectivity and spread during the winter season, and specifically in January and February in the Northern Hemisphere[8].
There is a good chance that SARS-CoV-2 is also seasonal, but if its infection cycle is similar to that of other corona viruses, then the mystery only gets stronger. After all, we would expect that precisely in the last two months the virus would spread more effectively in the northern hemisphere! As mentioned, we are witnessing the opposite phenomenon, and we do not know why. One can always argue that we don't know the new virus well enough - and that's certainly true - but we would still expect it to follow the spread patterns of other corona viruses. And even if not - at least he won't contradict them so clearly.
In short, even if the corona virus is seasonal, it is not enough to explain the decline in morbidity. exactly the opposite.
Third guess: partial immunity
This prediction is easy to misinterpret, so I ask you to read it carefully.
We know that people who have been infected with the virus and have recovered, develop antibodies that provide them with protection for at least several months[9]. We also know that in some countries - such as the United States - more than ten percent of the population has been infected, and there are hypotheses according to which the infection rate in the United States has already reached fifteen percent or more of adults[10]. These people are, in fact, vaccinated against the virus.
If there is one thing that characterizes those who contract the virus with a higher frequency, it is that they were more exposed to the virus in the first place. Not all of them, of course, but a large part of them. Medical workers, for example, are at increased risk of infection, as well as members of large families living in the same house. In some cases it is a matter of choice: in people who chose to take a conscious risk, and went out to meet others, eat in private restaurants and walk around without a mask outside the house.
If many of those people who were at high risk were infected, recovered and acquired immunity from the virus, then there is a chance that that group (and only that group) reached a high enough immunity rate to stop the spread of the virus through them. It is quite possible that those people were also the first to receive the vaccines in each country, and these helped them develop immunity to the virus.
I guess now we will hear the claim that "common sense" was right all along, and that we could have reached herd immunity. But this mechanism does not describe herd immunity, but the immunity of a very specific subgroup of the population. If everyone had taken to the streets in the past year, we would have seen much higher rates of infection and morbidity, and alongside them - also a jump in the death rate and the side effects following the disease.
And here is another small and important catch: remember I wrote at the beginning of the article that in Brazil there is currently an increase in morbidity? There is clearly a chance that variants of the virus can also deal with the immunity developed by the convalescents, and perhaps even with the immunity conferred by the vaccine.
In short, if the world reopens it is quite possible that the infection rate in the population will also rise again. And if we open the borders that are currently slowing down the spread of variants, we will not be surprised to find that those new variants of the virus will spread and infect an increasing number of people - including vaccinated people.
And if this explanation seems far-fetched to you, you should remember that even in the middle of the last year there was a lull in the spread of the virus in Europe and everyone calmed down - and right after that there was an even bigger wave than the first. So we should be careful in our interpretations of the reason for the decrease in morbidity, with the understanding that if we are wrong - then the virus will return in a big way.
Fourth guess: the vaccines
Let's start with a full disclosure: the decline in morbidity began in January, when the world's vaccination campaigns were still in their infancy, if at all. Despite this, the vaccines might have joined the other factors - the behavioral change and the partial immunity - and reduced the morbidity and the continuation of the infection. And yes, there is very good evidence that the vaccines - at least the Pfizer ones - really greatly reduce the infectivity of the vaccinated.
The vaccines can also explain the decrease in the rate of hospital admissions. They protect the vaccinated from developing a serious illness, so the risk of hospitalization and death decreases significantly. It is possible that there is a butterfly effect here: the vaccinations reduce the number of those hospitalized, the medical staff (who are themselves vaccinated, remember) become infected less and infect less other people, and thus the total number of infected people decreases.
Maybe.
And yet - we see the decrease in morbidity even in countries where vaccination campaigns are faltering, if they exist at all. So it is clear that even the vaccines are not enough to explain the general decrease in morbidity.
The fifth guess: We just don't know
And here we come to the fifth guess, and perhaps the best of all: we simply do not know why there is a worldwide decrease in morbidity.
