If the Ro-the transition rate or the. number of people an infected person infects, the virus will spread. For instance, if one person infects four people in two weeks, those people can infect four people each, or sixteen people. The growth is always exponential. If the Ro is less than 1, the virus will eventually disappear.
It only takes one person to infect the world. COVID 19 started with one person in China.
Mitigation is the process of reducing the spread. At one time, here in Israel where I live, we got Ro down to 0.6, but that required an almost total lockdown, closure of the borders, and careful testing.
Many more people likely have the virus than is reported. Here in Israel, we see that about 2.5% of people tested for antibodies have had the virus. That is almost ten times the reported number. These people had no or almost no symptoms. However, herd immunity will take a long time unless the Ro is allowed to go up to a large number. That would not be wise because the result would overwhelm the medical system and result in an increase in the mortality rate.
Mortality in Israel is very low. We have had 300 deaths out of 18,000 confirmed cases. This is about 0.015%. Dying is not the only number to be concerned with, as many patients that do not die are left with issues like lung scarring. The USA has 353 deaths per million. Israel has had one-tenth of that or 33 per million. Why is that? There are man factors that influence this statistic. Demographics are critical. Death occurs almost exclusively in patients with comorbidities like diabetes, lung disease, Obstructive Sleep Apnea, and obesity. Many of these are correlated with age. Being old by itself is not the issue. It is just that many more older people have other things wrong with them. The average age in Israel is 30.2 years. In the USA, it is 37.7 years. About 14.5% of the USA population is over 65 years old. The number of people in Israel over 65 is not much different. However, Israel was able to keep the older substantially safer. There is many reasons for this which I won’t go into here.
A key regarding mortality is the ability of the hospital system to deal with patients with severe COVID 19. In this regard, we can’t look at the national numbers for the USA. Israel is a small country about the size of the San Francisco Bay Area. The USA is vast. Averaging places with little disease and those with lots of the disease can be very misleading.
One of the critical factors in understanding the spread of the disease in any given location is how early actions were taken to mitigate the spread of the disease. Israel closed its borders very quickly, although there was a delay of a week in closing the USA border do to interference by the Trump Administration. It is estimated that 70% of the cases can be traced to people who entered Israel from the USA during that extra seven days.
If two locations had the same program to reduce the spread and the same population, but one started with 100 active cases and the other with 1000 active cases, it is likely that everything that happens later would be identical. However, in the second case, there would be ten times as many people. That is why the delays in mitigation in many states in the USA resulted in many more cases. It has been estimated that if locked downs had happened a week early a 60% reduction in the number of cases could have resulted. There would have probably an even more significant reduction in the number of deaths. It was, of course, much easier to lock things down in Israel since it is easy to close the border. Israel is a very family-oriented society, and older people are well taken care of. Everyone pretty much has health insurance/
I think one of the biggest differences is how the initial testing was done. In the early days, those suspected of having the virus were tested in their homes. If they were tested outside, there was a great effort taken to make sure they did not expose others. Evidently, in the USA, many people that suspected they had COVID 19, went to emergency rooms. So if you have ten people in the room that suspect they might have the virus but only one that does, you may have created nine more that are now positive. Isolation of those that are infected is critical. Israel set up hospitals only to treat COVID 19 patients. Staff would not mix. The staff is tested every week.
Contact tracing is critical. Israel used technology to trace cell phones so they could alert people that had come into contact with people that tested positive. I have such an app on my phone.
Quarantining is critical. If someone has been in contact with COVID 19, they have to be quarantined for two weeks. Also, if someone did come into Israel from abroad (Israeli citizens primarily), they had to be in quarantine for two weeks.
The USA has a much more challenging situation. USA citizens can fly to any of the 50 states without being tested or quarantined.
We have learned that wearing masks can significantly lower the probability of transmission. I guess that it can reduce the transmission rate by at least 50%. I can understand people in Israel and the USA that do not wear masks when they are in the presence of others nearby. They are either ignorant or selfish or both. But it takes real leadership to explain this to people. Unfortunately, the USA does not have that kind of leader, sadly.
I think the Ro can be reduced to close to 1 if masks, social distancing, and hygiene are applied. It is a small price to pay for saying the lives of so many and for being able to open up the economy.