Study Suggests Pandemic Won't Fade With Warm Weather

By Gene Emery

April 09, 2020

(Reuters Health) - Don't look for COVID-19 to fade away when summer arrives in the northern hemisphere, a group of Chinese researchers has concluded.

A new analysis of infection rates and climate patterns throughout China has found that the novel coronavirus is not deterred by warmer temperatures or longer days and the additional ultraviolet light that comes with it.

"Our study does not support the hypothesis that high temperature and UV radiation can reduce the transmission of COVID-19. It might be premature to count on warmer weather to control COVID-19," said the Chinese team led by Yao Ye of Fudan University in Shanghai.

Seasonal temperature changes are known to influence the ebb and flow of the flu and severe acute respiratory syndrome (SARS). Cold, dry air, for example, has been known to enhance influenza transmission.

The Ye team analyzed patient records and meteorological data from 224 cities in China looking for evidence that the COVID-19 virus was vulnerable to warmer weather.

When they looked at the rate of spread, "We did not find significant associations of relative humidity, maximum temperature and minimum temperature . . . suggesting that ambient temperature has no significant impact on the transmission ability of SARS-CoV-2," the virus responsible for COVID-19, the researchers reported.

They noted that a related coronavirus that causes Middle East respiratory syndrome (MERS) is also unaffected by higher temperatures.

The study appears online in the European Respiratory Journal.

A separate Chinese study published by the journal is illustrating how COVID-19 becomes more severe when a region is unprepared for it, either because doctors are slow to recognize a new threat or the health care system is overwhelmed.

The rate of severe cases was 19.2% in Hubei province, which contains the city of Wuhan, the epicenter of the pandemic. The rate of severe cases was 11.0% outside the province. Mortality rates were 3.48% in Huebi and 0.22% elsewhere, according to data through Jan. 31.

"There were more severe cases and poorer outcomes for COVID-19 patients treated in Hubei, which might be attributed to the prolonged duration of symptom onset to hospitalization in the epicenter," said the team of researchers, led by Wen-hau Liang of Guangzhou Medical University.

"After the surge of cases in January 2020, hospitals in Hubei province were heavily overloaded and managed an overwhelming increase in the number of patients. These shortages could have led to a delay in the diagnosis and treatment of patients, which further contributed to the worsening of overall status upon admission and an increased risk of death," the researchers said.

They also noted that "Significantly longer waiting time was observed among patients in Hubei province, whereas patients with or without Wuhan-related exposure shared similar waiting time outside of Hubei province. Importantly, we have found that the prolonged waiting time, rather than the geographic location or the Wuhan-related exposure history, predicted the clinical prognosis of COVID-19."

The Liang team also saw a different pattern of symptoms inside and outside the province.

Among patients in Hubei, rates were 15% higher for fatigue, 22% higher for productive cough, 31% higher for myalgia or arthralgia and 3.5 times higher for shortness of breath than outside the province. Shortness of breath was initially reported in 36.3% of the Hubei cases versus only 10.2% elsewhere.

The reason for the different pattern is not clear, although in Hubei province, patients were an average of 5 years older and had a 67% higher rate of comorbidity, with rates of 32.9% vs 19.7% outside the province. They were also likely to have more symptoms, more radiologic abnormalities and a longer wait time -- an extra 1.2 days -- between onset of symptoms and admission to the hospital.


"Our findings indicate that the temporary shortage in health capacity in the outbreak epicenter, rather than the transmission history, has resulted in the large number of severe cases or deaths in Hubei province," the Liang team said. "This study highlights the necessity of urgent and vigorous support of healthcare resources and increased public awareness during the early stages of an outbreak of COVID-19 or similar diseases."

Finally, the journal has published a study showing that the lungs of smokers and people with chronic obstructive pulmonary disease (COPD) seem to harbor high levels of an enzyme that may make them more vulnerable to COVID-19.

The enzyme, ACE-2, is what the coronavirus uses to get into the cells lining the lung.

The ACE-2 levels were not as elevated in former smokers.

Those findings "in part may explain the increase risk of severe COVID-19 in these populations" and they "highlight the importance of smoking cessation for these individuals and increased surveillance of these risk subgroups for prevention and rapid diagnosis of this potentially deadly disease," said the group, led by Dr. Janice Leung of the Centre for Heart Lung Innovation at the University of British Columbia.

Health officials in the U.S. have been encouraging people to quit smoking because of the COVID-19 pandemic, speculating that the effects of smoking might make the illness more severe if they become infected.

Smokers and people with COPD are already known to be vulnerable to other lung infections.

SOURCES:;; and The European Respiratory Journal, online April 8, 2020.