By Hagop Kantarjian, M.D.
Nonresident Fellow in Health Policy, Baker Institute
Andrew DiNardo
Infection disease specialist
The Covid-19 pandemic continues to spread its devastation, causing the death of thousands, decimating world economies, and destroying familiar societal fabrics. This should not come as a surprise. The U.S. and the world are still in the early-mid phases of the pandemic, during which the prevalence (total number of infected people) increases by 33% daily, which means it doubles every three days ( actually 2.3 x increase). Since the last Baker blog update on Covid-19 (March 24, 2020; six days ago), the number of cases in the U.S. has increased from 50,000 to 165,000 (3,200 deaths).
Possible Covid-19 surge in Houston around April 10-17?
Houston and other cities in Texas have so far fared better than cities on the East and West coast. Texas’ metropolitan areas are more spread out and less densely populated than, say, those in New York. Houston has a warm and humid climate (may limit the spread of Covid-19), which we may be for once thankful for. But based on updated data (discussed later), Houston must continue to prepare seriously for a Covid-19 surge in mid-April, possibly related to the Houston Rodeo, which was cut short on March 11,2020 (attracted 200,000 people), and/or a possible influx of Covid-19 positive cases from Louisiana. We hope this will not be a source of a surge in Houston, but if it is, it may happen around April 10-17.
How and where the virus has spread
The first cases of Covid-19 were reported in China on November 17, 2019. The disease abated there in early March, after severe social restrictions and widespread Covid-19 screening, isolation and prevention. As of March 30, 2020, of about 1.3 billion citizens, about 82,000 were infected (infection rate less than 0.01%), and 3,300 died (mortality rate 4%). Some experts have questioned these numbers, suspecting the number of deaths related to Covid-19 to exceed 10,000. They also criticized China’s delays in accurately reporting on the Covid-19 outbreak and its lack of transparency.
Some countries took the threat of Covid-19 seriously, having experienced previous regional epidemics like Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS). They developed early Covid-19 testing and wide screening, and implemented strict social isolation/distancing. They fared well so far. These include South Korea (population 51 million, infections 9,800 = 0.02%, deaths 162 = 1.6%); Australia (population 25.5 million, infections 4,600 = 0.01%, deaths 15 = 0.4%); Singapore, Hong Kong, Japan, Thailand and others. Countries that ignored the Covid-19 threat early on fared less well: Spain (population 47 million, infections 95,000 = 0.2%, deaths 8,200 = 8.6%); and Italy (population 60.5 million, infections 102,000 = 0.17%, deaths 11,600 = 11.3%). Studies have shown that, in such outbreaks, a delay of control measures by one week can triple the epidemic size and prolong it by one month.
The Covid-19 pandemic effect in the U.S. is unfolding and changing daily. The U.S. may not have considered Covid-19 as serious at the beginning, and had delays in wide Covid-19 testing (because of issues in developing the test) and in social restrictions. Of 330 million American, 165,000+ are now infected (0.05%), and 3,200 have died (mortality 1.9%).
Some updated information about Covid-19
The basic information about Covid-19 is detailed in previous blogs. It is highly contagious. Seasonal influenza transmits from 1 person to 1.2; Covid-19 transmits from 1 person to 6-7 without precautions, and to 2-3 with precautions. A person infected with Covid-19 can have no symptoms for three to seven days, and many have no or mild symptoms. Infectivity is highest around days five to six from exposure, and 80% of Covid-19 spread is caused by the 10-20% of infected people who have minimal or no symptoms (better referred to as “subclinical” cases), because of lack of widespread Covid-19 testing. This explains why the Covid-19 spread is so difficult to control, and why the current CDC criteria for Covid-19 testing (cough and shortness of breath, fever, and known exposure) are not good enough. The clinical disease and infectivity last another one to two weeks. But there are outliers with clinical disease lasting three to four weeks, which explains why we may have to implement long city lockdowns. Here, we may learn from our forebears who, having little medical knowledge about the cause and behavior of epidemics (plague, smallpox, cholera, typhoid), implemented isolation in the form of “quarantaine” (started with the bubonic plague of the 14th century), a French word that refers to 40 days. We hope Covid-19 will not require six-week lockdowns, and we can be guided to remove restrictions by whether the daily prevalence flattens.
We do not know if Covid-19 will recur in several waves, and if a second wave will be with a more virulent virus (like with the Spanish influenza) or a less virulent one (as is more common with viruses). Several research groups have now reported that Covid-19 is transmitted less in warmer weather and is seasonal (subsiding in warmer weather and recurring in the cold season). The 1918-1920 pandemic Spanish flu developed in three waves over two years, infected a third of the world population (500 million of 1.5 billion) and caused the death of 50 million people (range 20-100 million; estimated mortality rate 10% over the three waves; 3% of the total world population then). Most of the deaths were in the second wave. But there were no vaccines or antibiotics then. Covid-19 has a lower mortality rate. Based on coronavirus studies in Macaque monkeys, Covid-19 infection may produce immunity lasting for up to one year and may or may not recur. But even if it does, based on current progress, effective and safe vaccines and new drugs to treat the virus may be available by then. So the long-term health-care impact of the Covid-19 pandemic will hopefully be much less severe than that of the 1918-1920 Spanish influenza. However, the long-term economic impact may be worse because of the globalization and interconnection of world economies (discussed in the Baker blog of March 24, 2020).
