Brazilians with COVID-19 symptoms are facing long lines to get tested due to the lack of kits in a country without a comprehensive testing strategy since the start of the pandemic.
Substantial testing and genomic sequencing of confirmed infections are crucial to tracking and fighting the pandemic, especially with the onset of the highly contagious omicron.
To make matters worse, some Health Ministry databases have been offline since an apparent ransomware attack on Dec 10 seriously hampered the government's ability to gather data from state health authorities.
"In general, the registration system was bad from the start, and it got worse with the hacker attack, so we're really under water," said Gonzalo Vecina, former head of Brazilian health regulator Anvisa and professor at the University of Sao Paulo.
"We're in the dark," he said.
Despite having the world's third-deadliest outbreak after the United States and Russia, according to Reuters calculations, Brazil tests for COVID-19 far less than South American peers.
Over the last seven days, Brazil performed an average 0.23 tests per 1,000 inhabitants, according to statistics compiled by the Our World in Data website. By contrast, Argentina applied 2.15 tests per 1,000 people in the same period and Uruguay performed 3.88 tests per 1,000 inhabitants.
Demand for tests in Brazil surged during year-end holidays and many pharmacies and clinics ran out of kits. Inventory had dwindled as vaccination advanced in the country and cases fell.
'AN EXPRESSIVE INCREASE'
Despite limited data sources, COVID-19 cases are clearly rising in Brazil.
In Rio de Janeiro, the rolling seven-day average of confirmed cases jumped more than 2,000% since mid-December to 398 on Monday.
"We are seeing an expressive increase in the number of cases, dealing with patients and people in everyday life. And this increase is happening in the places where omicron has been detected," said Esper Kallas, a doctor specialised in infectious diseases and professor at the University of Sao Paulo.
The Health Ministry did not respond to a request for comment on how the cyberattack affected monitoring of the pandemic. Health Minister Marcelo Queiroga has said that data is being collected but not made public.
The ministry's website was back online this week, but with numbers only through early December, before it was hacked.
Brazil has so far verified just 265 omicron cases since late November, according to the ministry. Extensive sequencing in other countries showed omicron quickly became the dominant variant, causing cases to surge in a matter of days.
The hope, experts say, is that omicron does not seem as lethal as previous variants and its death toll may be limited in Brazil, where a vaccination campaign has inoculated about two thirds of the population and booster shots are available.