I remind you that the SARS-CoV-2 virus is new, and we have never encountered it before. Is it possible that its properties are different from those we thought? It's always possible.
The virus's close cousin, the original SARS that began spreading in Asia nearly twenty years ago, disappeared on its own in no time. Why? We are not sure. Probably because the virus was too deadly, and was quickly detected by the health systems, so it was easy to isolate the infected. But no one is quite sure yet[11]. Maybe SARS-CoV-2 will also disappear by itself? Hard to believe, but maybe.
A little over a hundred years ago, the Spanish flu of 1918 struck in three waves that together resulted in the infection of approximately 500 million people, and the death of 50 million[12]. Why only three waves? We are not sure. Why did she disappear? Probably because it infected enough people to develop general immunity (and no, this is not an argument for herd immunity, unless you believe that ten percent of the population can be given up). But even in this we are not completely sure. Ecology of viruses is a complicated matter, and when it comes to a new virus - all the more so.
אז מה עושים?
So in conclusion, what do we do now?
First, I would be wary of assuming the virus is gone and won't come back. The masks, social distancing and closures may have contributed to the decrease in infection, but as soon as everything opens up again - it will come back in a big way. I remind you that this is exactly what happened in the last year in Europe, and also twice in Israel.
Second, it is quite possible that the world has been given a breathing space in the coming months, during which it is worthwhile to vaccinate as many as possible. This way, even if the virus returns to us, it will encounter widespread immunity. If we vaccinate enough people, there is even a significant chance that when the virus returns, we won't know it at all and assume we just went into a panic and vaccinated people for no reason. But he did. That's how it is sometimes.
Thirdly, and perhaps the most important: if the decision is in my hands, I would not reopen the borders without careful checks and even forced isolation of several days in hotels adapted to the matter. The renewed outbreak in Brazil suggests that new variants may bypass the vaccine, and if they reach Israel they will also harm the vaccinated. It's not the end of the world - it will be possible to develop new vaccines in a matter of months or weeks - but no one wants another shutdown.
What did my sergeant say in the army? "Hope for the best of everything, and expect and prepare for the worst of everything." This is our situation now. Let's hope for the best - and prepare for the worst.
Successfully!
[1] https://covid.cdc.gov/covid-data-tracker/#trends_dailytrendscases
[2] https://www.npr.org/sections/health-shots/2021/01/28/960901166/how-is-the-covid-19-vaccination-campaign-going-in-your-state
[3] https://abcnews.go.com/Health/wireStory/uk-covid-19-infections-falling-govt-mulls-easing-75998366
[4] https://ourworldindata.org/grapher/uk-covid-vaccination-doses-per-capita?tab=chart&stackMode=absolute&time=2025-08-03®ion=World
[5] https://ourworldindata.org/coronavirus-data-explorer?zoomToSelection=true&country=GBR~USA~ESP~ITA~BRA~IND~KOR®ion=World&casesMetric=true&interval=daily&hideControls=true&perCapita=true&smoothing=0&pickerMetric=location&pickerSort=asc
[6] https://www.gov.uk/government/speeches/prime-ministers-address-to-the-nation-4-january-2021
[7] https://www.dw.com/en/germany-coronavirus-merkel-and-state-premiers-meet-over-new-measures/a-56271628
[8] https://academic.oup.com/ofid/article/7/11/ofaa443/5929649
[9] https://www.theatlantic.com/ideas/archive/2020/07/could-covid-19-immunity-really-disappear-months/614377/
[10] https://www.wsj.com/livecoverage/covid-2020-11-27/card/vNkshCuxwSGLw7zkSx4z
[11] https://theconversation.com/the-original-sars-virus-disappeared-heres-why-coronavirus-wont-do-the-same-138177
[12] https://www.history.com/topics/world-war-i/1918-flu-pandemic; https://www.biospace.com/article/compare-1918-spanish-influenza-pandemic-versus-covid-19/
