Herd immunity? Is it the answer? I have also heard it said COVID-19 is just a cold or the flu, the seriousness of this has been hyped. But has it?
Pandemics occur when a new or novel virus or subtype begins to spread easily. Viruses arising from animal sources and crossing over to humans are particularly dangerous as it is indicative of changes in the virus, creating a subtype. SARS, MERS, and Ebola all started in animals. Novel viruses and subtypes are highly contagious and deadly because we have no immunity, our immune systems have not encountered the virus before.
The COVID-19 virus was originally called SARS-CoV-2. Coronavirus is a general term for a group of viruses that can infect humans. Seven have been identified since the mid-1960s. Four of them commonly affect humans and range from illnesses like the common cold to pneumonia. The remaining three are MERS-CoV, SARS-CoV, and the most recent SARS-CoV-2 or COVID-19. MERS is Middle East Respiratory Syndrome identified in Saudi Arabia in 2012 and spread to 27 countries. To date confirmed MERS cases are a little over 2,500 with 866 deaths. Most of the cases stayed within the Saudi border and two were found in the United States, likely a result of travel from Saudi Arabia.
SARS is Severe Acute Respiratory Syndrome, a deadly viral pneumonia caused by the SARS-CoV coronavirus. It was first identified in Asia in 2003. Panic ensued and the national news networks carried footage of people walking around in masks. SARS spread to 26 countries, infected 8,000 + people and killed 774. Since 2004 there have been no reported cases. COVID-19 killed nearly three times as many people in the first eight weeks.
Both SARS and MERS share commonalities with the COVID-19 virus, but there are significant differences. Comparing transmission and death rates, COVID-19 is more virulent and has higher mortality rates. One month into the SARS outbreak, only five people had died, however, COVID-19 had killed 213 people in that same time frame. And, the COVID-19 death toll topped SARS deaths on February 8, 2020, long before most of us were on a first-name basis with the new coronavirus. Within the first three months after COVID-19 arrived on the scene close to 1 million people were infected and 50,000 died. Why?
In epidemiological terms, the COVID-19 virus has a reproductive number of 2.2 or higher, meaning each person with COVID-19 infects at least two other people. Infectious disease experts tell us in order for the COVID-19 virus to be effectively contained the reproductive number needs to be brought down to less than 1. The reproductive number for the 1918 Spanish flu pandemic was 1.8 and it killed 50-100 million people, which is about one-quarter of the world population today. By contrast, the reproductive number of ordinary influenza is 1.28 and can result in 10-20% of the population contracting flu during the flu season with a death rate of about 0.9%. In the early days of COVID-19, the long-term care facility in Washington state experienced a death rate of 30% in its resident population, certainly not typical for long-term care facilities during flu season.
Both SARS and MERS had high reproductive and mortality rates however the significant difference between SARS, MERS, and COVID-19 is in their incubation and transmission rates. Unlike COVID-19, SARS and MERS incubation periods were longer and neither transmitted easily. And, of greatest import, those with SARS and MERS were most infectious when they were too ill to remain in the community so it was more easily contained in hospital isolation rooms. Longer incubation periods and lower transmission rates gave infectious disease experts the opportunity to eradicate the viruses through contact tracing, isolation, and strict infection control measures in the hospital setting.
So let’s talk about herd immunity, a concept popping up in Facebook articles more and more often. Herd immunity is essentially a scientific concept, and shouldn’t be considered a means to deal with a deadly virus, at least not this early in the game. Simply put, allow a virus to spread unchecked and eventually it will die out because most will have developed an immunity. Infectious disease experts view herd immunity as their worst-case scenario estimating that within this year more than 60% of the world’s population will be infected, however, the Facebook misinformation does not take into account the consequences of such drastic measures. Hospitals would be even more overwhelmed, ventilators and healthcare workers would be in even shorter supply, and death rates would skyrocket. We will get to a point when herd immunity will work but it won’t be until at least 66% of the population are immune – either from having had the virus or through vaccination.
Little is still known about COVID-19 (remember it is SARS-CoV-2), and what we do know is concerning, if not terrifying. SARS affects the respiratory system causing severe pneumonia making it nearly impossible to breathe without the help of ventilators. Some doctors have likened it to filling up the lungs with peanut butter or concrete. And those presenting with acute respiratory distress syndrome (ARDS) are the easy ones. Doctors treating COVID-19 patients have also found many patients do not appear to be short of breath and yet there is less and less oxygen being circulated through the body so a kind of slow suffocation occurs. Still, others present with no signs of respiratory distress or low oxygen levels and will suddenly develop full-blown ARDS and die within hours to days. Random presentation of symptoms is difficult to recognize and puts everyone at even higher risk.
The problem with COVID-19 is the measures that eradicated both SARS and MERS don’t work with COVID-19 because its incubation period is anywhere from one day to 12 days and people are infectious long before any symptoms develop. It is now believed asymptomatic (infected people without symptoms) transmission is occurring and resulting in clusters of COVID-19 illness within communities.
The past couple of months have been tough. Thousands and thousands have lost their jobs, businesses have closed, and life as we knew it is no longer. And yet, aggressive suppression of the virus is still our best option, meaning continued isolation of the sick, social distancing, and closing those businesses not essential to meeting our basic needs. Aggressive suppression buys us time to develop a vaccine (which is a type of herd immunity), and develop new treatments. Impatience and calling for herd immunity without understanding the consequences will result in millions more dying. How many of your family, friends, neighbors, and co-workers are you willing to watch die…..?
Resources: CDC, MIT Technology Review