What is
COVID-19?

COVID-19 (Coronavirus Disease 2019) is primarily a respiratory tract infection caused by a newly discovered coronavirus species called SARS-CoV-2 (Severe Acute Respiratory Syndrome 2), likely to have originated from a zoonotic virus (bats, Malayan Pangolins).

COVID-19 is a very diverse illness which can range from asymptomatic to a severe presentation, sometimes involving hospitalization.

The disease was first documented in Wuhan, China, within the Hubei Province. It was first isolated from stall workers at the South China Seafood Market, where amongst other things, wild animals were sold. The outbreak commenced in China most likely during mid-November of 2019.

Interpersonal transmission is thought to occur by close contact, likely via respiratory droplets. However, it is uncertain when in the course of infection, a person truly becomes contagious to others. There is a distinct possibility that the virus may be transmitted even in the asymptomatic period, as studies have shown that it has the ability to replicate and be present at very high viral loads in the upper respiratory tract during this time.

Transmission of the virus from surfaces to people has also been implied. Studies have shown that the virus can survive for 72 hours on plastics (but less than 0.1% remains at the end of this period and unlikely to be infective), 48 hours on stainless steel, 24 hours on cardboard, and 4 hours on copper. In general, it is less likely to contract the illness from contact with surfaces than when exposed to others.

SARS-CoV-2 has been detected in the fecal material and gastrointestinal tissues of documented COVID-19 patients, however, it is not known if it is infectious in this state. A recent study was able to show that infectious SARS-CoV-2 was isolated from the urine, and therefore, urine may be a source of transmission. It is not known if SARS-CoV-2 can be spread from untreated sewage material, unlike the SARS-CoV outbreak in 2003. It has not been detected in drinking water. We are currently unaware if seasonal temperature changes affect the viability of the virus.

More information has surfaced to support the theory of airborne transmission. In one Chinese hospital-based study, SARS-CoV-2 was found readily in the air and object surfaces in the ICU and general ward (non-ICU rooms). Distance of travel of the virus may be as far as 4 meters (12 ft). Air samples: 35% positive for SARS-CoV-2 in the ICU setting, compared to 12.5% in the general ward room. The virus was found on floor samples (70%), soles of shoes (50%), computer mice, trash cans, patient handrails, patient masks, air outlets near the door of the room, and the doctor’s office. The virus was detected on the floor of the pharmacy (100%), but 0% in the pharmacy air. This suggests that floor traffic can spread the virus over long distances. Interestingly, face shields of health-care workers had 0%, while their sleeves, gloves, and soles of their shoes had significant amounts, reinforcing the contamination via surface theory.

Studies have shown that COVID-19 patients became infectious (starting to shed virus) approximately 2.3 days before experiencing symptoms, with peak infectiousness (highest viral load) 0.7 days prior to symptom onset. Infectiousness (viral load) tapers quickly within 7-8 days after symptom onset, with continuation of detectable virus at very low quantities up to a median of 21 days, (one subsequent study reported 31 days), though likely not enough to propagate infection.

There were no differences in viral loads seen between age, sex, or severity of disease, suggesting that no matter how sick one became, everyone had similar levels of virus. 30-40% of cases are transmitted during the pre-symptomatic period (before symptom onset), therefore solidifying the significance of social distancing as a prevention measure.