Respiratory transmission: SARS-CoV-2 is transmitted from person-to-person while in close contact that is within 1 meter of distance. Infection occurs through aerosol or droplets carrying the virus either by: (i) Inhalation, or (ii) inoculation to mucosal surface of nose, mouth or conjunctiva; or (iii) by touching the mucosa by hand contaminated with virus containing respiratory droplet or fomites. Transmission mostly occurs from a symptomatic person through sneezing, coughing and talking when the infected droplets are produced and get dispersed in the air.

Asymptomatic person transmission: Trans mission from asymptomatic COVID-19 positive individuals is also common as the virus shedding occurs through nasal and pharyngeal mucosa. The infected particles from nose and oral cavity can infect the nearby person. This is also common as it may take 2 14 days to develop symptoms after acquiring the virus (incubation period) and also could be due to many infected individuals have mild symptoms which go unnoticed. During this period, virus replication and shedding occurs which makes the person a potential source of infection but as the person appears otherwise normal, they are not usually considered as an overt source of infection. So, essentially asymptomatic persons are silent transmitter of the infection.

The average size of the droplet particle is 5–10 µm which usually gets deposited within 1 meter area, therefore, transmission usually occurs due to close contact with the infected person within this distance.

Aerosol transmission: Lower size of respiratory particle carrying the virus may remain suspended in the air for a long-time and can get dispersed to a longer distance (>1 meter) possessing the risk of airborne transmission. In general, the risk through air-borne trans mission is less excepting crowded places where the possibility cannot be ruled out. This is based on the finding of less concentration of viral RNA from aerosols of various isolation wards, ventilated patients and public places. The chance of aerosol transmission is more in crowded places and closed and poorly ventilated rooms. The risk is higher when the process of aerosolization is involved such as endotracheal intubation, bronchoscopic procedure, nebulization or cardiopulmonary resuscitation, etc.

Fomite transmission: Indirect transmission through fomites is also a possible source of transmission. Viral RNA has been detected from environmental surfaces and fomites from rooms occupied by SARS-CoV-2 infected symptomatic or asymptomatic individuals. However, there is no evidence regarding the infectivity and transmissibility through fomites.

Feco-oral transmission: The potential of feco oral route of transmission is considered due to the expression of ACE-2 and TMPRESS2 in the gastrointestinal tract epithelium and thereby infection and viral replication in GI tract. SARS-CoV-2 RNA has been detected in stool sample for up to 42 days and usually positive in stool for prolonged period than in the nasopharyngeal swab. Several studies have shown stool RT-PCR positivity in about 30% of COVID-19 positive cases. Viability of virus has been shown by successful culture of virus from stool sample in Vero cells and detection of viral RNA from toilet surface and door handle of room of a patient whose stool sample was RT-PCR positive. Sewage aerosol had caused an outbreak of SARS-CoV in an apartment in Hong Kong in 2003. Considering the evidences regarding presence and viability of SARS-CoV-2 virus in stool sample, possibility of spread of SARS-CoV-2 virus through similar mechanism also exist.

The potentiality of vertical and sexual route of transmission of SARS-CoV-2 has also been shown, however, so far no convincing evidence have come up to consider these routes as the mode of transmission.

Vertical transmission: COVID-19 positivity has been demonstrated in neonate born to COVID-19 positive mothers. Babies have been found to be positive for COVID-19 IgM anti bodies in most of the studies. However, there is no consensus regarding the vertical trans mission as many other studies have shown lack of such evidence. Preterm delivery and miscarriage have been reported in COVID-19 positive pregnant ladies. However, so far there is no evidence of fetal malformation due to COVID-19 infection.

Sexual transmission: Some studies have shown the SARS-CoV-2 RNA detection in semen of COVID-19 positive males particularly during the acute phase of infection. However, there is no concrete proof of sexual route of transmission though the viral RNA has been detected in semen.

اخر الاخبار

اخبار العتبة العباسية المقدسة

موكب العتبتين المقدستين يحيي ذكرى استشهاد الإمام الهادي (عليه السلام) في سامراء

العتبة العسكرية المقدسة تكرّم وفد العتبة العباسية المقدسة لمشاركته في تقديم الخدمات للزائرين

العتبة العباسية المقدسة تختتم مشاركتها في تقديم الخدمات لزائري مرقد الإمامين العسكريين (عليهما السلام)

وفد متحف الكفيل يطلع على الفنون التراثية والحرف الأصيلة في ورش مدينة أصفهان

المزيد

الآخبار الصحية

كنز غذائي على طبقك.. ماذا تفعل السبانخ بجسمك؟

ما لا يتوقعه أحد.. "سر غذائي" في الجبن الدسم

لتحسين الهضم والنوم.. هذا أفضل وقت لتناول العشاء

10 طرق بسيطة وغير مألوفة لحرق المزيد من السعرات يوميا

المزيد

الآخبار التكنلوجية

سابقة بعالم الطيران.. طائرة تقرر الهبوط بنفسها بعد ظرف طارئ

"الإنفلونزا الخارقة" تكتسح دول العالم.. وتثير قلقا كبيرا

مرحلة ما قبل الأعراض.. دواء جديد يستهدف "شرارة" الزهايمر

إزالة ثاني أكسيد الكربون من الغلاف الجوي.. ما دور المحيطات والبحار؟

المزيد

مواضيع ذات صلة

Complications of COVID-19

Clinical Features of SARS-CoV-2 and COVID-19

Papillomaviruses

Arenaviruses

Adenoviruses

Viral Serology: Immune Status Testing

Structure and Function of Hemagglutinin

Structure and Composition of influenza viruses

Filoviruses Diseases

Pathogenesis of SARS-CoV-2 and COVID-19

Viral Serology :General Principles

Virus detection methods: Cell Culture