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"COVID-19 Winter” Starts in June in the Southern Hemisphere: Will There Be Treatments and Prophylaxis?

Posted on Sunday, Mar 22, 2020

Authors: Kristen Kent*M.Phil, Nellie Darling MS, Daniel Lucey MD, MPH, FIDSA
Georgetown University School of Medicine, Washington, DC. 
*Corresponding author:
Will the COVID-19 pandemic be over by this summer in the Northern Hemisphere? Too many of us in the Northern Hemisphere forget that June-September is winter in the Southern Hemisphere. Given no human immunity to this novel coronavirus, even if transmission slows during the approaching Northern Hemisphere summer, it will likely increase in the simultaneous Southern Hemisphere winter.  Fortunately, before June 2020 results from randomized controlled trials in China, and likely Europe, will give urgently needed results as to whether any drugs are effective treatments for ill patients, and whether any are effective prophylaxis to protect persons from getting infected.  

COVID-19 has already been documented in 18 countries in the Southern Hemisphere (Table 1).  The recognized ongoing spread in Australia, Brazil, Indonesia, and South Africa suggests that there is more widespread transmission in nations in the Southern Hemisphere than documented by laboratory-confirmed testing. Thus, we should not expect to see a resolution in COVID-19 transmission rates in the world simply because of warmer weather in the Northern Hemisphere.

In fact, circulation of the SARS-CoV-2 that causes the disease COVID-19, Is likely to continue year-round. This transmission pattern diverges from that of SARS-CoV-1, the virus that caused the disease SARS in 2002-2003. Thanks to a massive effort coordinated by the World Health Organization (WHO), SARS did not spread in the Southern Hemisphere before it was stopped July, 2003.

Instead, COVID-19 is most likely to follow the pattern of pandemic influenza pdmH1N1 in 2009. Given the lack of human immunity, like now with Covid-19, pdmH1N1 influenza was transmitted through the June-September summer in the Northern Hemisphere, and was transmitted through the simultaneous winter in the Southern Hemisphere.  Sustained transmission of this novel influenza virus in the Northern Hemisphere did decrease, but did not stop, in July and August 2009 (1).  Likewise, we should expect to see year-round transmission of the novel coronavirus SARS-CoV-2, given the absence of any pre-existing immunity in humans.  

Many clinical trials are currently underway in an effort to find treatments and prophylaxis (prevention) options for COVID-19. One such trial is with Remdesivir, a nucleotide analog that failed in clinical trials for the treatment of Ebola but has in vitro activity against coronaviruses.   One very recent clinical trial in the USA is investigating Remdesivir in a multi-center, double-blind study sponsored by NIAID/NIH (2). China initiated one or more randomized controlled trials (RCT) of Remdesivir during their pan-epidemic in Wuhan, Hubei province, and across China. Results from the first RCT of Remdesivir in China are anticipated by late April.

One example of a clinical trial for prophylaxis against infection is with an anti-malarial, chloroquine. This double-blind trial will be coordinated by the University of Oxford in the UK (3). The study is recruiting healthcare workers across 50 sites who will be randomized to either chloroquine or placebo group. Treatment will continue for 3 months or until a subject contracts COVID-19. This trial may not be completed for as long as 5 months, but interim analyses may be reported if clear efficacy or futility are seen.

For the coming “COVID-19 Winter” in the Southern Hemisphere, as well as the “COVID-19 Summer” in the Northern Hemisphere, any effective treatment or prophylaxis proven through randomized controlled trials will be a true “game-changer” based on scientific evidence and nothing less.   

  1. The 2009 H1N1 Pandemic: Summary Highlights, April 2009-April 2010. CDC. Updated June 16 2010.
  2. Adaptive COVID-19 treatment trial (February 21, 2020).
  3. Chloroquine prevention of Coronavirus disease (COVID-19) in the healthcare setting (COPCOV) (March 11, 2020).
Table 1. Southern Hemisphere Nations with Cases and Deaths. (Data extracted and tabulated from WHO reports though 19 March 2020).