Wikipedia:Reference desk/Archives/Science/2020 May 20

= May 20 =

CoViD-19 deaths per capita, China vs. some western countries, why difference?
Italy I can understand because of the early outbreak, the UK and USA I can understand because of their leaders, and Sweden has made a clear choice; but why countries like the Netherlands?

The Netherlands has a population of about 17.5 million, and $5,715$ CoViD-19 deaths. China has a population of about $1.4$ billion, and $4,634$ CoViD-19 deaths.

Why are the deaths/capita so much worse in some western countries, despite all the warning, time, and wealth?

Is it that:
 * 1) some western governments would rather sacrifice more of their older population for short term financial gain, by refusing to do a real lockdown like in Wuhan?
 * 2) China is lying about their number of deaths?
 * 3) biology, like older populations in Europe, or vitamin D deficiency?
 * 4) other? -- Jeandré, 2020-05-20t09:33z


 * In the case of Europe, see: Measuring excess mortality: England is the European outlier in the Covid-19 pandemic. Alansplodge (talk) 09:59, 20 May 2020 (UTC)
 * So the excess mortality in China has not been published, and that could make China's figures much worse? How would the recent mass-testing in Wuhan influence confidence in China's numbers? (PS: the South African partial stay-at-home order reduced Easter road accidents from 162 last year to 28 in 2020. It also reduced homicides from 1542 last year to 432 in 2020 over the same first 3 weeks of April, compared to 65 CoViD-19 deaths by April 22.) -- Jeandré, 2020-05-20t10:12z
 * I wonder what China's MMR vaccination strategy has been? --jpgordon&#x1d122;&#x1d106; &#x1D110;&#x1d107; 14:44, 20 May 2020 (UTC)
 * A large factor is that different countries have different criteria for reporting COVID-19 deaths. Some countries report a person with a tested infection who dies in a traffic accident as a COVID-19 death.  Then there are less clear cases: someone with a cancer and a COVID-19 infection dies - was that due to the cancer or the virus?  COVID-19 has a lot of co-morbidity - someone with a pre-existing condition is way, way, way more likely to die - which of the two (or more) conditions is the real killer?  When an elderly person dies, dífferent countries have different standards for testing and reporting for COVID-19 deaths.
 * Relly important: "number of cases" does not equal "number of infected". Rather, it means "how much are we testing in this country".  Simply stop testing and you have no "cases" or deaths due to the virus!
 * These dumbed-down-for-the-unwashed-masses numbers and maps are highly misleading. Be smart and don't believe them.  85.76.71.1 (talk) 15:22, 20 May 2020 (UTC)
 * " Some countries report a person with a tested infection who dies in a traffic accident as a COVID-19 death". That's a claim I see a lot of people on the internet making, but I've never seen any evidence presented to support this (and in many case, as here, its not even stated which country they are talking about). Iapetus (talk) 09:17, 21 May 2020 (UTC)
 * "Germany, Luxembourg, South Korea and Spain count all deaths of those who have tested positive for COVID-19" - assuming that statement is literally true. Similar statements can be found in other newspapers. 85.76.71.1 (talk) 11:04, 21 May 2020 (UTC)
 * Note the Russian method of counting untested Covid-19 fatalities as "community-acquired pneumonia" . Alansplodge (talk) 15:45, 20 May 2020 (UTC)
 * Why are you comparing number of deaths to total number of population? If a country had better success containing the outbreak, for example, we wouldn't expect the total number of deaths to be as high compared to the total population as a country that did not contain it well. There is a reason that mortality rates are described as deaths per infected, and not deaths per capita. --OuroborosCobra (talk) 18:00, 20 May 2020 (UTC)
 * That's the very point. A country that has significantly lower deaths per population than another country - assuming both are exposed to the same degree and their reporting protocols match up - tells us immediately that the first country is doing something that the second country should be considering. Australia reached 100 deaths yesterday. That's not 100 per day, but 100 in total. Now, we have a smaller population than the UK, for example, so it's useless and dumb to compare our raw toll with theirs. The only sensible basis of comparison is deaths per population. The UK has had about 419 deaths per million. Australia has had 4 deaths per million. Need I say more?  --   Jack of Oz   [pleasantries]  23:08, 20 May 2020 (UTC)
 * What about COVID-19 deaths as a percentage of those who were confirmed to have contracted it? ←Baseball Bugs What's up, Doc? carrots→ 01:28, 21 May 2020 (UTC)
 * If a country tests very few people, you can get over 100% mortality. If a country tests everyone, you get very low mortality.  There are estimates that there are 5-10 times as many untested infected than tested in most countries.  Calculations, charts, and comparisons of number of positive tests are mostly misleading random number generators.  85.76.71.1 (talk) 11:09, 21 May 2020 (UTC)
 * Yes, but if you test nobody, you can claim people are dying of other causes, and claim your country is run by a stable genius who is dealing with the disease perfectly. -- Jayron 32 12:21, 21 May 2020 (UTC)
 * Please everyone, let's just /thread here. 85.76.71.1 (talk) 15:41, 21 May 2020 (UTC)
 * Going back the to the original question, it seems like a factor must have been the "dose" of initial cases a country got in the first place, the number of people who arrived in the country with coronavirus before travel was limited. Hubs of global travel with major airports and business centres, notably London and New York, have often been particularly badly affected. Countries with vast rural regions like India and the USA have often had very low spread outside the big cities. Blythwood (talk) 16:23, 21 May 2020 (UTC)
 * And both those places feature high population density - see High Population Densities Catalyse the Spread of COVID-19 and some urban deprivation - see COVID-19 more common and severe in urban and most deprived areas. A perfect storm. Alansplodge (talk) 10:39, 22 May 2020 (UTC)
 * And in addition, it must be stressed that there's good reason to believe it is just random, or driven by factors that aren't immediately obvious. One tiny, isolated county in rural southwest Georgia in the USA has one of the USA's highest case rates. Nobody knows why. In the UK, the very isolated rural county of Cumbria has a higher case rate than many central London boroughs, and the biggest outbreak isn't in the tourist hotspot areas. Reports suggest this is a combination of aggressive testing and outbreaks in care homes. In Canada, the nearby and similar cities of Calgary and Edmonton have totally different disease rates-partly perhaps driven by an outbreak at a meat-packing plant. I myself think about how many old people (especially older ladies) I knew growing up born in the 1910s and 1920s saw it as totally normal to kiss the host when arriving and leaving social events, and looked at you as a spoilsport if you didn't go all in, so to speak. If this epidemic had come fifteen years ago when more people from that generation were alive, I think it might have been much much worse. Blythwood (talk) 18:17, 22 May 2020 (UTC)

