A study using SARS-CoV-2 antibody and T-cell tests shows that 41% of 29 patients who developed a postviral syndrome (PVS) showed evidence of a previous COVID-19 infection, suggesting that millions of Americans with long COVID symptoms were exposed to the virus early in the pandemic but couldn't access testing.

Northwestern University researchers published the results yesterday in Neurology Neuroimmunology & Neuroinflammation.

The team measured SARS-CoV-2 humoral and cell-mediated immune responses against nucleocapsid and spike proteins in 29 PVS patients after suspected COVID-19, 32 age- and sex-matched neurologic long-COVID patients, and 18 uninfected controls. They retrospectively evaluated neurologic signs and symptoms, chronic conditions, quality of life, and cognitive testing data collected at clinic visits.

Potentially 4 million hidden long-COVID patients

Of 29 PVS patients, 12 (41%) had detectable humoral or cellular immune responses consistent with previous COVID-19 infection. Of the 12, 75% had anti-nucleocapsid responses, 50% had anti-spike responses, and all had similar neurologic symptoms as neurologic long-COVID patients but weren't clinically assessed an average 5.3 months later after symptom onset (10.7 vs 5.4 months).

PVS and neurologic long-COVID patients had similarly impaired quality of life, including worse cognitive function and fatigue. PVS patients had similar results in objective cognitive measures of processing speed, attention, and executive function but better working memory than neurologic long-COVID patients.

About 70% of post-COVID clinics in the U.S. do not accept people with long COVID symptoms who do not have a positive test result for COVID.

The study authors said the results highlight "the importance of multitargeted COVID-19 immunologic evaluation and the limitations of commercially available diagnostic tests."

They added that a lack of COVID-19 diagnosis probably delayed care for PVS patients. "Unlike our clinic, about 70% of post-COVID clinics in the U.S. do not accept people with long COVID symptoms who do not have a positive test result for COVID," senior author Igor Koralnik, MD, said in an American Academy of Neurology press release.

"Our data suggest that at least four million people with post-viral syndrome similar to long COVID may indeed have detectable immune responses to support a COVID diagnosis," he added. "More research is needed to confirm our findings."

Today in Morbidity and Mortality Weekly Report, researchers using the Centers for Disease Control and Prevention (CDC) arthropod-borne disease surveillance data confirm that West Nile virus remains the most common mosquito-borne disease in the United States, with almost 3,000 cases reported in 2021.

The surveillance data shows 3,035 cases of domestic arthropod-borne diseases, including 2,911 of West Nile, 40 cases of La Crosse, 32 cases of Jamestown Canyon, 24 cases of Powassan virus, 17 cases of St. Louis encephalitis, 5 cases of eastern equine encephalitis, and 6 cases of an unspecified California serogroup virus.

All cases were reported from all states except Hawaii and the District of Columbia, with 16% of all US counties reporting at least one case of arboviral disease.

Of the West Nile virus cases noted, 2,008 (69%) were classified as neuroinvasive, which included cases reporting encephalitis (64%), meningitis (30%), and acute flaccid paralysis (2%). Cases were reported from 432 counties in 49 states and the District of Columbia, with most seasonally reported (71%) during July, August, and September.

Arizona outbreak increased case counts

"Most patients with neuroinvasive disease (1,907; 95%) were hospitalized and 225 (11%) died," the authors wrote. Arizona had the largest number of neuroinvasive cases (1,140), or 57% of all US cases. The activity in Arizona made 2021 the most active year for West Nile in the United States since 2012.

"Reasons for the outbreak likely included late-season rain, recent population growth and housing development, and low levels of WNV [West Nile virus] circulation during the preceding year,” the authors wrote.

They said continued surveillance is needed, as there are no treatments for West Nile virus.

Global flu levels remain low, with activity leveling off in many Southern Hemisphere countries, the World Health Organization (WHO) said this week in its latest update, which covers roughly the last week of July and the first week of August.

Southeast Asia's flu levels remained elevated, including in Cambodia, Myanmar, and the Philippines, mainly due to a mix of influenza A strains. In South Asia, flu activity remained low in most of the region, except for Bangladesh and Bhutan. In East Asia, Hong Kong's activity remained near the epidemic threshold. However, today Hong Kong's Centre for Health Protection said local activity has increased over the past week, putting levels above the seasonal threshold and marking the start of its summer flu season.

