Covid-19: What you need to know today
Mumbai, ravaged by the coronavirus disease pandemic – 290,914 cases and 11,076 deaths till Sunday evening – has seen a 50-85% reduction in incidence of dengue, H1N1 flu, gastroenteritis and leptospirosis, infective diseases that plague the city during and after the monsoon every year, according to HT’s Mumbai health reporters. October is one of the unkindest months in India’s commercial capital, with the heat and humidity combining to make it very uncomfortable, and also extremely conducive to the propagation of the diseases named above, but this time, the city seems to have been spared, courtesy an unlikely savior – Covid-19. The safety protocols associated with the coronavirus disease – frequent hand washing, wearing masks, being socially distant, eating mostly home-cooked food – and the restrictions the pandemic has forced upon us, in terms of travelling (it’s so easy to catch a flu on a flight) or even moving about appear to have helped. Mumbai won’t be the first region to have caught a lucky break from Covid-19, though.
In July, The Wall Street Journal reported that the southern hemisphere – it usually sees more cases in its winter, which begins around late May and early June – was seeing very few cases of influenza. The report pointed to a 95% drop in flu cases in Chile (at the time the report was written), and a 64% decline in Argentina. In Australia (a country that usually bears the brunt of influenza), a two-week period in the second half of June, saw a 99% drop in flu cases. The report quoted experts who attributed the fall to restrictions that were in place to halt or slow the spread of Covid-19. The near-absence of international travel was cited by some of them as one of the main reasons behind the steep fall in influenza cases, but they also mentioned other newly acquired human habits (hand washing, wearing masks) as contributory factors.
In mid-December, Nature reported a similar situation in the northern hemisphere where “the levels of many common seasonal infections remain extremely low.” The report, which acknowledged that the southern hemisphere almost completely evaded seasonal influenza added: “The patchwork of responses intended to fight the pandemic – from temporary lockdowns to mask wearing, social distancing, enhanced personal hygiene and reduced travel – has had a huge impact on other common respiratory illnesses too.” The same report, using data from the FluNet global influenza surveillance system, showed that even the last flu season (2019-20) was cut short by measures announced to fight Covid-19, with the number of cases tapering off in April. Interestingly, the Nature report adds that the viruses that cause the common cold, rhinoviruses, do not seem to be affected greatly – mask or no mask, and whether you wash your hands or not, you are going to catch that cold.
India typically sees a surge in influenza cases around this time of the year. This year, anecdotal evidence from Delhi, and the data from Mumbai suggest there have not been as many cases as there usually are. But the data from Mumbai is also revealing – it shows that basic hygiene is among the best prophylactics for a variety of infective diseases.
Post script: A paper published on the pre-print server medRxiv by researchers from Yale (including Akiko Iwasaki) shows that the timing of a body’s immune response is perhaps more important than its magnitude when it comes to fighting off Covid-19. According to the paper, which is based on a study of 209 Covid-19 patients (ranging from asymptomatic to those with severe infections), those whose immune systems produced neutralising antibodies within 14 days of turning symptomatic had a much higher chance of recovery than those whose systems produced these antibodies after 14 days (even if they did more). As Iwasaki pointed out on Twitter, this means that any antibody treatment (such as the use of monoclonal antibodies) will therefore have to be used early in the treatment cycle to be successful.