As of March 31, 2020, the total number of Covid-19 infected people is about 800,000 (likely to exceed 1 million by the end of the week) and the number of deaths 40,000 (mortality 5%). This is expected to continue for another two to three months, following China’s experience. The early Covid-19 infection picture shows an increase in the number of infections by 33% daily. This is unless wide Covid-19 testing and severe social restrictions are implemented.
Why the difference in mortality rates in different geographies?
Different geographies are reporting somewhat different mortality rates: 5% worldwide; 1-2% or less in some countries; more than 5% in others. This may relate to different factors: early and widespread testing, social distancing, weather conditions, medical capacities and others. For example, widespread Covid-19 testing increases the denominator of people tested to include subclinical and milder cases, resulting in a lower mortality rate. Limited screening (for example by the CDC criteria) would include the more symptomatic and severe cases, resulting in a higher mortality rate estimate.
Efforts to contain Covid-19 in the U.S.
The status and control of Covid-19 in the U.S. varies by different regions. The first case in the U.S. was reported on January 16, 2020. With widespread Covid-19 testing, case tracing and isolation of infected people, and social restrictions and distancing, the pandemic should start tapering by late May 2020. Infection and mortality rates in the U.S. and the world may depend on factors inherent to different geographies and cultures: cultural norms and traditions related to the amount of social contact; human densities; extent of reliance on mass transit, public transportations and subways; local weather (warm and humid weather better); tourism influx; mass gatherings. This is why some U.S. cities became early Covid-19 epicenters: New York, Seattle, San Francisco and Chicago. These cities are in the midst of the Covid-19 massive surge, with overwhelmed medical infrastructures (hospital beds, intensive care unit beds, respirators, health care workers). Activation of the Defense Production Act may help secure supplies (ventilators, testing kits, personal protective equipment).
Why did New Orleans and Louisiana become the most recent and fastest growing Covid-19 epicenter? A number of factors may have contributed to this: human density, tourism, a seaport connection to the world, warm cultural and family relations, poverty and overcrowding. Also, importantly, New Orleans lives on tourism and good times, and the city just concluded on February 25 a week of massive Mardi Gras festivities that attracted 1.4 million people. This may have caused the current Covid-19 surge, about four weeks later. As stated earlier, a similar surge may happen in Houston four weeks after the rodeo.
Looking ahead and modeling expectations of Covid-19 outcome
What should we expect the overall effect of Covid-19 to be in the U.S.? The CDC has produced different predictive models. But these assume wide ranges of infection rates (20% to 60%) and of mortality rates (0.5% to 4%), and produce vastly different numbers. Based on the Diamond Princess Boat cruise Covid-19 closed box experience (3,300 crew members and passengers, 712 infected, 10 deaths), the infection rate may be as high as 20% and mortality rate 1.5%. But this model is geographically dense and restricted, similar to an epicenter, and we have noted that so far, the current infection rates in different countries are less than 1-5%. So we hope the mortality figures will be lower. If we extrapolate the Princess Boat data to the U.S., the first Covid-19 wave may infect 69 million Americans and cause the death of almost a million. But if we use an infection rate of 1% to 5%, as it is in many other countries, and a 2% mortality rate, then 3 to 16 million may be infected and between 60,000 and 320,000 Americans may die (with immediate and widespread Covid-19 testing and severe social restrictions).
Particular concerns about Houston and the Texas Medical Center
Houston is home to the Texas Medical Center, the largest medical complex in the world: more than 10 million patients annually; 160,000 patient visits daily; 56 institutions; 21 hospitals; and 106,000 employees, most of whom have daily and frequent contact with patients. These medical facilities care for patients highly vulnerable to Covid-19. The CDC criteria for testing will not protect the health care workers or their patients from the spread of Covid-19. Health care workers in contact with patients should be tested under more stringent criteria (minor symptoms and/or periodically) than the CDC criteria, in order to protect them, their patients, their families and social circles, and the Texas Medical Center as a whole.
Covid-19 testing through nasal wash and blood samples is becoming more widely available, but still unfortunately two months later than we could have.Abbott Laboratories received an FDA approval to launch a 5-15 minute test using an easily portable medical device (plans to supply 50,000 tests daily starting April 1, 2020), and approval for a larger system, m2000 Real Time, that can test up to 1 million samples a week.
Summary
Based on the updated data about Covid-19, Houston must prepare seriously for a Covid-19 surge in mid-April, possibly related to the Houston Rodeo mass crowding and/or an influx of Covid-19 positive cases from Louisiana. The next month will clarify better how Covid-19 will affect our lives and economies.
About the authors
Hagop Kantarjian, M.D., is a medical oncologist and a nonresident in health policy fellow at the Baker Institute. His opinions do not reflect those of his institution affiliation
Andrew DiNardo is an infection disease specialist. His opinions do not reflect those of his institution affiliation.