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Mathematician warns of coronavirus flare-up as positivity rate stops declining

In Mexico City there was 'a worrying' increase in the last two weeks

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A National Autonomous University (UNAM) mathematician has warned that the national coronavirus positivity rate is no longer declining and that the outbreak could soon worsen.

“At a national level, the positivity rate [the percentage of Covid-19 tests that come back positive] was coming down but now the trend is changing. It went from going down, which is desirable, to stagnating at … 40%. … To consider that the epidemic is controlled, the positivity rate needs to reach 5%,” Arturo Erdely told the newspaper Milenio. 

Mexico’s positivity rate is very high compared to most other countries because testing is mainly targeted at people with serious, coronavirus-like symptoms.

Only about 13,000 people per 1 million residents have been tested for Covid-19 in Mexico compared to about 315,000 in the United States, 84,000 in Brazil and 52,000 in India. Mexico has the fourth highest Covid-19 death toll in the world behind those three countries.

Erdely said the positivity rate in Mexico City, the country’s coronavirus epicenter, has increased from 30% to 34.5% over the past two weeks, an uptick he described as “worrying.”

The positivity rate in Mexico City, April 18 to September 28.
The positivity rate in Mexico City, April 18 to September 28.

“The positivity rate was coming down but now it’s changed and it’s trending upwards. There is variability from one day to the next and from one week to the next but … when the average has been increasing for more than a week you can say that the trend is changing and [the positivity rate] is increasing. While in the case of Mexico City it’s increasing below the national average of 40.3%, it’s been rising and it’s about 34.5%, … which I think is concerning,” he said.

The UNAM academic said the positivity rate is the most important statistic to understand how the pandemic is evolving and the one that the World Health Organization watches most closely. But the federal government has never attributed sufficient importance to it, Erdely claimed.

While the national positivity rate is currently below the level seen in April and May – when it exceeded 50% – it shows that the pandemic has not significantly decreased, he said.

There are signs that new case numbers – which have been on the wane for about two months, according to the federal Health Ministry – could soon begin to rise, Erdely said.

He said that an uptick in case numbers could become even worse if the federal government doesn’t send clear messages about coronavirus mitigation measures such as the use of face masks.

“It’s very complicated. If [economic and social] activity increases, it’s impossible that infections won’t increase. So that [the outbreak] doesn’t get out of control, it’s essential to continue … taking care; social distancing, not going out if you don’t need to, the use of face masks, everything,” Erdely said.

Coronavirus cases and deaths in Mexico reported by day
Coronavirus cases and deaths in Mexico reported by day. milenio

Meanwhile, the Health Ministry reported Tuesday that Mexico’s accumulated case tally had increased to 738,163 with 4,446 new cases registered.

A total of 138,603 cases were reported in the first 29 days of September, 21% fewer than the number registered in the 31 days of August. New case numbers in August declined 12% compared to July, which was the pandemic’s worst month with almost 200,000 cases reported.

But while new case numbers have trended downwards this month and last, several thousand continue to be reported on a daily basis.

Deputy Health Minister Hugo López-Gatell, Mexico’s coronavirus czar, has frequently asserted that the pandemic will be long and warned last week that a new wave of infections could begin in the middle of October, coinciding with the beginning of the flu season.

Mexico also continues to record hundreds of Covid-19 fatalities every day. The Health Ministry reported an additional 560 on Tuesday, lifting the official death toll to 77,163.

The real number of people who have succumbed to the infectious disease in Mexico is almost certainly much higher.

In Mexico City alone, which has officially recorded 12,051 Covid-19 fatalities, deaths from the disease were underreported by more than 10,000 in a six-month period to the end of August, according to a government excess mortality report.

Source: Milenio (sp) 

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