Burn virus, burn: Can COVID-19 burn itself out in summer?

By Maggie Chen, Alexandria Lee, Trang Truong, and Kimmy Ye

With summer in full swing, there are many questions revolving around how warmer weather affects COVID-19. As states return to normal operations and people start to venture outside the house more often, we should keep several things in mind to have a safe Independence Day weekend and reduce the chances of transmission, and as we prepare for the second wave of outbreak.

Warm weather and choice of countless outdoor activities have made going out and meeting friends more tempting. With the uptick of interactions, enforcement of social distancing and wearing masks have become more challenging. Many states that reopened as early as April, have transitioned into allowing businesses like bars and restaurants to serve and operate even inside their facilities. Now several phases into reopening and reintegration, the U.S. has seen an alarming rise in the number of COVID-19 cases by nearly 50% and set a new daily high of over 55,000 incident COVID-19 infections by the end of June, led by the very states that reopened earliest. Bars and restaurants previously allowed to reopen have been closed again across states including Florida, Arizona, Texas, and California.


Figure 1. The trend of confirmed new cases in the 10 most-affected countries.

Human

Weather and humidity can drastically affect our respiratory health. The respiratory tract tends to be more vulnerable in the winter. Human airways serve to keep the air warm and moist to make it easier to breathe. Since the winter air tends to be drier and colder, there is more stress placed on the human respiratory system. Weather is one of the factors that contribute to the seasonality of common flu. However, it is worth noting that the 1918 pandemic flu did not follow a seasonal pattern, and such phenomenon is called a Herald wave. The 1918 pandemic occurred in the summer and it carried on for more than a year.

While remaining in quarantine greatly reduces the risk of COVID-19 transmission from a human behavioral standpoint, the key to a healthy quarantine is ventilation. There are other pathogens (normally present before COVID-19 times) to take into consideration when staying indoors without sufficient ventilation and air exchange. Indoor air (AC, heating system) can be an important vehicle for a variety of human pathogens transmitted.

Virology

A common question is whether COVID-19 can be classified as a seasonal disease. Some research has been conducted to try and characterize the COVID-19 virus in relation to weather conditions. While it is true that sunlight and UV rays can decrease the viability of the COVID-19 virus on surfaces, this does not mean that going outside into the sun will help people who already have the virus inside their system. The World Health Organization (WHO) has also warned that a person can become infected with COVID-19 regardless of temperature conditions, as seen in countries with normally very hot weather reporting cases. The virus can also stay active at colder temperatures, including at temperatures found in our upper respiratory tract.

It is important to note that many of the findings related to the COVID-19 virus are discovered in isolated laboratory settings that may not be representative of the conditions of common public spaces such as grocery stores and parks. Therefore, it is best to exercise caution when venturing outside as new characteristics of the COVID-19 virus continue to be elucidated.

Figure 2. Michigan state public health experts Dr. Matthew Sims (Beaumont Health director of infectious disease research), Dr. Dennis Cunningham (McLaren Health Care medical director for infection prevention), Dr. Mimi Emig (retired infectious disease specialist with Spectrum Health), and Dr. Nasir Husain (Henry Ford Macomb medical director for infection prevention) shared their assessment of risk for various activities involving social interactions.


With the Fourth of July weekend coming up, many are wondering how COVID-19 will affect celebrations. There are ways to safely celebrate the Fourth without putting yourself at more risk for infection. Experts featured on NPR, such as Dr. Aaron Carroll from Indiana University, are asking that people keep three things in mind as we head into the weekend:

  1. Being outdoors is better than celebrating indoors. Social distancing measures are easier to implement outdoors.

  2. Wearing a mask at all times except for eating and drinking is always the rule of thumb.

  3. Smaller celebrations are much safer than larger, more crowded gatherings.

Other tips include avoiding the sharing of food and drinks, establishing ground rules on social distancing and other safety measures with guests before their arrival, having designated servers for specific dishes to avoid multiple guests handling the same utensil, and setting chairs 6 feet apart so guests can social distance comfortably. As Paula Cannon, a virology professor at the University of Southern California’s School of Medicine, acknowledges: though it may be unrealistic to prohibit all forms of celebration for the Fourth of July, it does not mean that we are unable to celebrate responsibly.

Final words

Historically, the SARS and MERS outbreaks were relatively well controlled due to their virology and, most importantly, strict quarantine and wide testing. Ultimately, weather condition was not associated with controlling those outbreaks. Additional considerations that may exacerbate the transmission of COVID-19 are extreme weather and natural disasters, both of which create breeding grounds for outbreaks globally (e.g. earthquake in Mexico, flood in India).

Experts are currently warning not to count on COVID-19 going away any time soon. In fact, the fight against the pandemic may get tougher in the near future. One complicating factor is the common flu, which follows seasonality patterns. When the second wave of infections hit for COVID-19, experts suggest it will be difficult to distinguish between patients infected with the flu and those afflicted with COVID-19 considering the similar initial symptoms between the two such as a cough, sore throat, headaches, and fatigue.


Results from ongoing research and the current understanding of COVID-19 are constantly changing and growing. This post contains information that was last updated on July 1, 2020.

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