[ed. note: Michael Jorrin, who I dubbed “Doc Gumshoe” years ago, is a longtime medical writer (not a doctor) who writes for us a couple times a month about health issues, marketing, and trends. He does not typically focus on specific investment opportunities, but has agreed to our trading restrictions… as with all of our authors, he chooses his own topics and his words and opinions are his alone]
I guess I’m lucky, nothing worse than a runny nose and a dry cough, at least so far. But in my state of Connecticut, 1,360 people had been hospitalized with the flu as of February 3rd, and 63 people had died. Of those 63, 52 were over the age of 65. And one ten-year-old child has died.
Connecticut is about in line with the rest of the US. According to the Centers for Disease Control, influenza was widespread in 49 of the 50 states, the only exception being Hawaii, where it was described as “localized.” Localized flu was also the description for the District of Columbia and the territory of Guam, and in the US Virgin Islands, the flu was described as “sporadic.”
The CDC has no way of tracking how many total cases of flu there are in the US, since it is thought that a considerable proportion of people with flu do not seek medical attention, but just tough it out. However, they do track the percentage of patients who present to the health-care system with what they term an “influenza-like illness” (ILI), and by the end of January almost 8% of patient-doctor contacts nationwide were due to an ILI. That’s more than three times higher than the baseline, and the highest rate recorded at this time of year in the past 15 years. The highest rates nationally were in Texas and the immediately-surrounding states, where 12.6% of patients reported a flu-like illness.
So, in terms of pervasiveness, it’s definitely bad. But how about in terms of severity?
By mid-January, the hospitalization rate for flu was 31.5 per 100,000 population. That is lower than the rate during the 2014-2015 flu season, which reached 48.4 per 100,000 at the same point in January 2015, and went on to peak at 64.2 per 100,000. So perhaps this year’s outbreak is not quite as severe as outbreaks in some recent years. (The CDC confirmed that view on February 12th, saying that the 2014 – 2015 flu season was worse than the current outbreak.)
It has to be immediately acknowledged that comparing the severity of influenza outbreaks in different years is extraordinarily difficult. Do we count the total number of patients seeking care, or the total number of hospitalizations, or the total number of deaths? And do we scrutinize which population cohorts are most at risk from a flu episode requiring hospitalization, or at risk of death from flu? Some flu variants primarily affect young children who have not developed acquired immunity either through prior exposure to the same or similar flu variant or through a vaccine. Conversely, some flu variants are more likely to cause serious illness or death in older or more frail patients.
However we try to estimate the severity of this flu outbreak, it will not begin even to approach the global flu pandemic in 1918 – 1919, which is thought to have caused 675,000 deaths in the United States alone, and perhaps as many as 50 million deaths globally. That single disease outbreak by itself caused a dip in the otherwise steady growth in global population, similar perhaps to the effect of the bubonic plague in the 1340s. That pandemic, remembered as the Black Death, is estimated to have killed at least 30% of Europe’s population. It took more than a century for the population of the most affected regions to return to their previous levels.
The 1918 – 1919 flu pandemic killed about 2% of all the persons who fell ill with the disease. No other flu outbreak has come anywhere close to that level of deadliness. In contrast, the Asian flu pandemic of 1957 – 1958 caused about 1.5 million deaths globally, and was estimated to have a fatality rate of 0.13%. The Hong Kong flu of 1968 – 1969 killed perhaps one million persons globally with a fatality rate less than 0.1%. The so-called “Swine flu” epidemic of 2009 killed about 18,000 persons, with a fatality rate of 0.03%. So, based on those estimates, the 1918 – 1919 pandemic was about 15 times more deadly than the Asian flu epidemic, 20 times more deadly than the Hong Kong flu epidemic, and more than 60 times more deadly than the Swine flu epidemic. How our present outbreak will compare with those previous events remains to be seen, but so far, it doesn’t seem to be shaping up to be anywhere close to those epidemics.
A trend that you may have noticed is that the succeeding outbreaks do seem to be getting less deadly. Why might this be? Influenza has been around for a long time, and epidemics in which large numbers of people became infected and many died have been recorded since the 16th century, when an outbreak began in Russia, and spread to Europe where it killed more than 8,000 people in Rome and nearly exterminated the populations of several cities in Spain. Pandemics continued to occur throughout the 17th and 18th centuries, particularly affecting the inhabitants of cities. The severity of pandemics peaked with the 1918 – 1919 pandemic, and has been diminishing since that time.
Why might this be happening?
The likely answer is that the degree of immunity in the population at large has gradually been increasing, due to at least two factors. One is that with each succeeding influenza outbreak, whether a catastrophic global pandemic or merely a limited regional epidemic, more people have been exposed to some form of the flu virus and as a result have acquired a degree of immunity. A second factor (which some persons will vigorously contest) is that increasing numbers of people worldwide are getting influenza vaccinations, with the result that there are fewer hosts for the flu virus to affect and fewer infected individuals to transmit the virus.
Let’s look a bit more closely at immunity and how it works.
Immunity in general and in particular
A degree of immunity to organisms or toxins that have the capacity to inflict damage is common, and indeed essential, throughout the entire animal kingdom. For example, many non-human animals are entirely immune to a number of human diseases such as poliomyelitis, mumps, human cholera, measles, and syphilis. And conversely, humans are entirely immune to many animal diseases such as diste