Corona Daily 184: What Happened to Flu-20?

This is strange and unusual.

Usually, about twice a year, most members of my gym start coughing in the same month. Some complain of a sore throat, runny nose, sinusitis and headache, occasional fever. The symptoms last for a good two to four weeks. Cough and common cold have become more tenacious in the last decade. The general public, less fit than my gym colleagues, also experience ‘the flu’ annually. Because we are Indians, we never take flu vaccines. We suffer, carry on with our life, infecting one another, until the season is over.

I don’t want to jinx it, but I have not had any of these symptoms in the last ten months. 2020 was probably the first flu-less year in my life. And I find this is true for many of my friends, relatives and neighbours. My octogenarian parents are also healthier during the pandemic. Where is the flu-virus 2020-21 hiding?

I will move from empirical evidence, to official statistics. In the flu season 2019-20, USA had 22 million influenza cases, 210,000 hospitalizations and 12,000 deaths. This year, almost nothing. In countries where influenza is tracked, numbers are down by 99.5%. The American CDC map, always red in February, is completely green this year. It’s not that Americans or Europeans have not tested for influenza. Almost all tests have been negative.

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As we well know, the flu virus and Covid-19 are both respiratory and spread in a similar manner. Tiny particles of mucus or saliva spew out when people cough, sneeze, talk or breathe. Handshaking, hugging, being together in a room can enable transmission.

Evidently, the containment measures we take for the coronavirus; masks, hand hygiene and social distancing have helped barricade the flu virus as well. Equally important is our reduced travel, closed offices (and gyms), shut schools and day cares. Children are great transmitters of flu.  

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There is another interesting theory.

It talks about viral interference, the phenomenon of viruses affecting each other. It was noticed in the eighteenth century by Edward Jenner, the English developer of the smallpox vaccine. He would inoculate people with a mild cowpox virus. But when a patient had herpes or another infection, the smallpox vaccine didn’t work. It was almost as if the immune system wouldn’t allow two infections at once.

In September 2009, the H1N1 swine flu had landed in Portugal, Spain and the UK. France prepared for the epidemic. Indeed, the number of cases with respiratory symptoms soon went up. But the infected people didn’t seem to have H1N1. It so happened that France already had rhinovirus, which causes colds. The French population was infected with that virus, and the common cold virus deflected the swine flu. Many studies have been conducted and papers written. They find that people rarely have two viruses at the same time.

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While we are happy about the current low profile of the flu virus, researchers and vaccine developers are worried. The flu virus mutates every year, and new vaccines are developed to fight new mutations. More than 100 countries conduct year-round surveillance by testing thousands of flu virus samples. WHO analyses the data in five centers located in the USA, UK, Australia, Japan and China.

In February, WHO representatives, scientists, academicians review the surveillance results, make predictions for the flu virus next season, and recommend the composition of the flu vaccine. (In September, a similar exercise is done for countries in the southern hemisphere). It takes six months to develop and manufacture the new flu vaccines. Americans are usually advised to take them in October.

The flu’s absence is unsettling for the researchers. They have been starved of data crucial for forecasting and developing vaccines. They are not sure when, how, and in what form the flu will return.

Ravi