Like many respiratory viruses, SARS-CoV-2 could exhibit seasonal patterns, according to Dr. Anthony Fauci, Director of the U.S. National Institute of Allergy and Infectious Diseases (NIAID).
The novel coronavirus continues its global spread, now impacting over 170 countries and more than 490,000 people worldwide, with over 22,000 fatalities. While most cases remain in the Northern Hemisphere, infections are rising in the Southern Hemisphere as winter approaches. This trend, says Dr. Fauci, indicates that SARS-CoV-2 may recur in seasonal cycles.
“If countries in the Southern Hemisphere experience a significant outbreak, it will be critical for us to prepare for a second cycle,” Dr. Fauci cautioned during a White House press briefing on Wednesday.
Seasonality in SARS-CoV-2 wouldn't be unexpected. Many infectious diseases follow predictable seasonal rhythms—cholera thrives in hot, humid summers, while influenza peaks in cold, dry winters. SARS-CoV-2 shares traits with flu viruses, prompting questions about winter severity.
Influenza viruses are encased in a lipid envelope rich in cholesterol, which destabilizes in the host's respiratory tract to enable infection and replication. However, this envelope is vulnerable to heat and ultraviolet rays from sunlight, limiting survival in warm conditions unless inside a host.
High humidity also hampers transmission by weighing down respiratory droplets. Additionally, low humidity dries nasal passages, increasing vulnerability, as shown in mouse studies.
Though not identical to influenza, SARS-CoV-2's properties suggest similar seasonal behavior. Initial outbreaks in immunologically naïve populations can be devastating, akin to wildfires in dry forests, as Columbia University epidemiologist Micaela Martinez explains.
Subsequent waves will affect partly immune populations, becoming less intense but still dangerous. This underscores the urgent need for effective vaccines and treatments, Dr. Fauci emphasized.
Major vaccine trials are underway in China and the U.S., with potential market availability in 12-18 months if successful. Other efforts include antimalarials like chloroquine and hydroxychloroquine.
Source: AFP
