I’m sure most of you must be under the notion that if one member of the family contracts COVID-19, the others will too. But this is just a myth. According to the Indian Institute of Public Health, Gandhinagar, 80-90% of the people living in the same house as that of a COVID-19 patient do not get infected with the coronavirus. The institute’s director, Dileep Mavalankar, says that such family members seem to have developed some sort of resistance or immunity against the coronavirus.
Mavalankar says, “The assumption that everyone is susceptible to coronavirus may not be true. It is said that a few minutes of exposure to the coronavirus outside will get us infected. If that is the case, then why not everybody in the same household is getting COVID-19 after one member gets infected? There are some families where all members are infected, but they’re not in majority. There are even homes where one person has died of COVID-19, but no other member is infected.”
According to 13 papers published globally on the topic of household COVID-19 transmission, nearly 80-90% of members of a family do not get infected even when one member gets infected. This shows that the household secondary attack rate (SAR) or the rate of transmission of the coronavirus in a household is just 10-15%. Only three out of 13 papers have reported a SAR of 30-50%. This study was recently published in the Quarterly Journal of Medicine, Oxford, UK. It is co-authored by Dr. Mavalankar along with faculty members Komal Shah and Deepak Saxena.
One of these 13 papers has been published by ICMR and it claims that only 8% household transmission of the coronavirus has been recorded. Dr. Mavalankar says, “Some studies have gone into the details of transmission between husband and wife or vice versa, which is shown in the range of 45-60%. But even this is between 15-20%.
He further added to his statement, “Different people have different immunity to the virus. Within a household, we do not follow social distancing rules or use masks. Between the appearance of the symptom and diagnosis, there is a gap of three to five days, which means all the family members are exposed to the virus. But still, not all get it.”
According to researchers, the zero surveillance study to measure antibodies against COVID-19 in the population would be helpful to find out exactly how many people have been infected. As per the theory of ‘immunological black hole’ proposed by Karl Friston, a neuroscientist at University College of London, half of the population is not susceptible to coronavirus. Based on the data he collected, Friston claims that 50% of the European population is not susceptible to the viral infection.
Dr. Mavalankar says, “One of the first reasons for this is many people are limited to their homes and are not going out much, while some people already have some immunity due to some other infection or cross-immunity, and some are susceptible but develop a mild infection that cannot be transmitted to others.”
This can further be proved by the seroprevalence that reached 23% in Delhi and 50% in Dharavi, Mumbai. It shows that the infection must be so mild that it did not pass to others. So, in these areas, we can say that herd immunity is evolving. Recently, ICMR changed the COVID-19 testing guidelines, and hence, only symptomatic family members are getting tested.
Only further research can clarify whether all members in a household are susceptible to COVID-19 if one gets infected or not. However, you must try and isolate yourself from any family member who tests positive for COVID-19. Only social distancing and safe hygiene practices can protect you from the deadly coronavirus.