If the controls stop the flu by that route, why don’t they stop the coronavirus?

As the COVID-19 pandemic intensified, other respiratory illnesses became unusually quiet this year. Dangerous influenza and fear of COVID-19 “Syndemic“We have reached several cases of influenza and have not yet realized it. The lowest rate ever observed..

The low levels of influenza may reflect higher immunization rates. As seen in the United States, But far away, Hand wash Masking has probably played an even bigger role. But if these measures are so effective against influenza, why is SARS-CoV-2 still prevalent?

Reproduction number

Reproductive or “R” numbers measure how well the disease spreads and therefore how difficult it is to control. This number shows how many people are probably infected with one infected person.Seasonal views influenza Usually hovering Between 1.2 and 1.5On the other hand, the initial estimates of SARS-CoV-2 are 2 to 4.. This means that in “normal” situations (without masking, distance, and frequent hand washing), SARS-CoV-2 is about twice as infectious as influenza.

R should be reduced to less than 1 to prevent epidemic expansion. Seasonal flu Than SARS-CoV-2. If masking at a distance halves the reproduction of both diseases, SARS-CoV-2 will continue to spread and the flu will die and stop along that path.

But this is not really satisfying. Basically, I just said that SARS-CoV-2 spreads better because it infects more people. Why is SARS-CoV-2 difficult to manage?

Aerosol vs. droplets

SARS-CoV-2 and influenza spread in a similar way. Both can spread through contaminated surfaces, large respiratory droplets, and small respiratory aerosols. However, the relative importance of each pathway differs between the two viruses.

For influenza, contaminated surfaces and droplets are the main concerns. Hand washing, masking, and distance all do a good job of preventing this kind of spread.

SARS-CoV-2, on the other hand, is characterized by an explosive “super-diffusion event”, demonstrating the importance of aerosol-based diffusion. Recent research (not peer-reviewed) We support the idea that increased aerosol-based spread helps explain the different spread patterns of SARS-CoV-2 and influenza.

Masking, distance measurement, and hand washing are still useful, but aerosol-based diffusion makes it easier for SARS-CoV-2 to circumvent these measures.

Immunity

SARS-CoV-2 is a new virus for humans.In addition to the small level of Cross-immunity that previous infections with other coronaviruses may have given us (And this is not certain), our bodies are generally unable to detect and dodge infections from SARS-CoV-2.

Influenza is different. Since influenza is prevalent every year, we all have several influenza infections, each of which boosts our immunity to influenza. This immunity reduces the chances of spreading the infection and helps keep influenza reproduction low. Without this immunity, influenza reproductions would probably be close to SARS-CoV-2 reproductions. In the 1918 influenza pandemic..

Human behavior

That website Track SARS-CoV-2 reproduction numbers It shows something that deserves attention. Except for small peaks and dips, the number of views is hovering in many places around 1.

This probably reflects something about human behavior. When people see SARS-CoV-2 cases in the community, they adjust their behavior accordingly. Is the case expensive? Maybe we should stay tonight rather than go to a restaurant. Are they low? Maybe we could endanger children’s play dates.

Similar decisions are being made at the community level, with stay-at-home orders, business closures, and mask obligations alternating and lifted, depending on the severity of the outbreak. This eventually causes SARS-CoV-2 to reach its diffusion capacity limit.

This means that anything that spreads less than SARS-CoV-2 is likely to fall below the key playback threshold of 1. If this is the case, then with the absence of SARS-CoV-2, there should be a recurrence of other respiratory infections. The action restrictions will be lifted. This is certainly what happened in Australia: Pediatric respiratory virus RSV spike After the country lifted the blockade in October. And this was well off the normal time for the virus to spread.

Looking to the future

The good news is that the flu rate is currently declining, but stay alert. Influenza can spread in the months of summer as it has not wiped out the population and boosted immunity this year. Next winter’s flu season may also be unusually severe due to the lack of immunity from this year. Vaccination is becoming more and more important.

Low levels of influenza circulation can also affect the evolution of the virus. Predicting the evolution of the virus is the key to prescribing vaccines next season, so scientists need to closely monitor this.

On the other hand, it can be kept in mind that the measures taken to reduce SARS-CoV-2 are working, as evidenced by the reduction of other respiratory illnesses. Without these measures, COVID-19 would be an even bigger problem than it is now. Faced with both new and familiar infectious disease threats in the future, you can be confident that you have a powerful set of tools to help you stay healthy.

This article will be republished from conversation Under a Creative Commons license.Read Original work..