Early in the pandemic, public health officials warned that there is no prior immunity from the novel coronavirus. The global data on infections has backed that up and is a grim reminder of how little is known about the disease. In only nine months, more than a million lives have been taken among the 37 million who have been infected.
Can people become immune to infection? And does herd immunity work?
Now, signs of a second wave have arrived in the United States and in Europe, leading to growing concern about the health care system’s ability to absorb the increase in patients.
In the U.S., the human toll is mounting. The virus continues its spread into the upper Midwest and Rocky Mountain regions, and into college towns. Infections are also rising once again along the East Coast after declining from an early peak. The RSM model anticipates the number of infections to surpass 8.6 million over the next two weeks.
The immunity question
The current strain of novel coronavirus is only one of a category of virus that routinely circulates the globe. Some are more severe than others. But a central riddle of the novel coronavirus is immunity: Can people become immune to infection? And does herd immunity work?
In a study of four confirmed cases of COVID-19 reinfection, two of the patients suffered worse consequences than in the initial infection. In addition, analysis of a reinfected patient in Nevada indicated a strong likelihood that his second infection came from a separate strain of the COVID-19 virus.
“Herd immunity requires safe and effective vaccines and robust vaccination implementation,” The Lancet writes.
The Lancet article said, “Due to the paucity of broad testing and surveillance, we do not know how frequently reinfection occurs among individuals who recovered from their first infection.” It concludes that the presence of “reinfection cases tell us that we cannot rely on immunity acquired by natural infection to confer herd immunity; not only is this strategy lethal for many but also it is not effective. Herd immunity requires safe and effective vaccines and robust vaccination implementation.”
A separate article published in The Lancet suggests that further validation is needed to determine the existence of cross-protective effects from exposure to low-level strains of the novel coronavirus.
Put another way, does exposure to the flu or the common cold – which are all strains of coronavirus – give your body a head start on resisting the COVID-19 disease? (One point to note: There were only 10,000 total cases of SARS and MERS infections, which are the closest relatives of the novel coronavirus. The low number of infections to those severe diseases implies a minimal potential protection against the global pandemic. So the scientists are looking for clues elsewhere.)
Another study, published in Science, finds that the extreme variability of the response to the COVID-19 disease might be associated with the ability to respond to seasonal coronaviruses. But while the study found that people with a more severe case of COVID-19 exhibited weaker antibody responses to prior infections, that weak response was possibly influenced by demographic factors.
As to the variability of the disease’s severity, the article notes, “While some individuals remain entirely asymptomatic, others experience fever, anosmia” – or loss of smell – “diarrhea, severe respiratory distress, pneumonia, cardiac arrhythmia, blood clotting disorders, liver and kidney distress, enhanced cytokine release and, in a small percentage of cases, death.”
The study suggests that while “[secondary] responses to seasonal coronaviruses may influence the antibody response to SARS-CoV-2,” severity of the COVID-19 disease “is correlated with advanced age, sex, ethnicity, socio-economic status,” among other factors. Among those hospitalized with COVID-19, “higher age, male sex and non-white ethnicity groups were significantly overrepresented,” the study said.
To a non-medical observer, the demographic characteristics of those who have contracted the COVID-19 disease help explain its unequal impact on socioeconomic classes, and public policy response. Although COVID-19 can kill the healthiest or the richest people, those at the bottom of the socioeconomic ladder have suffered disproportionately.
This cuts across all geographies, from cities to struggling rural areas that have limited access to health care.
As to the spread into the West, The Bismark Tribune reported record numbers of infections in North Dakota and growing concerns as hospitals approach capacity. And in South Dakota, the Department of Public Health reported substantial community spread in most counties, resulting in a record number of infections.
A national pandemic
More than eight million Americans have been infected by the novel coronavirus as of the third week of October. (This is according to the Worldometer database, which consistently records higher rates of infection and death than other databases.) The rate of new infections has exceeded 50,000 per day as shown in the first figure below.
At the current rate of spread, the RSM model looks for the total number of U.S. cases to reach 8.3 million in the current week and 8.6 million in two weeks (see the second figure).
The third figure shows that the total number of U.S. deaths attributed to the coronavirus is 220,000, with the number of deaths averaging 710 per day. That number is down from the 2,200 per day at the height of the outbreak in April and 1,000 per day just weeks ago, but remains an unsettling reminder as the winter months approach.
Infections increased in 43 states in the latest week, and not only in the northern tier. Weekly increases of 70% in New York prompted local shutdowns of businesses in areas of Brooklyn, while New Jersey officials discussed plans to contend with a second wave of infections.
The first figure shows the spread of the infections from the six states with major metropolitan areas (Massachusetts, New York, New Jersey, Pennsylvania, Illinois and California) where the initial outbreak peaked in April. The virus’s spread then accelerated in states across the Sun Belt and Midwest, where infections peaked after the July 4 weekend.
Infections in the six states with major metropolitan centers are rising again at an average rate of 9,900 cases per day. Infections in all other states are rising at a more alarming rate and now account for 39,200 newly reported cases per day.
Deaths attributed to coronavirus infections (shown in the second figure) peaked in mid-April. There was a second peak in early August after cases had spread across the South and Southwest. The combination of a younger cohort of infected people (nursing homes had been locked down) and improved treatment has helped lower the overall mortality rate.
Average weekly growth rate
In the following table, we show the state-by-state weekly growth rate of infections since:
- The reopening of local economies around May 1, which was likely to increase the exposure of the public in commercial locations
- Summer’s unofficial opening on the Memorial Day weekend, which increased exposure as people looked for a respite from isolation
Because of the inconsistency of reporting by states, and the haphazard all-too-human spread of the virus, we are looking at the overall spread of the virus in our rankings.
Of the six major states, California, with a 2.6% average weekly growth rate, Pennsylvania (2.1%) and Illinois (1.0%) are reporting rising cases since Memorial Day. While cases in New York, New Jersey and Massachusetts are decreasing, those improvements have decelerated and are cause for alarm as winter approaches.
Overall, 42 states are reporting positive average weekly growth rates since the Memorial Day weekend, as listed in the table below.
For more information on how the coronavirus is affecting midsize businesses, please visit the RSM Coronavirus Resource Center.