Transformer winding voltage ratio, and the input frequency
Does the frequency of the input current determine/affect the output voltage for a given winding ratio? ZFT (talk) 22:49, 20 May 2020 (UTC)
 * Ideally, no. But transformers become inefficient outside their intended range of operation. Jc3s5h (talk) 23:07, 20 May 2020 (UTC)


 * Yes. The peak output voltage is directly proportional to the maximum rate of change of magnetic flux through the secondary windings. And, of course, the maximum rate of change of magnetic flux is directly proportional to the frequency at which the transformer is operating. Dolphin ( t ) 13:29, 21 May 2020 (UTC)
 * No. As stated in our Transformer article, for a sinusoidal input, the RMS EMS is
 * $$ E_\text{rms} = {\frac {2 \pi f N a B_\text{peak}} {\sqrt{2}}} \approx 4.44 f N a B_\text{peak}$$
 * When considering ideal circuits, the input voltage is provided by a sinusoidal voltage source, which will force the voltage at the transformer input terminals to be a the given voltage, no matter what. Therefore, as the frequency rises, the peak magnetic flux density will reduce to make the equation true. The other winding will have this same magnetic flux density flow through it, and the induced voltage will be determined by the turns ratio. (Ideally readers would consult the reliable sources mentioned in the "Transformer" article.) Jc3s5h (talk) 15:09, 21 May 2020 (UTC)
 * So is this article in error, or am I misunderstanding it? ZFT (talk) 19:05, 21 May 2020 (UTC)
 * may be correct. I look forward with interest to responses from other Users. Dolphin ( t ) 22:26, 21 May 2020 (UTC)
 * The Electrical Blog article is in error. Notice it contains the phrase "Voltage of a transformer at a given flux density increases with frequency". But the flux density does not remain constant; if the input voltage is kept constant while the frequency decreases, the flux density decreases. This is why aircraft have used 400 hz; the lower flux density associated with the higher frequency allows transformers to be smaller and lighter; obviously minimizing weight is important on aircraft. Jc3s5h (talk) 00:23, 22 May 2020 (UTC)
 * At Transformer it implies strongly that the EMF from the secondary is proportional to the turns ratio and the input voltage; and nothing else. Therefore we must conclude that the output voltage is unaffected by the frequency at which the ideal transformer is operating. This may not be exactly accurate for very large variations in frequency but the ideal transformer is not intended to take account of such large variations. Dolphin ( t ) 02:23, 22 May 2020 (UTC)