In tropical Africa, flu activity increased in Ethiopia and Madagascar, but declined in other countries. Elsewhere, influenza B detections increased in Cuba.

Of respiratory samples that tested positive for flu at national flu labs during the surveillance period, 72.7% were influenza A, and of subtyped influenza A samples, 62.4% were the H3N2 strain and 37.6% were 2009 H1N1. Of characterized influenza B samples, all belonged to the Victoria lineage.

New data from Uganda indicate that artemisinin-resistant malaria is on the rise, researchers report today in the New England Journal of Medicine.

For the study, a team of researchers from Uganda and the United States performed annual surveillance among patients who presented with uncomplicated malaria caused by the Plasmodium falciparum parasite at 10 to 16 sites across Uganda from 2016 through 2022. They were looking to assess the prevalence of malaria isolates containing mutations in the kelch protein K13 (pfK13), which mediates partial resistance to artemisinin—the main component of the standard therapy for uncomplicated malaria across Africa. Partial resistance can delay parasite clearance.

Artemisinin and artemisinin combination therapies (ACTs) have greatly contributed to reductions in malaria deaths and complications, particularly in Africa, where 95% of malaria cases and deaths occur.

The analysis found that, by 2021-2022, the prevalence of parasites with validated or candidate resistance markers reached more than 20% in 11 of the 16 districts where surveillance was conducted. Two pfk13 mutations—469Y and 675V—reached a combined prevalence of 10% to 54% across much of northern Uganda, with spread to other regions, while the 469F mutation reached a prevalence of 38% to 40% in one district in southwestern Uganda in 2021-2022. Two other mutations (561H and 441L) also increased in prevalence in districts in southwestern and western Uganda.

Multiple PfK13 mutations, including five candidate or validated resistance markers, have shown increased prevalence and spread over time.

"Overall, multiple PfK13 mutations, including five candidate or validated resistance markers, have shown increased prevalence and spread over time," the study authors wrote.

Treatment could be compromised

The authors add that while the full clinical consequences of these genetic changes are not yet known, the experience in Southeast Asia, where resistance to artemisinin and ACTs has become widespread, suggests that malaria treatment in Uganda may be compromised.

"Improved characterization of the emergence and spread of artemisinin resistance and of factors that facilitate spread will assist policymakers in developing strategies to limit the spread and consequences of drug resistance," they wrote.

• Many older adults are aware of the new respiratory syncytial virus (RSV) vaccine, but interest in getting it varies by factors such as age and underlying health status, according to a new poll this week from the University of Michigan's Institute for Healthcare Policy and Innovation. Researchers gathered the data in July as part of the National Poll on Healthy Aging. Findings revealed that 52% had heard of the RSV vaccine, with 21% saying they're very interested in getting it and 43% responding that they're somewhat interested. People who rated their health good to excellent were more likely to have heard about the vaccine, and the team found that overall interest in the vaccine rose by age, which they said corresponds to the rising risk from the virus.
• Animal health experts yesterday warned about the risk of H5N1 avian flu spread to Antarctica's wildlife populations, as the virus continues to spread southward. A team from the World Organization for Animal Health and the UN Food and Agriculture Organization said the circulating H5N1 clade first turned up in South America in Colombia in October 2022 and has devastated wildlife in countries such as Peru and Chile. In just 3 months, the virus spread to the southern tip of South America, with the southernmost detection recently reported in a sea lion in Chile. The risk is substantial that the virus will continue southward to reach Antarctica and its offshore islands, especially with the spring migration of birds from South America to Antarctica. Though little can be done to stop the virus from spreading, the group urged scientists to document mortality events, limit amplification by removing carcasses, and follow biosecurity practices to reduce the risk of humans spreading the virus among the animal populations.
• In European avian flu developments, Finland recently reported another H5N1 outbreak at a fur farm, which involved a facility housing blue foxes, raising the number of outbreaks at such farms to 25. Also, the country began culling 120,000 foxes and mink at 13 affected fur farms, according to Agence France-Presse. Elsewhere, Russian veterinary officials have confirmed H5N1 in a seal found dead in Sakhalin oblast, according to an official statement translated and posted by Avian Flu Diary, an infectious disease news blog. Sakhalin oblast is in far eastern Russia, just north of Japan.