The numbers, both globally and in the United States (US), show a rapid decline in Covid-19 cases over the past month, revealing signs that the third wave, and hopefully the last big wave, is behind us. As scientists continue their work to better understand the reasons for the ebb and flow of Covid infections, which remain relativelyunknown, there is no guarantee that the most recent drop in caseloads will continue. Right now, we see a lot of good, even though it’s wrapped up in some not-so-good news.

First, the good news: The number of new infections has dropped more than45 percent over the past month to a seven-day average of about 84,000, and hospitalizations have dropped 39 percent over the past few weeks, according to the Centers for Disease Control. (CDC). Deaths have also fallen 23 percent over the past month – although more than 1,500 people have died on average over the past seven days.

The bad news: According to data from Johns Hopkins University, more than 363,000 deaths from Covid-19 have been reported this year, surpassing the 352,000 recorded in 2020. So yes, more Americans have died from Covid in 2021 than in 2020, and we still have more than two months until the end of this year. Given that the vaccine had been available to most Americans by mid-March and as well as significant advances in treating patients with Covid, a question – at least rhetorically – needs to be asked: why will 2021 be the deadliest pandemic year since 1919? A follow question begs for an answer: how many of those lives could have been saved by a simple vaccine that has been widely available to all Americans for most of the year? While the highly transmissible Delta variant became the dominant trend sweeping the nation, it spurred another wave that saw cases and deaths rise and many hospitals overloaded. Parts of the country where vaccination rates were lowest were hit particularly hard.

We may have seen the last big wave of Covid-19

The latest declines in Covid-19 cases are in line with a pattern many epidemiologists now know: a somewhat mysterious two-month cycle of Covid waves. Since it started in late 2019 in China, infections have often increased for about two months – sometimes due to a variant, like Delta – and then dropped for the next two months. The reasons for these cycles are not yet fully understood by epidemiologists. Suggestions that these cycles were probably only related to seasonality, or the flow and ebb of social distancing and mask use are most likely inaccurate. The proof is in the fact that bi-monthly cycles have occurred during different seasons of the year and even when human behavior was not changing in noticeable ways. This leads us to conclude that the most plausible explanations include a combination of virus biology and social networking practices. Developing variants of the virus are more likely to infect some people, but not others. The unvaccinated are the group in which the virus finds space to transmit and “spin” freely. Once the most vulnerable among us are exposed, the virus tends to recede, or as we have seen, regroup for another wave. These and possibly other factorscan determine if a virus or its new variants need about two months to circulate through a certain region. We have learned that human behavior plays a role in how significant an outbreak can be, with people often becoming more cautious as caseloads begin to increase. But social distancing alone may not be as important as public discussions often dictate; we tend to assign to ourselves too much control over the virus. We have seen recent declines, occur even as millions of American workers joined the workforce and millions of children gathered again in school buildings. Whatever the reason, Covid’s two-month “hills and valleys” cycles continue to occur. They are visible in both the global and US numbers. We saw that cases rose from late February to late April, then fell by the end of June, rose again by the end of mid-September, and have fallen since then.

The lagging indicators: hospitalizations and deathsare also declining

As we saw this past summer, Delta driven infections began in US southern states first in June and began to decline in August. In the rest of the US, it started in July and cases have started to fall in recent weeks. Cases have also dropped in children, despite the lack of vaccines for children under 12 years of age. The most encouraging news is that serious Covid infections are also declining. The number of Americans hospitalized with Covid has dropped about 25 percent since early September. Daily deaths – the lagging indicators – which usually change direction a few weeks after cases and hospitalizations, have fallen by 15 per cent since mid-September. These are the first continuous drops in deaths since the beginning of the summer. Importantly, help is also on the way for those unfortunates who contract the disease, as an antiviral pill has been developed by the Merck pharmaceutical company that may soon provide another weapon in the fight against Covid-19. The pill has been shown to reduce the hospitalizations and deaths by half for people infected with the virus.

The declining trend in Covid cases we are seeing now may not be a sure thing, as the two-month Covid cycle has not been scientifically proven. There have been many exceptions to the two-month cycle theories. But this uncertainty also means that the near future may be more encouraging than what some expected. And there are some legitimate and good reasons for the optimism that we are finally overcoming this pandemic. Through ongoing vaccination efforts, we now have more than 77 percent of Americans 12 years and older who have received at least one vaccination. Along with the possible authorization of the Pfizer vaccine for children ages 5 to 11, we will see a significant increase in the number of vaccinations this fall. Almost as important, something like half of Americans probably already had the Covid virus, perhaps giving them a good degree of natural immunity. Eventually, immunity will become so widespread – herd immunity – that another wave as large and damaging as the Delta wave was, would not be possible. Covid-19 will have proven to be one of the worst pandemics in modern times. In many ways, it will be an unnecessarily horrible pandemic. Of the more than 715,000 who have died from it in the United States alone, perhaps hundreds of thousands would have survived if they had only chosen to take the vaccine. This fact is what separates this pandemic from others, like the Spanish flu of 1918, for which no vaccine was available.

The worst is behind us

We know that Covid will not go away any time soon, at least not globally. With the ongoing global challenges of delivering sufficient vaccines and fast enough, the virus may continue to circulate for some time, perhaps years. But we also know that access to vaccines, especially in countries like the US, will turn Covid into a manageable disease, not much different from the common flu or cold. The last few weeks have shown that we are approaching a better future than the one that emerged over the last 2-3 months. We can say that whatever the coming months bring our way, the worst of the Covid-19 pandemic, appears to bebehind us.